/*
* Copyright 2014 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkTextureCompressor_ASTC.h"
#include "SkTextureCompressor_Blitter.h"
#include "SkBlitter.h"
#include "SkEndian.h"
#include "SkMath.h"
// This table contains the weight values for each texel. This is used in determining
// how to convert a 12x12 grid of alpha values into a 6x5 grid of index values. Since
// we have a 6x5 grid, that gives 30 values that we have to compute. For each index,
// we store up to 20 different triplets of values. In order the triplets are:
// weight, texel-x, texel-y
// The weight value corresponds to the amount that this index contributes to the final
// index value of the given texel. Hence, we need to reconstruct the 6x5 index grid
// from their relative contribution to the 12x12 texel grid.
//
// The algorithm is something like this:
// foreach index i:
// total-weight = 0;
// total-alpha = 0;
// for w = 1 to 20:
// weight = table[i][w*3];
// texel-x = table[i][w*3 + 1];
// texel-y = table[i][w*3 + 2];
// if weight >= 0:
// total-weight += weight;
// total-alpha += weight * alphas[texel-x][texel-y];
//
// total-alpha /= total-weight;
// index = top three bits of total-alpha
//
// If the associated index does not contribute to 20 different texels (e.g. it's in
// a corner), then the extra texels are stored with -1's in the table.
static const int8_t k6x5To12x12Table[30][60] = {
{ 16, 0, 0, 9, 1, 0, 1, 2, 0, 10, 0, 1, 6, 1, 1, 1, 2, 1, 4, 0, 2, 2,
1, 2, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 7, 1, 0, 15, 2, 0, 10, 3, 0, 3, 4, 0, 4, 1, 1, 9, 2, 1, 6, 3, 1, 2,
4, 1, 2, 1, 2, 4, 2, 2, 3, 3, 2, 1, 4, 2, -1, 0, 0, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 6, 3, 0, 13, 4, 0, 12, 5, 0, 4, 6, 0, 4, 3, 1, 8, 4, 1, 8, 5, 1, 3,
6, 1, 1, 3, 2, 3, 4, 2, 3, 5, 2, 1, 6, 2, -1, 0, 0, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 4, 5, 0, 12, 6, 0, 13, 7, 0, 6, 8, 0, 2, 5, 1, 7, 6, 1, 8, 7, 1, 4,
8, 1, 1, 5, 2, 3, 6, 2, 3, 7, 2, 2, 8, 2, -1, 0, 0, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 3, 7, 0, 10, 8, 0, 15, 9, 0, 7, 10, 0, 2, 7, 1, 6, 8, 1, 9, 9, 1, 4,
10, 1, 1, 7, 2, 2, 8, 2, 4, 9, 2, 2, 10, 2, -1, 0, 0, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 1, 9, 0, 9, 10, 0, 16, 11, 0, 1, 9, 1, 6, 10, 1, 10, 11, 1, 2, 10, 2, 4,
11, 2, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 6, 0, 1, 3, 1, 1, 12, 0, 2, 7, 1, 2, 1, 2, 2, 15, 0, 3, 8, 1, 3, 1,
2, 3, 9, 0, 4, 5, 1, 4, 1, 2, 4, 3, 0, 5, 2, 1, 5, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 3, 1, 1, 6, 2, 1, 4, 3, 1, 1, 4, 1, 5, 1, 2, 11, 2, 2, 7, 3, 2, 2,
4, 2, 7, 1, 3, 14, 2, 3, 9, 3, 3, 3, 4, 3, 4, 1, 4, 8, 2, 4, 6, 3,
4, 2, 4, 4, 1, 1, 5, 3, 2, 5, 2, 3, 5, 1, 4, 5}, // n = 20
{ 2, 3, 1, 5, 4, 1, 4, 5, 1, 1, 6, 1, 5, 3, 2, 10, 4, 2, 9, 5, 2, 3,
6, 2, 6, 3, 3, 12, 4, 3, 11, 5, 3, 4, 6, 3, 3, 3, 4, 7, 4, 4, 7, 5,
4, 2, 6, 4, 1, 3, 5, 2, 4, 5, 2, 5, 5, 1, 6, 5}, // n = 20
{ 2, 5, 1, 5, 6, 1, 5, 7, 1, 2, 8, 1, 3, 5, 2, 9, 6, 2, 10, 7, 2, 4,
8, 2, 4, 5, 3, 11, 6, 3, 12, 7, 3, 6, 8, 3, 2, 5, 4, 7, 6, 4, 7, 7,
4, 3, 8, 4, 1, 5, 5, 2, 6, 5, 2, 7, 5, 1, 8, 5}, // n = 20
{ 1, 7, 1, 4, 8, 1, 6, 9, 1, 3, 10, 1, 2, 7, 2, 8, 8, 2, 11, 9, 2, 5,
10, 2, 3, 7, 3, 9, 8, 3, 14, 9, 3, 7, 10, 3, 2, 7, 4, 6, 8, 4, 8, 9,
4, 4, 10, 4, 1, 7, 5, 2, 8, 5, 3, 9, 5, 1, 10, 5}, // n = 20
{ 3, 10, 1, 6, 11, 1, 1, 9, 2, 7, 10, 2, 12, 11, 2, 1, 9, 3, 8, 10, 3, 15,
11, 3, 1, 9, 4, 5, 10, 4, 9, 11, 4, 2, 10, 5, 3, 11, 5, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 1, 0, 3, 1, 1, 3, 7, 0, 4, 4, 1, 4, 13, 0, 5, 7, 1, 5, 1, 2, 5, 13,
0, 6, 7, 1, 6, 1, 2, 6, 7, 0, 7, 4, 1, 7, 1, 0, 8, 1, 1, 8, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 1, 2, 3, 1, 3, 3, 3, 1, 4, 7, 2, 4, 4, 3, 4, 1, 4, 4, 6, 1, 5, 12,
2, 5, 8, 3, 5, 2, 4, 5, 6, 1, 6, 12, 2, 6, 8, 3, 6, 2, 4, 6, 3, 1,
7, 7, 2, 7, 4, 3, 7, 1, 4, 7, 1, 2, 8, 1, 3, 8}, // n = 20
{ 1, 4, 3, 1, 5, 3, 3, 3, 4, 6, 4, 4, 5, 5, 4, 2, 6, 4, 5, 3, 5, 11,
4, 5, 10, 5, 5, 3, 6, 5, 5, 3, 6, 11, 4, 6, 10, 5, 6, 3, 6, 6, 3, 3,
7, 6, 4, 7, 5, 5, 7, 2, 6, 7, 1, 4, 8, 1, 5, 8}, // n = 20
{ 1, 6, 3, 1, 7, 3, 2, 5, 4, 5, 6, 4, 6, 7, 4, 3, 8, 4, 3, 5, 5, 10,
6, 5, 11, 7, 5, 5, 8, 5, 3, 5, 6, 10, 6, 6, 11, 7, 6, 5, 8, 6, 2, 5,
7, 5, 6, 7, 6, 7, 7, 3, 8, 7, 1, 6, 8, 1, 7, 8}, // n = 20
{ 1, 8, 3, 1, 9, 3, 1, 7, 4, 4, 8, 4, 7, 9, 4, 3, 10, 4, 2, 7, 5, 8,
8, 5, 12, 9, 5, 6, 10, 5, 2, 7, 6, 8, 8, 6, 12, 9, 6, 6, 10, 6, 1, 7,
7, 4, 8, 7, 7, 9, 7, 3, 10, 7, 1, 8, 8, 1, 9, 8}, // n = 20
{ 1, 10, 3, 1, 11, 3, 4, 10, 4, 7, 11, 4, 1, 9, 5, 7, 10, 5, 13, 11, 5, 1,
9, 6, 7, 10, 6, 13, 11, 6, 4, 10, 7, 7, 11, 7, 1, 10, 8, 1, 11, 8, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 3, 0, 6, 2, 1, 6, 9, 0, 7, 5, 1, 7, 1, 2, 7, 15, 0, 8, 8, 1, 8, 1,
2, 8, 12, 0, 9, 7, 1, 9, 1, 2, 9, 6, 0, 10, 3, 1, 10, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 1, 1, 6, 3, 2, 6, 2, 3, 6, 1, 4, 6, 4, 1, 7, 8, 2, 7, 6, 3, 7, 2,
4, 7, 7, 1, 8, 14, 2, 8, 9, 3, 8, 3, 4, 8, 5, 1, 9, 11, 2, 9, 8, 3,
9, 2, 4, 9, 3, 1, 10, 6, 2, 10, 4, 3, 10, 1, 4, 10}, // n = 20
{ 1, 3, 6, 2, 4, 6, 2, 5, 6, 1, 6, 6, 3, 3, 7, 7, 4, 7, 7, 5, 7, 2,
6, 7, 6, 3, 8, 12, 4, 8, 11, 5, 8, 4, 6, 8, 4, 3, 9, 10, 4, 9, 9, 5,
9, 3, 6, 9, 2, 3, 10, 5, 4, 10, 5, 5, 10, 2, 6, 10}, // n = 20
{ 1, 5, 6, 2, 6, 6, 2, 7, 6, 1, 8, 6, 2, 5, 7, 7, 6, 7, 7, 7, 7, 3,
8, 7, 4, 5, 8, 11, 6, 8, 12, 7, 8, 6, 8, 8, 3, 5, 9, 9, 6, 9, 10, 7,
9, 5, 8, 9, 1, 5, 10, 4, 6, 10, 5, 7, 10, 2, 8, 10}, // n = 20
{ 1, 7, 6, 2, 8, 6, 3, 9, 6, 1, 10, 6, 2, 7, 7, 6, 8, 7, 8, 9, 7, 4,
10, 7, 3, 7, 8, 9, 8, 8, 14, 9, 8, 7, 10, 8, 2, 7, 9, 7, 8, 9, 11, 9,
9, 5, 10, 9, 1, 7, 10, 4, 8, 10, 6, 9, 10, 3, 10, 10}, // n = 20
{ 2, 10, 6, 3, 11, 6, 1, 9, 7, 5, 10, 7, 9, 11, 7, 1, 9, 8, 8, 10, 8, 15,
11, 8, 1, 9, 9, 7, 10, 9, 12, 11, 9, 3, 10, 10, 6, 11, 10, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 4, 0, 9, 2, 1, 9, 10, 0, 10, 6, 1, 10, 1, 2, 10, 16, 0, 11, 9, 1, 11, 1,
2, 11, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 2, 1, 9, 4, 2, 9, 2, 3, 9, 1, 4, 9, 4, 1, 10, 9, 2, 10, 6, 3, 10, 2,
4, 10, 7, 1, 11, 15, 2, 11, 10, 3, 11, 3, 4, 11, -1, 0, 0, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 2, 3, 9, 3, 4, 9, 3, 5, 9, 1, 6, 9, 4, 3, 10, 8, 4, 10, 7, 5, 10, 2,
6, 10, 6, 3, 11, 13, 4, 11, 12, 5, 11, 4, 6, 11, -1, 0, 0, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 1, 5, 9, 3, 6, 9, 3, 7, 9, 1, 8, 9, 3, 5, 10, 8, 6, 10, 8, 7, 10, 4,
8, 10, 4, 5, 11, 12, 6, 11, 13, 7, 11, 6, 8, 11, -1, 0, 0, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 1, 7, 9, 3, 8, 9, 4, 9, 9, 2, 10, 9, 2, 7, 10, 6, 8, 10, 9, 9, 10, 4,
10, 10, 3, 7, 11, 10, 8, 11, 15, 9, 11, 7, 10, 11, -1, 0, 0, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0}, // n = 20
{ 2, 10, 9, 4, 11, 9, 1, 9, 10, 6, 10, 10, 10, 11, 10, 1, 9, 11, 9, 10, 11, 16,
11, 11, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0,
0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0} // n = 20
};
// Returns the alpha value of a texel at position (x, y) from src.
// (x, y) are assumed to be in the range [0, 12).
inline uint8_t GetAlpha(const uint8_t *src, size_t rowBytes, int x, int y) {
SkASSERT(x >= 0 && x < 12);
SkASSERT(y >= 0 && y < 12);
SkASSERT(rowBytes >= 12);
return *(src + y*rowBytes + x);
}
inline uint8_t GetAlphaTranspose(const uint8_t *src, size_t rowBytes, int x, int y) {
return GetAlpha(src, rowBytes, y, x);
}
// Output the 16 bytes stored in top and bottom and advance the pointer. The bytes
// are stored as the integers are represented in memory, so they should be swapped
// if necessary.
static inline void send_packing(uint8_t** dst, const uint64_t top, const uint64_t bottom) {
uint64_t* dst64 = reinterpret_cast<uint64_t*>(*dst);
dst64[0] = top;
dst64[1] = bottom;
*dst += 16;
}
// Compresses an ASTC block, by looking up the proper contributions from
// k6x5To12x12Table and computing an index from the associated values.
typedef uint8_t (*GetAlphaProc)(const uint8_t* src, size_t rowBytes, int x, int y);
template<GetAlphaProc getAlphaProc>
static void compress_a8_astc_block(uint8_t** dst, const uint8_t* src, size_t rowBytes) {
// Check for single color
bool constant = true;
const uint32_t firstInt = *(reinterpret_cast<const uint32_t*>(src));
for (int i = 0; i < 12; ++i) {
const uint32_t *rowInt = reinterpret_cast<const uint32_t *>(src + i*rowBytes);
constant = constant && (rowInt[0] == firstInt);
constant = constant && (rowInt[1] == firstInt);
constant = constant && (rowInt[2] == firstInt);
}
if (constant) {
if (0 == firstInt) {
// All of the indices are set to zero, and the colors are
// v0 = 0, v1 = 255, so everything will be transparent.
send_packing(dst, SkTEndian_SwapLE64(0x0000000001FE000173ULL), 0);
return;
} else if (0xFFFFFFFF == firstInt) {
// All of the indices are set to zero, and the colors are
// v0 = 255, v1 = 0, so everything will be opaque.
send_packing(dst, SkTEndian_SwapLE64(0x000000000001FE0173ULL), 0);
return;
}
}
uint8_t indices[30]; // 6x5 index grid
for (int idx = 0; idx < 30; ++idx) {
int weightTot = 0;
int alphaTot = 0;
for (int w = 0; w < 20; ++w) {
const int8_t weight = k6x5To12x12Table[idx][w*3];
if (weight > 0) {
const int x = k6x5To12x12Table[idx][w*3 + 1];
const int y = k6x5To12x12Table[idx][w*3 + 2];
weightTot += weight;
alphaTot += weight * getAlphaProc(src, rowBytes, x, y);
} else {
// In our table, not every entry has 20 weights, and all
// of them are nonzero. Once we hit a negative weight, we
// know that all of the other weights are not valid either.
break;
}
}
indices[idx] = (alphaTot / weightTot) >> 5;
}
// Pack indices... The ASTC block layout is fairly complicated. An extensive
// description can be found here:
// https://www.opengl.org/registry/specs/KHR/texture_compression_astc_hdr.txt
//
// Here is a summary of the options that we've chosen:
// 1. Block mode: 0b00101110011
// - 6x5 texel grid
// - Single plane
// - Low-precision index values
// - Index range 0-7 (three bits per index)
// 2. Partitions: 0b00
// - One partition
// 3. Color Endpoint Mode: 0b0000
// - Direct luminance -- e0=(v0,v0,v0,0xFF); e1=(v1,v1,v1,0xFF);
// 4. 8-bit endpoints:
// v0 = 0, v1 = 255
//
// The rest of the block contains the 30 index values from before, which
// are currently stored in the indices variable.
uint64_t top = 0x0000000001FE000173ULL;
uint64_t bottom = 0;
for (int idx = 0; idx <= 20; ++idx) {
const uint8_t index = indices[idx];
bottom |= static_cast<uint64_t>(index) << (61-(idx*3));
}
// index 21 straddles top and bottom
{
const uint8_t index = indices[21];
bottom |= index & 1;
top |= static_cast<uint64_t>((index >> 2) | (index & 2)) << 62;
}
for (int idx = 22; idx < 30; ++idx) {
const uint8_t index = indices[idx];
top |= static_cast<uint64_t>(index) << (59-(idx-22)*3);
}
// Reverse each 3-bit index since indices are read in reverse order...
uint64_t t = (bottom ^ (bottom >> 2)) & 0x2492492492492492ULL;
bottom = bottom ^ t ^ (t << 2);
t = (top ^ (top >> 2)) & 0x0924924000000000ULL;
top = top ^ t ^ (t << 2);
send_packing(dst, SkEndian_SwapLE64(top), SkEndian_SwapLE64(bottom));
}
inline void CompressA8ASTCBlockVertical(uint8_t* dst, const uint8_t* src) {
compress_a8_astc_block<GetAlphaTranspose>(&dst, src, 12);
}
////////////////////////////////////////////////////////////////////////////////
//
// ASTC Decoder
//
// Full details available in the spec:
// http://www.khronos.org/registry/gles/extensions/OES/OES_texture_compression_astc.txt
//
////////////////////////////////////////////////////////////////////////////////
// Enable this to assert whenever a decoded block has invalid ASTC values. Otherwise,
// each invalid block will result in a disgusting magenta color.
#define ASSERT_ASTC_DECODE_ERROR 0
// Reverse 64-bit integer taken from TAOCP 4a, although it's better
// documented at this site:
// http://matthewarcus.wordpress.com/2012/11/18/reversing-a-64-bit-word/
template <typename T, T m, int k>
static inline T swap_bits(T p) {
T q = ((p>>k)^p) & m;
return p^q^(q<<k);
}
static inline uint64_t reverse64(uint64_t n) {
static const uint64_t m0 = 0x5555555555555555ULL;
static const uint64_t m1 = 0x0300c0303030c303ULL;
static const uint64_t m2 = 0x00c0300c03f0003fULL;
static const uint64_t m3 = 0x00000ffc00003fffULL;
n = ((n>>1)&m0) | (n&m0)<<1;
n = swap_bits<uint64_t, m1, 4>(n);
n = swap_bits<uint64_t, m2, 8>(n);
n = swap_bits<uint64_t, m3, 20>(n);
n = (n >> 34) | (n << 30);
return n;
}
// An ASTC block is 128 bits. We represent it as two 64-bit integers in order
// to efficiently operate on the block using bitwise operations.
struct ASTCBlock {
uint64_t fLow;
uint64_t fHigh;
// Reverses the bits of an ASTC block, making the LSB of the
// 128 bit block the MSB.
inline void reverse() {
const uint64_t newLow = reverse64(this->fHigh);
this->fHigh = reverse64(this->fLow);
this->fLow = newLow;
}
};
// Writes the given color to every pixel in the block. This is used by void-extent
// blocks (a special constant-color encoding of a block) and by the error function.
static inline void write_constant_color(uint8_t* dst, int blockDimX, int blockDimY,
int dstRowBytes, SkColor color) {
for (int y = 0; y < blockDimY; ++y) {
SkColor *dstColors = reinterpret_cast<SkColor*>(dst);
for (int x = 0; x < blockDimX; ++x) {
dstColors[x] = color;
}
dst += dstRowBytes;
}
}
// Sets the entire block to the ASTC "error" color, a disgusting magenta
// that's not supposed to appear in natural images.
static inline void write_error_color(uint8_t* dst, int blockDimX, int blockDimY,
int dstRowBytes) {
static const SkColor kASTCErrorColor = SkColorSetRGB(0xFF, 0, 0xFF);
#if ASSERT_ASTC_DECODE_ERROR
SkDEBUGFAIL("ASTC decoding error!\n");
#endif
write_constant_color(dst, blockDimX, blockDimY, dstRowBytes, kASTCErrorColor);
}
// Reads up to 64 bits of the ASTC block starting from bit
// 'from' and going up to but not including bit 'to'. 'from' starts
// counting from the LSB, counting up to the MSB. Returns -1 on
// error.
static uint64_t read_astc_bits(const ASTCBlock &block, int from, int to) {
SkASSERT(0 <= from && from <= 128);
SkASSERT(0 <= to && to <= 128);
const int nBits = to - from;
if (0 == nBits) {
return 0;
}
if (nBits < 0 || 64 <= nBits) {
SkDEBUGFAIL("ASTC -- shouldn't read more than 64 bits");
return -1;
}
// Remember, the 'to' bit isn't read.
uint64_t result = 0;
if (to <= 64) {
// All desired bits are in the low 64-bits.
result = (block.fLow >> from) & ((1ULL << nBits) - 1);
} else if (from >= 64) {
// All desired bits are in the high 64-bits.
result = (block.fHigh >> (from - 64)) & ((1ULL << nBits) - 1);
} else {
// from < 64 && to > 64
SkASSERT(nBits > (64 - from));
const int nLow = 64 - from;
const int nHigh = nBits - nLow;
result =
((block.fLow >> from) & ((1ULL << nLow) - 1)) |
((block.fHigh & ((1ULL << nHigh) - 1)) << nLow);
}
return result;
}
// Returns the number of bits needed to represent a number
// in the given power-of-two range (excluding the power of two itself).
static inline int bits_for_range(int x) {
SkASSERT(SkIsPow2(x));
SkASSERT(0 != x);
// Since we know it's a power of two, there should only be one bit set,
// meaning the number of trailing zeros is 31 minus the number of leading
// zeros.
return 31 - SkCLZ(x);
}
// Clamps an integer to the range [0, 255]
static inline int clamp_byte(int x) {
return SkClampMax(x, 255);
}
// Helper function defined in the ASTC spec, section C.2.14
// It transfers a few bits of precision from one value to another.
static inline void bit_transfer_signed(int *a, int *b) {
*b >>= 1;
*b |= *a & 0x80;
*a >>= 1;
*a &= 0x3F;
if ( (*a & 0x20) != 0 ) {
*a -= 0x40;
}
}
// Helper function defined in the ASTC spec, section C.2.14
// It uses the value in the blue channel to tint the red and green
static inline SkColor blue_contract(int a, int r, int g, int b) {
return SkColorSetARGB(a, (r + b) >> 1, (g + b) >> 1, b);
}
// Helper function that decodes two colors from eight values. If isRGB is true,
// then the pointer 'v' contains six values and the last two are considered to be
// 0xFF. If isRGB is false, then all eight values come from the pointer 'v'. This
// corresponds to the decode procedure for the following endpoint modes:
// kLDR_RGB_Direct_ColorEndpointMode
// kLDR_RGBA_Direct_ColorEndpointMode
static inline void decode_rgba_direct(const int *v, SkColor *endpoints, bool isRGB) {
int v6 = 0xFF;
int v7 = 0xFF;
if (!isRGB) {
v6 = v[6];
v7 = v[7];
}
const int s0 = v[0] + v[2] + v[4];
const int s1 = v[1] + v[3] + v[5];
if (s1 >= s0) {
endpoints[0] = SkColorSetARGB(v6, v[0], v[2], v[4]);
endpoints[1] = SkColorSetARGB(v7, v[1], v[3], v[5]);
} else {
endpoints[0] = blue_contract(v7, v[1], v[3], v[5]);
endpoints[1] = blue_contract(v6, v[0], v[2], v[4]);
}
}
// Helper function that decodes two colors from six values. If isRGB is true,
// then the pointer 'v' contains four values and the last two are considered to be
// 0xFF. If isRGB is false, then all six values come from the pointer 'v'. This
// corresponds to the decode procedure for the following endpoint modes:
// kLDR_RGB_BaseScale_ColorEndpointMode
// kLDR_RGB_BaseScaleWithAlpha_ColorEndpointMode
static inline void decode_rgba_basescale(const int *v, SkColor *endpoints, bool isRGB) {
int v4 = 0xFF;
int v5 = 0xFF;
if (!isRGB) {
v4 = v[4];
v5 = v[5];
}
endpoints[0] = SkColorSetARGB(v4,
(v[0]*v[3]) >> 8,
(v[1]*v[3]) >> 8,
(v[2]*v[3]) >> 8);
endpoints[1] = SkColorSetARGB(v5, v[0], v[1], v[2]);
}
// Helper function that decodes two colors from eight values. If isRGB is true,
// then the pointer 'v' contains six values and the last two are considered to be
// 0xFF. If isRGB is false, then all eight values come from the pointer 'v'. This
// corresponds to the decode procedure for the following endpoint modes:
// kLDR_RGB_BaseOffset_ColorEndpointMode
// kLDR_RGBA_BaseOffset_ColorEndpointMode
//
// If isRGB is true, then treat this as if v6 and v7 are meant to encode full alpha values.
static inline void decode_rgba_baseoffset(const int *v, SkColor *endpoints, bool isRGB) {
int v0 = v[0];
int v1 = v[1];
int v2 = v[2];
int v3 = v[3];
int v4 = v[4];
int v5 = v[5];
int v6 = isRGB ? 0xFF : v[6];
// The 0 is here because this is an offset, not a direct value
int v7 = isRGB ? 0 : v[7];
bit_transfer_signed(&v1, &v0);
bit_transfer_signed(&v3, &v2);
bit_transfer_signed(&v5, &v4);
if (!isRGB) {
bit_transfer_signed(&v7, &v6);
}
int c[2][4];
if ((v1 + v3 + v5) >= 0) {
c[0][0] = v6;
c[0][1] = v0;
c[0][2] = v2;
c[0][3] = v4;
c[1][0] = v6 + v7;
c[1][1] = v0 + v1;
c[1][2] = v2 + v3;
c[1][3] = v4 + v5;
} else {
c[0][0] = v6 + v7;
c[0][1] = (v0 + v1 + v4 + v5) >> 1;
c[0][2] = (v2 + v3 + v4 + v5) >> 1;
c[0][3] = v4 + v5;
c[1][0] = v6;
c[1][1] = (v0 + v4) >> 1;
c[1][2] = (v2 + v4) >> 1;
c[1][3] = v4;
}
endpoints[0] = SkColorSetARGB(clamp_byte(c[0][0]),
clamp_byte(c[0][1]),
clamp_byte(c[0][2]),
clamp_byte(c[0][3]));
endpoints[1] = SkColorSetARGB(clamp_byte(c[1][0]),
clamp_byte(c[1][1]),
clamp_byte(c[1][2]),
clamp_byte(c[1][3]));
}
// A helper class used to decode bit values from standard integer values.
// We can't use this class with ASTCBlock because then it would need to
// handle multi-value ranges, and it's non-trivial to lookup a range of bits
// that splits across two different ints.
template <typename T>
class SkTBits {
public:
SkTBits(const T val) : fVal(val) { }
// Returns the bit at the given position
T operator [](const int idx) const {
return (fVal >> idx) & 1;
}
// Returns the bits in the given range, inclusive
T operator ()(const int end, const int start) const {
SkASSERT(end >= start);
return (fVal >> start) & ((1ULL << ((end - start) + 1)) - 1);
}
private:
const T fVal;
};
// This algorithm matches the trit block decoding in the spec (Table C.2.14)
static void decode_trit_block(int* dst, int nBits, const uint64_t &block) {
SkTBits<uint64_t> blockBits(block);
// According to the spec, a trit block, which contains five values,
// has the following layout:
//
// 27 26 25 24 23 22 21 20 19 18 17 16
// -----------------------------------------------
// |T7 | m4 |T6 T5 | m3 |T4 |
// -----------------------------------------------
//
// 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
// --------------------------------------------------------------
// | m2 |T3 T2 | m1 |T1 T0 | m0 |
// --------------------------------------------------------------
//
// Where the m's are variable width depending on the number of bits used
// to encode the values (anywhere from 0 to 6). Since 3^5 = 243, the extra
// byte labeled T (whose bits are interleaved where 0 is the LSB and 7 is
// the MSB), contains five trit values. To decode the trit values, the spec
// says that we need to follow the following algorithm:
//
// if T[4:2] = 111
// C = { T[7:5], T[1:0] }; t4 = t3 = 2
// else
// C = T[4:0]
//
// if T[6:5] = 11
// t4 = 2; t3 = T[7]
// else
// t4 = T[7]; t3 = T[6:5]
//
// if C[1:0] = 11
// t2 = 2; t1 = C[4]; t0 = { C[3], C[2]&~C[3] }
// else if C[3:2] = 11
// t2 = 2; t1 = 2; t0 = C[1:0]
// else
// t2 = C[4]; t1 = C[3:2]; t0 = { C[1], C[0]&~C[1] }
//
// The following C++ code is meant to mirror this layout and algorithm as
// closely as possible.
int m[5];
if (0 == nBits) {
memset(m, 0, sizeof(m));
} else {
SkASSERT(nBits < 8);
m[0] = static_cast<int>(blockBits(nBits - 1, 0));
m[1] = static_cast<int>(blockBits(2*nBits - 1 + 2, nBits + 2));
m[2] = static_cast<int>(blockBits(3*nBits - 1 + 4, 2*nBits + 4));
m[3] = static_cast<int>(blockBits(4*nBits - 1 + 5, 3*nBits + 5));
m[4] = static_cast<int>(blockBits(5*nBits - 1 + 7, 4*nBits + 7));
}
int T =
static_cast<int>(blockBits(nBits + 1, nBits)) |
(static_cast<int>(blockBits(2*nBits + 2 + 1, 2*nBits + 2)) << 2) |
(static_cast<int>(blockBits[3*nBits + 4] << 4)) |
(static_cast<int>(blockBits(4*nBits + 5 + 1, 4*nBits + 5)) << 5) |
(static_cast<int>(blockBits[5*nBits + 7] << 7));
int t[5];
int C;
SkTBits<int> Tbits(T);
if (0x7 == Tbits(4, 2)) {
C = (Tbits(7, 5) << 2) | Tbits(1, 0);
t[3] = t[4] = 2;
} else {
C = Tbits(4, 0);
if (Tbits(6, 5) == 0x3) {
t[4] = 2; t[3] = Tbits[7];
} else {
t[4] = Tbits[7]; t[3] = Tbits(6, 5);
}
}
SkTBits<int> Cbits(C);
if (Cbits(1, 0) == 0x3) {
t[2] = 2;
t[1] = Cbits[4];
t[0] = (Cbits[3] << 1) | (Cbits[2] & (0x1 & ~(Cbits[3])));
} else if (Cbits(3, 2) == 0x3) {
t[2] = 2;
t[1] = 2;
t[0] = Cbits(1, 0);
} else {
t[2] = Cbits[4];
t[1] = Cbits(3, 2);
t[0] = (Cbits[1] << 1) | (Cbits[0] & (0x1 & ~(Cbits[1])));
}
#ifdef SK_DEBUG
// Make sure all of the decoded values have a trit less than three
// and a bit value within the range of the allocated bits.
for (int i = 0; i < 5; ++i) {
SkASSERT(t[i] < 3);
SkASSERT(m[i] < (1 << nBits));
}
#endif
for (int i = 0; i < 5; ++i) {
*dst = (t[i] << nBits) + m[i];
++dst;
}
}
// This algorithm matches the quint block decoding in the spec (Table C.2.15)
static void decode_quint_block(int* dst, int nBits, const uint64_t &block) {
SkTBits<uint64_t> blockBits(block);
// According to the spec, a quint block, which contains three values,
// has the following layout:
//
//
// 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
// --------------------------------------------------------------------------
// |Q6 Q5 | m2 |Q4 Q3 | m1 |Q2 Q1 Q0 | m0 |
// --------------------------------------------------------------------------
//
// Where the m's are variable width depending on the number of bits used
// to encode the values (anywhere from 0 to 4). Since 5^3 = 125, the extra
// 7-bit value labeled Q (whose bits are interleaved where 0 is the LSB and 6 is
// the MSB), contains three quint values. To decode the quint values, the spec
// says that we need to follow the following algorithm:
//
// if Q[2:1] = 11 and Q[6:5] = 00
// q2 = { Q[0], Q[4]&~Q[0], Q[3]&~Q[0] }; q1 = q0 = 4
// else
// if Q[2:1] = 11
// q2 = 4; C = { Q[4:3], ~Q[6:5], Q[0] }
// else
// q2 = T[6:5]; C = Q[4:0]
//
// if C[2:0] = 101
// q1 = 4; q0 = C[4:3]
// else
// q1 = C[4:3]; q0 = C[2:0]
//
// The following C++ code is meant to mirror this layout and algorithm as
// closely as possible.
int m[3];
if (0 == nBits) {
memset(m, 0, sizeof(m));
} else {
SkASSERT(nBits < 8);
m[0] = static_cast<int>(blockBits(nBits - 1, 0));
m[1] = static_cast<int>(blockBits(2*nBits - 1 + 3, nBits + 3));
m[2] = static_cast<int>(blockBits(3*nBits - 1 + 5, 2*nBits + 5));
}
int Q =
static_cast<int>(blockBits(nBits + 2, nBits)) |
(static_cast<int>(blockBits(2*nBits + 3 + 1, 2*nBits + 3)) << 3) |
(static_cast<int>(blockBits(3*nBits + 5 + 1, 3*nBits + 5)) << 5);
int q[3];
SkTBits<int> Qbits(Q); // quantum?
if (Qbits(2, 1) == 0x3 && Qbits(6, 5) == 0) {
const int notBitZero = (0x1 & ~(Qbits[0]));
q[2] = (Qbits[0] << 2) | ((Qbits[4] & notBitZero) << 1) | (Qbits[3] & notBitZero);
q[1] = 4;
q[0] = 4;
} else {
int C;
if (Qbits(2, 1) == 0x3) {
q[2] = 4;
C = (Qbits(4, 3) << 3) | ((0x3 & ~(Qbits(6, 5))) << 1) | Qbits[0];
} else {
q[2] = Qbits(6, 5);
C = Qbits(4, 0);
}
SkTBits<int> Cbits(C);
if (Cbits(2, 0) == 0x5) {
q[1] = 4;
q[0] = Cbits(4, 3);
} else {
q[1] = Cbits(4, 3);
q[0] = Cbits(2, 0);
}
}
#ifdef SK_DEBUG
for (int i = 0; i < 3; ++i) {
SkASSERT(q[i] < 5);
SkASSERT(m[i] < (1 << nBits));
}
#endif
for (int i = 0; i < 3; ++i) {
*dst = (q[i] << nBits) + m[i];
++dst;
}
}
// Function that decodes a sequence of integers stored as an ISE (Integer
// Sequence Encoding) bit stream. The full details of this function are outlined
// in section C.2.12 of the ASTC spec. A brief overview is as follows:
//
// - Each integer in the sequence is bounded by a specific range r.
// - The range of each value determines the way the bit stream is interpreted,
// - If the range is a power of two, then the sequence is a sequence of bits
// - If the range is of the form 3*2^n, then the sequence is stored as a
// sequence of blocks, each block contains 5 trits and 5 bit sequences, which
// decodes into 5 values.
// - Similarly, if the range is of the form 5*2^n, then the sequence is stored as a
// sequence of blocks, each block contains 3 quints and 3 bit sequences, which
// decodes into 3 values.
static bool decode_integer_sequence(
int* dst, // The array holding the destination bits
int dstSize, // The maximum size of the array
int nVals, // The number of values that we'd like to decode
const ASTCBlock &block, // The block that we're decoding from
int startBit, // The bit from which we're going to do the reading
int endBit, // The bit at which we stop reading (not inclusive)
bool bReadForward, // If true, then read LSB -> MSB, else read MSB -> LSB
int nBits, // The number of bits representing this encoding
int nTrits, // The number of trits representing this encoding
int nQuints // The number of quints representing this encoding
) {
// If we want more values than we have, then fail.
if (nVals > dstSize) {
return false;
}
ASTCBlock src = block;
if (!bReadForward) {
src.reverse();
startBit = 128 - startBit;
endBit = 128 - endBit;
}
while (nVals > 0) {
if (nTrits > 0) {
SkASSERT(0 == nQuints);
int endBlockBit = startBit + 8 + 5*nBits;
if (endBlockBit > endBit) {
endBlockBit = endBit;
}
// Trit blocks are three values large.
int trits[5];
decode_trit_block(trits, nBits, read_astc_bits(src, startBit, endBlockBit));
memcpy(dst, trits, SkMin32(nVals, 5)*sizeof(int));
dst += 5;
nVals -= 5;
startBit = endBlockBit;
} else if (nQuints > 0) {
SkASSERT(0 == nTrits);
int endBlockBit = startBit + 7 + 3*nBits;
if (endBlockBit > endBit) {
endBlockBit = endBit;
}
// Quint blocks are three values large
int quints[3];
decode_quint_block(quints, nBits, read_astc_bits(src, startBit, endBlockBit));
memcpy(dst, quints, SkMin32(nVals, 3)*sizeof(int));
dst += 3;
nVals -= 3;
startBit = endBlockBit;
} else {
// Just read the bits, but don't read more than we have...
int endValBit = startBit + nBits;
if (endValBit > endBit) {
endValBit = endBit;
}
SkASSERT(endValBit - startBit < 31);
*dst = static_cast<int>(read_astc_bits(src, startBit, endValBit));
++dst;
--nVals;
startBit = endValBit;
}
}
return true;
}
// Helper function that unquantizes some (seemingly random) generated
// numbers... meant to match the ASTC hardware. This function is used
// to unquantize both colors (Table C.2.16) and weights (Table C.2.26)
static inline int unquantize_value(unsigned mask, int A, int B, int C, int D) {
int T = D * C + B;
T = T ^ A;
T = (A & mask) | (T >> 2);
SkASSERT(T < 256);
return T;
}
// Helper function to replicate the bits in x that represents an oldPrec
// precision integer into a prec precision integer. For example:
// 255 == replicate_bits(7, 3, 8);
static inline int replicate_bits(int x, int oldPrec, int prec) {
while (oldPrec < prec) {
const int toShift = SkMin32(prec-oldPrec, oldPrec);
x = (x << toShift) | (x >> (oldPrec - toShift));
oldPrec += toShift;
}
// Make sure that no bits are set outside the desired precision.
SkASSERT((-(1 << prec) & x) == 0);
return x;
}
// Returns the unquantized value of a color that's represented only as
// a set of bits.
static inline int unquantize_bits_color(int val, int nBits) {
return replicate_bits(val, nBits, 8);
}
// Returns the unquantized value of a color that's represented as a
// trit followed by nBits bits. This algorithm follows the sequence
// defined in section C.2.13 of the ASTC spec.
static inline int unquantize_trit_color(int val, int nBits) {
SkASSERT(nBits > 0);
SkASSERT(nBits < 7);
const int D = (val >> nBits) & 0x3;
SkASSERT(D < 3);
const int A = -(val & 0x1) & 0x1FF;
static const int Cvals[6] = { 204, 93, 44, 22, 11, 5 };
const int C = Cvals[nBits - 1];
int B = 0;
const SkTBits<int> valBits(val);
switch (nBits) {
case 1:
B = 0;
break;
case 2: {
const int b = valBits[1];
B = (b << 1) | (b << 2) | (b << 4) | (b << 8);
}
break;
case 3: {
const int cb = valBits(2, 1);
B = cb | (cb << 2) | (cb << 7);
}
break;
case 4: {
const int dcb = valBits(3, 1);
B = dcb | (dcb << 6);
}
break;
case 5: {
const int edcb = valBits(4, 1);
B = (edcb << 5) | (edcb >> 2);
}
break;
case 6: {
const int fedcb = valBits(5, 1);
B = (fedcb << 4) | (fedcb >> 4);
}
break;
}
return unquantize_value(0x80, A, B, C, D);
}
// Returns the unquantized value of a color that's represented as a
// quint followed by nBits bits. This algorithm follows the sequence
// defined in section C.2.13 of the ASTC spec.
static inline int unquantize_quint_color(int val, int nBits) {
const int D = (val >> nBits) & 0x7;
SkASSERT(D < 5);
const int A = -(val & 0x1) & 0x1FF;
static const int Cvals[5] = { 113, 54, 26, 13, 6 };
SkASSERT(nBits > 0);
SkASSERT(nBits < 6);
const int C = Cvals[nBits - 1];
int B = 0;
const SkTBits<int> valBits(val);
switch (nBits) {
case 1:
B = 0;
break;
case 2: {
const int b = valBits[1];
B = (b << 2) | (b << 3) | (b << 8);
}
break;
case 3: {
const int cb = valBits(2, 1);
B = (cb >> 1) | (cb << 1) | (cb << 7);
}
break;
case 4: {
const int dcb = valBits(3, 1);
B = (dcb >> 1) | (dcb << 6);
}
break;
case 5: {
const int edcb = valBits(4, 1);
B = (edcb << 5) | (edcb >> 3);
}
break;
}
return unquantize_value(0x80, A, B, C, D);
}
// This algorithm takes a list of integers, stored in vals, and unquantizes them
// in place. This follows the algorithm laid out in section C.2.13 of the ASTC spec.
static void unquantize_colors(int *vals, int nVals, int nBits, int nTrits, int nQuints) {
for (int i = 0; i < nVals; ++i) {
if (nTrits > 0) {
SkASSERT(nQuints == 0);
vals[i] = unquantize_trit_color(vals[i], nBits);
} else if (nQuints > 0) {
SkASSERT(nTrits == 0);
vals[i] = unquantize_quint_color(vals[i], nBits);
} else {
SkASSERT(nQuints == 0 && nTrits == 0);
vals[i] = unquantize_bits_color(vals[i], nBits);
}
}
}
// Returns an interpolated value between c0 and c1 based on the weight. This
// follows the algorithm laid out in section C.2.19 of the ASTC spec.
static int interpolate_channel(int c0, int c1, int weight) {
SkASSERT(0 <= c0 && c0 < 256);
SkASSERT(0 <= c1 && c1 < 256);
c0 = (c0 << 8) | c0;
c1 = (c1 << 8) | c1;
const int result = ((c0*(64 - weight) + c1*weight + 32) / 64) >> 8;
if (result > 255) {
return 255;
}
SkASSERT(result >= 0);
return result;
}
// Returns an interpolated color between the two endpoints based on the weight.
static SkColor interpolate_endpoints(const SkColor endpoints[2], int weight) {
return SkColorSetARGB(
interpolate_channel(SkColorGetA(endpoints[0]), SkColorGetA(endpoints[1]), weight),
interpolate_channel(SkColorGetR(endpoints[0]), SkColorGetR(endpoints[1]), weight),
interpolate_channel(SkColorGetG(endpoints[0]), SkColorGetG(endpoints[1]), weight),
interpolate_channel(SkColorGetB(endpoints[0]), SkColorGetB(endpoints[1]), weight));
}
// Returns an interpolated color between the two endpoints based on the weight.
// It uses separate weights for the channel depending on the value of the 'plane'
// variable. By default, all channels will use weight 0, and the value of plane
// means that weight1 will be used for:
// 0: red
// 1: green
// 2: blue
// 3: alpha
static SkColor interpolate_dual_endpoints(
const SkColor endpoints[2], int weight0, int weight1, int plane) {
int a = interpolate_channel(SkColorGetA(endpoints[0]), SkColorGetA(endpoints[1]), weight0);
int r = interpolate_channel(SkColorGetR(endpoints[0]), SkColorGetR(endpoints[1]), weight0);
int g = interpolate_channel(SkColorGetG(endpoints[0]), SkColorGetG(endpoints[1]), weight0);
int b = interpolate_channel(SkColorGetB(endpoints[0]), SkColorGetB(endpoints[1]), weight0);
switch (plane) {
case 0:
r = interpolate_channel(
SkColorGetR(endpoints[0]), SkColorGetR(endpoints[1]), weight1);
break;
case 1:
g = interpolate_channel(
SkColorGetG(endpoints[0]), SkColorGetG(endpoints[1]), weight1);
break;
case 2:
b = interpolate_channel(
SkColorGetB(endpoints[0]), SkColorGetB(endpoints[1]), weight1);
break;
case 3:
a = interpolate_channel(
SkColorGetA(endpoints[0]), SkColorGetA(endpoints[1]), weight1);
break;
default:
SkDEBUGFAIL("Plane should be 0-3");
break;
}
return SkColorSetARGB(a, r, g, b);
}
// A struct of decoded values that we use to carry around information
// about the block. dimX and dimY are the dimension in texels of the block,
// for which there is only a limited subset of valid values:
//
// 4x4, 5x4, 5x5, 6x5, 6x6, 8x5, 8x6, 8x8, 10x5, 10x6, 10x8, 10x10, 12x10, 12x12
struct ASTCDecompressionData {
ASTCDecompressionData(int dimX, int dimY) : fDimX(dimX), fDimY(dimY) { }
const int fDimX; // the X dimension of the decompressed block
const int fDimY; // the Y dimension of the decompressed block
ASTCBlock fBlock; // the block data
int fBlockMode; // the block header that contains the block mode.
bool fDualPlaneEnabled; // is this block compressing dual weight planes?
int fDualPlane; // the independent plane in dual plane mode.
bool fVoidExtent; // is this block a single color?
bool fError; // does this block have an error encoding?
int fWeightDimX; // the x dimension of the weight grid
int fWeightDimY; // the y dimension of the weight grid
int fWeightBits; // the number of bits used for each weight value
int fWeightTrits; // the number of trits used for each weight value
int fWeightQuints; // the number of quints used for each weight value
int fPartCount; // the number of partitions in this block
int fPartIndex; // the partition index: only relevant if fPartCount > 0
// CEM values can be anything in the range 0-15, and each corresponds to a different
// mode that represents the color data. We only support LDR modes.
enum ColorEndpointMode {
kLDR_Luminance_Direct_ColorEndpointMode = 0,
kLDR_Luminance_BaseOffset_ColorEndpointMode = 1,
kHDR_Luminance_LargeRange_ColorEndpointMode = 2,
kHDR_Luminance_SmallRange_ColorEndpointMode = 3,
kLDR_LuminanceAlpha_Direct_ColorEndpointMode = 4,
kLDR_LuminanceAlpha_BaseOffset_ColorEndpointMode = 5,
kLDR_RGB_BaseScale_ColorEndpointMode = 6,
kHDR_RGB_BaseScale_ColorEndpointMode = 7,
kLDR_RGB_Direct_ColorEndpointMode = 8,
kLDR_RGB_BaseOffset_ColorEndpointMode = 9,
kLDR_RGB_BaseScaleWithAlpha_ColorEndpointMode = 10,
kHDR_RGB_ColorEndpointMode = 11,
kLDR_RGBA_Direct_ColorEndpointMode = 12,
kLDR_RGBA_BaseOffset_ColorEndpointMode = 13,
kHDR_RGB_LDRAlpha_ColorEndpointMode = 14,
kHDR_RGB_HDRAlpha_ColorEndpointMode = 15
};
static const int kMaxColorEndpointModes = 16;
// the color endpoint modes for this block.
static const int kMaxPartitions = 4;
ColorEndpointMode fCEM[kMaxPartitions];
int fColorStartBit; // The bit position of the first bit of the color data
int fColorEndBit; // The bit position of the last *possible* bit of the color data
// Returns the number of partitions for this block.
int numPartitions() const {
return fPartCount;
}
// Returns the total number of weight values that are stored in this block
int numWeights() const {
return fWeightDimX * fWeightDimY * (fDualPlaneEnabled ? 2 : 1);
}
#ifdef SK_DEBUG
// Returns the maximum value that any weight can take. We really only use
// this function for debugging.
int maxWeightValue() const {
int maxVal = (1 << fWeightBits);
if (fWeightTrits > 0) {
SkASSERT(0 == fWeightQuints);
maxVal *= 3;
} else if (fWeightQuints > 0) {
SkASSERT(0 == fWeightTrits);
maxVal *= 5;
}
return maxVal - 1;
}
#endif
// The number of bits needed to represent the texel weight data. This
// comes from the 'data size determination' section of the ASTC spec (C.2.22)
int numWeightBits() const {
const int nWeights = this->numWeights();
return
((nWeights*8*fWeightTrits + 4) / 5) +
((nWeights*7*fWeightQuints + 2) / 3) +
(nWeights*fWeightBits);
}
// Returns the number of color values stored in this block. The number of
// values stored is directly a function of the color endpoint modes.
int numColorValues() const {
int numValues = 0;
for (int i = 0; i < this->numPartitions(); ++i) {
int cemInt = static_cast<int>(fCEM[i]);
numValues += ((cemInt >> 2) + 1) * 2;
}
return numValues;
}
// Figures out the number of bits available for color values, and fills
// in the maximum encoding that will fit the number of color values that
// we need. Returns false on error. (See section C.2.22 of the spec)
bool getColorValueEncoding(int *nBits, int *nTrits, int *nQuints) const {
if (NULL == nBits || NULL == nTrits || NULL == nQuints) {
return false;
}
const int nColorVals = this->numColorValues();
if (nColorVals <= 0) {
return false;
}
const int colorBits = fColorEndBit - fColorStartBit;
SkASSERT(colorBits > 0);
// This is the minimum amount of accuracy required by the spec.
if (colorBits < ((13 * nColorVals + 4) / 5)) {
return false;
}
// Values can be represented as at most 8-bit values.
// !SPEED! place this in a lookup table based on colorBits and nColorVals
for (int i = 255; i > 0; --i) {
int range = i + 1;
int bits = 0, trits = 0, quints = 0;
bool valid = false;
if (SkIsPow2(range)) {
bits = bits_for_range(range);
valid = true;
} else if ((range % 3) == 0 && SkIsPow2(range/3)) {
trits = 1;
bits = bits_for_range(range/3);
valid = true;
} else if ((range % 5) == 0 && SkIsPow2(range/5)) {
quints = 1;
bits = bits_for_range(range/5);
valid = true;
}
if (valid) {
const int actualColorBits =
((nColorVals*8*trits + 4) / 5) +
((nColorVals*7*quints + 2) / 3) +
(nColorVals*bits);
if (actualColorBits <= colorBits) {
*nTrits = trits;
*nQuints = quints;
*nBits = bits;
return true;
}
}
}
return false;
}
// Converts the sequence of color values into endpoints. The algorithm here
// corresponds to the values determined by section C.2.14 of the ASTC spec
void colorEndpoints(SkColor endpoints[4][2], const int* colorValues) const {
for (int i = 0; i < this->numPartitions(); ++i) {
switch (fCEM[i]) {
case kLDR_Luminance_Direct_ColorEndpointMode: {
const int* v = colorValues;
endpoints[i][0] = SkColorSetARGB(0xFF, v[0], v[0], v[0]);
endpoints[i][1] = SkColorSetARGB(0xFF, v[1], v[1], v[1]);
colorValues += 2;
}
break;
case kLDR_Luminance_BaseOffset_ColorEndpointMode: {
const int* v = colorValues;
const int L0 = (v[0] >> 2) | (v[1] & 0xC0);
const int L1 = clamp_byte(L0 + (v[1] & 0x3F));
endpoints[i][0] = SkColorSetARGB(0xFF, L0, L0, L0);
endpoints[i][1] = SkColorSetARGB(0xFF, L1, L1, L1);
colorValues += 2;
}
break;
case kLDR_LuminanceAlpha_Direct_ColorEndpointMode: {
const int* v = colorValues;
endpoints[i][0] = SkColorSetARGB(v[2], v[0], v[0], v[0]);
endpoints[i][1] = SkColorSetARGB(v[3], v[1], v[1], v[1]);
colorValues += 4;
}
break;
case kLDR_LuminanceAlpha_BaseOffset_ColorEndpointMode: {
int v0 = colorValues[0];
int v1 = colorValues[1];
int v2 = colorValues[2];
int v3 = colorValues[3];
bit_transfer_signed(&v1, &v0);
bit_transfer_signed(&v3, &v2);
endpoints[i][0] = SkColorSetARGB(v2, v0, v0, v0);
endpoints[i][1] = SkColorSetARGB(
clamp_byte(v3+v2),
clamp_byte(v1+v0),
clamp_byte(v1+v0),
clamp_byte(v1+v0));
colorValues += 4;
}
break;
case kLDR_RGB_BaseScale_ColorEndpointMode: {
decode_rgba_basescale(colorValues, endpoints[i], true);
colorValues += 4;
}
break;
case kLDR_RGB_Direct_ColorEndpointMode: {
decode_rgba_direct(colorValues, endpoints[i], true);
colorValues += 6;
}
break;
case kLDR_RGB_BaseOffset_ColorEndpointMode: {
decode_rgba_baseoffset(colorValues, endpoints[i], true);
colorValues += 6;
}
break;
case kLDR_RGB_BaseScaleWithAlpha_ColorEndpointMode: {
decode_rgba_basescale(colorValues, endpoints[i], false);
colorValues += 6;
}
break;
case kLDR_RGBA_Direct_ColorEndpointMode: {
decode_rgba_direct(colorValues, endpoints[i], false);
colorValues += 8;
}
break;
case kLDR_RGBA_BaseOffset_ColorEndpointMode: {
decode_rgba_baseoffset(colorValues, endpoints[i], false);
colorValues += 8;
}
break;
default:
SkDEBUGFAIL("HDR mode unsupported! This should be caught sooner.");
break;
}
}
}
// Follows the procedure from section C.2.17 of the ASTC specification
int unquantizeWeight(int x) const {
SkASSERT(x <= this->maxWeightValue());
const int D = (x >> fWeightBits) & 0x7;
const int A = -(x & 0x1) & 0x7F;
SkTBits<int> xbits(x);
int T = 0;
if (fWeightTrits > 0) {
SkASSERT(0 == fWeightQuints);
switch (fWeightBits) {
case 0: {
// x is a single trit
SkASSERT(x < 3);
static const int kUnquantizationTable[3] = { 0, 32, 63 };
T = kUnquantizationTable[x];
}
break;
case 1: {
const int B = 0;
const int C = 50;
T = unquantize_value(0x20, A, B, C, D);
}
break;
case 2: {
const int b = xbits[1];
const int B = b | (b << 2) | (b << 6);
const int C = 23;
T = unquantize_value(0x20, A, B, C, D);
}
break;
case 3: {
const int cb = xbits(2, 1);
const int B = cb | (cb << 5);
const int C = 11;
T = unquantize_value(0x20, A, B, C, D);
}
break;
default:
SkDEBUGFAIL("Too many bits for trit encoding");
break;
}
} else if (fWeightQuints > 0) {
SkASSERT(0 == fWeightTrits);
switch (fWeightBits) {
case 0: {
// x is a single quint
SkASSERT(x < 5);
static const int kUnquantizationTable[5] = { 0, 16, 32, 47, 63 };
T = kUnquantizationTable[x];
}
break;
case 1: {
const int B = 0;
const int C = 28;
T = unquantize_value(0x20, A, B, C, D);
}
break;
case 2: {
const int b = xbits[1];
const int B = (b << 1) | (b << 6);
const int C = 13;
T = unquantize_value(0x20, A, B, C, D);
}
break;
default:
SkDEBUGFAIL("Too many bits for quint encoding");
break;
}
} else {
SkASSERT(0 == fWeightTrits);
SkASSERT(0 == fWeightQuints);
T = replicate_bits(x, fWeightBits, 6);
}
// This should bring the value within [0, 63]..
SkASSERT(T <= 63);
if (T > 32) {
T += 1;
}
SkASSERT(T <= 64);
return T;
}
// Returns the weight at the associated index. If the index is out of bounds, it
// returns zero. It also chooses the weight appropriately based on the given dual
// plane.
int getWeight(const int* unquantizedWeights, int idx, bool dualPlane) const {
const int maxIdx = (fDualPlaneEnabled ? 2 : 1) * fWeightDimX * fWeightDimY - 1;
if (fDualPlaneEnabled) {
const int effectiveIdx = 2*idx + (dualPlane ? 1 : 0);
if (effectiveIdx > maxIdx) {
return 0;
}
return unquantizedWeights[effectiveIdx];
}
SkASSERT(!dualPlane);
if (idx > maxIdx) {
return 0;
} else {
return unquantizedWeights[idx];
}
}
// This computes the effective weight at location (s, t) of the block. This
// weight is computed by sampling the texel weight grid (it's usually not 1-1), and
// then applying a bilerp. The algorithm outlined here follows the algorithm
// defined in section C.2.18 of the ASTC spec.
int infillWeight(const int* unquantizedValues, int s, int t, bool dualPlane) const {
const int Ds = (1024 + fDimX/2) / (fDimX - 1);
const int Dt = (1024 + fDimY/2) / (fDimY - 1);
const int cs = Ds * s;
const int ct = Dt * t;
const int gs = (cs*(fWeightDimX - 1) + 32) >> 6;
const int gt = (ct*(fWeightDimY - 1) + 32) >> 6;
const int js = gs >> 4;
const int jt = gt >> 4;
const int fs = gs & 0xF;
const int ft = gt & 0xF;
const int idx = js + jt*fWeightDimX;
const int p00 = this->getWeight(unquantizedValues, idx, dualPlane);
const int p01 = this->getWeight(unquantizedValues, idx + 1, dualPlane);
const int p10 = this->getWeight(unquantizedValues, idx + fWeightDimX, dualPlane);
const int p11 = this->getWeight(unquantizedValues, idx + fWeightDimX + 1, dualPlane);
const int w11 = (fs*ft + 8) >> 4;
const int w10 = ft - w11;
const int w01 = fs - w11;
const int w00 = 16 - fs - ft + w11;
const int weight = (p00*w00 + p01*w01 + p10*w10 + p11*w11 + 8) >> 4;
SkASSERT(weight <= 64);
return weight;
}
// Unquantizes the decoded texel weights as described in section C.2.17 of
// the ASTC specification. Additionally, it populates texelWeights with
// the expanded weight grid, which is computed according to section C.2.18
void texelWeights(int texelWeights[2][12][12], const int* texelValues) const {
// Unquantized texel weights...
int unquantizedValues[144*2]; // 12x12 blocks with dual plane decoding...
SkASSERT(this->numWeights() <= 144*2);
// Unquantize the weights and cache them
for (int j = 0; j < this->numWeights(); ++j) {
unquantizedValues[j] = this->unquantizeWeight(texelValues[j]);
}
// Do weight infill...
for (int y = 0; y < fDimY; ++y) {
for (int x = 0; x < fDimX; ++x) {
texelWeights[0][x][y] = this->infillWeight(unquantizedValues, x, y, false);
if (fDualPlaneEnabled) {
texelWeights[1][x][y] = this->infillWeight(unquantizedValues, x, y, true);
}
}
}
}
// Returns the partition for the texel located at position (x, y).
// Adapted from C.2.21 of the ASTC specification
int getPartition(int x, int y) const {
const int partitionCount = this->numPartitions();
int seed = fPartIndex;
if ((fDimX * fDimY) < 31) {
x <<= 1;
y <<= 1;
}
seed += (partitionCount - 1) * 1024;
uint32_t p = seed;
p ^= p >> 15; p -= p << 17; p += p << 7; p += p << 4;
p ^= p >> 5; p += p << 16; p ^= p >> 7; p ^= p >> 3;
p ^= p << 6; p ^= p >> 17;
uint32_t rnum = p;
uint8_t seed1 = rnum & 0xF;
uint8_t seed2 = (rnum >> 4) & 0xF;
uint8_t seed3 = (rnum >> 8) & 0xF;
uint8_t seed4 = (rnum >> 12) & 0xF;
uint8_t seed5 = (rnum >> 16) & 0xF;
uint8_t seed6 = (rnum >> 20) & 0xF;
uint8_t seed7 = (rnum >> 24) & 0xF;
uint8_t seed8 = (rnum >> 28) & 0xF;
uint8_t seed9 = (rnum >> 18) & 0xF;
uint8_t seed10 = (rnum >> 22) & 0xF;
uint8_t seed11 = (rnum >> 26) & 0xF;
uint8_t seed12 = ((rnum >> 30) | (rnum << 2)) & 0xF;
seed1 *= seed1; seed2 *= seed2;
seed3 *= seed3; seed4 *= seed4;
seed5 *= seed5; seed6 *= seed6;
seed7 *= seed7; seed8 *= seed8;
seed9 *= seed9; seed10 *= seed10;
seed11 *= seed11; seed12 *= seed12;
int sh1, sh2, sh3;
if (0 != (seed & 1)) {
sh1 = (0 != (seed & 2))? 4 : 5;
sh2 = (partitionCount == 3)? 6 : 5;
} else {
sh1 = (partitionCount==3)? 6 : 5;
sh2 = (0 != (seed & 2))? 4 : 5;
}
sh3 = (0 != (seed & 0x10))? sh1 : sh2;
seed1 >>= sh1; seed2 >>= sh2; seed3 >>= sh1; seed4 >>= sh2;
seed5 >>= sh1; seed6 >>= sh2; seed7 >>= sh1; seed8 >>= sh2;
seed9 >>= sh3; seed10 >>= sh3; seed11 >>= sh3; seed12 >>= sh3;
const int z = 0;
int a = seed1*x + seed2*y + seed11*z + (rnum >> 14);
int b = seed3*x + seed4*y + seed12*z + (rnum >> 10);
int c = seed5*x + seed6*y + seed9 *z + (rnum >> 6);
int d = seed7*x + seed8*y + seed10*z + (rnum >> 2);
a &= 0x3F;
b &= 0x3F;
c &= 0x3F;
d &= 0x3F;
if (partitionCount < 4) {
d = 0;
}
if (partitionCount < 3) {
c = 0;
}
if (a >= b && a >= c && a >= d) {
return 0;
} else if (b >= c && b >= d) {
return 1;
} else if (c >= d) {
return 2;
} else {
return 3;
}
}
// Performs the proper interpolation of the texel based on the
// endpoints and weights.
SkColor getTexel(const SkColor endpoints[4][2],
const int weights[2][12][12],
int x, int y) const {
int part = 0;
if (this->numPartitions() > 1) {
part = this->getPartition(x, y);
}
SkColor result;
if (fDualPlaneEnabled) {
result = interpolate_dual_endpoints(
endpoints[part], weights[0][x][y], weights[1][x][y], fDualPlane);
} else {
result = interpolate_endpoints(endpoints[part], weights[0][x][y]);
}
#if 1
// !FIXME! if we're writing directly to a bitmap, then we don't need
// to swap the red and blue channels, but since we're usually being used
// by the SkImageDecoder_astc module, the results are expected to be in RGBA.
result = SkColorSetARGB(
SkColorGetA(result), SkColorGetB(result), SkColorGetG(result), SkColorGetR(result));
#endif
return result;
}
void decode() {
// First decode the block mode.
this->decodeBlockMode();
// Now we can decode the partition information.
fPartIndex = static_cast<int>(read_astc_bits(fBlock, 11, 23));
fPartCount = (fPartIndex & 0x3) + 1;
fPartIndex >>= 2;
// This is illegal
if (fDualPlaneEnabled && this->numPartitions() == 4) {
fError = true;
return;
}
// Based on the partition info, we can decode the color information.
this->decodeColorData();
}
// Decodes the dual plane based on the given bit location. The final
// location, if the dual plane is enabled, is also the end of our color data.
// This function is only meant to be used from this->decodeColorData()
void decodeDualPlane(int bitLoc) {
if (fDualPlaneEnabled) {
fDualPlane = static_cast<int>(read_astc_bits(fBlock, bitLoc - 2, bitLoc));
fColorEndBit = bitLoc - 2;
} else {
fColorEndBit = bitLoc;
}
}
// Decodes the color information based on the ASTC spec.
void decodeColorData() {
// By default, the last color bit is at the end of the texel weights
const int lastWeight = 128 - this->numWeightBits();
// If we have a dual plane then it will be at this location, too.
int dualPlaneBitLoc = lastWeight;
// If there's only one partition, then our job is (relatively) easy.
if (this->numPartitions() == 1) {
fCEM[0] = static_cast<ColorEndpointMode>(read_astc_bits(fBlock, 13, 17));
fColorStartBit = 17;
// Handle dual plane mode...
this->decodeDualPlane(dualPlaneBitLoc);
return;
}
// If we have more than one partition, then we need to make
// room for the partition index.
fColorStartBit = 29;
// Read the base CEM. If it's zero, then we have no additional
// CEM data and the endpoints for each partition share the same CEM.
const int baseCEM = static_cast<int>(read_astc_bits(fBlock, 23, 25));
if (0 == baseCEM) {
const ColorEndpointMode sameCEM =
static_cast<ColorEndpointMode>(read_astc_bits(fBlock, 25, 29));
for (int i = 0; i < kMaxPartitions; ++i) {
fCEM[i] = sameCEM;
}
// Handle dual plane mode...
this->decodeDualPlane(dualPlaneBitLoc);
return;
}
// Move the dual plane selector bits down based on how many
// partitions the block contains.
switch (this->numPartitions()) {
case 2:
dualPlaneBitLoc -= 2;
break;
case 3:
dualPlaneBitLoc -= 5;
break;
case 4:
dualPlaneBitLoc -= 8;
break;
default:
SkDEBUGFAIL("Internal ASTC decoding error.");
break;
}
// The rest of the CEM config will be between the dual plane bit selector
// and the texel weight grid.
const int lowCEM = static_cast<int>(read_astc_bits(fBlock, 23, 29));
SkASSERT(lastWeight >= dualPlaneBitLoc);
SkASSERT(lastWeight - dualPlaneBitLoc < 31);
int fullCEM = static_cast<int>(read_astc_bits(fBlock, dualPlaneBitLoc, lastWeight));
// Attach the config at the end of the weight grid to the CEM values
// in the beginning of the block.
fullCEM = (fullCEM << 6) | lowCEM;
// Ignore the two least significant bits, since those are our baseCEM above.
fullCEM = fullCEM >> 2;
int C[kMaxPartitions]; // Next, decode C and M from the spec (Table C.2.12)
for (int i = 0; i < this->numPartitions(); ++i) {
C[i] = fullCEM & 1;
fullCEM = fullCEM >> 1;
}
int M[kMaxPartitions];
for (int i = 0; i < this->numPartitions(); ++i) {
M[i] = fullCEM & 0x3;
fullCEM = fullCEM >> 2;
}
// Construct our CEMs..
SkASSERT(baseCEM > 0);
for (int i = 0; i < this->numPartitions(); ++i) {
int cem = (baseCEM - 1) * 4;
cem += (0 == C[i])? 0 : 4;
cem += M[i];
SkASSERT(cem < 16);
fCEM[i] = static_cast<ColorEndpointMode>(cem);
}
// Finally, if we have dual plane mode, then read the plane selector.
this->decodeDualPlane(dualPlaneBitLoc);
}
// Decodes the block mode. This function determines whether or not we use
// dual plane encoding, the size of the texel weight grid, and the number of
// bits, trits and quints that are used to encode it. For more information,
// see section C.2.10 of the ASTC spec.
//
// For 2D blocks, the Block Mode field is laid out as follows:
//
// -------------------------------------------------------------------------
// 10 9 8 7 6 5 4 3 2 1 0 Width Height Notes
// -------------------------------------------------------------------------
// D H B A R0 0 0 R2 R1 B+4 A+2
// D H B A R0 0 1 R2 R1 B+8 A+2
// D H B A R0 1 0 R2 R1 A+2 B+8
// D H 0 B A R0 1 1 R2 R1 A+2 B+6
// D H 1 B A R0 1 1 R2 R1 B+2 A+2
// D H 0 0 A R0 R2 R1 0 0 12 A+2
// D H 0 1 A R0 R2 R1 0 0 A+2 12
// D H 1 1 0 0 R0 R2 R1 0 0 6 10
// D H 1 1 0 1 R0 R2 R1 0 0 10 6
// B 1 0 A R0 R2 R1 0 0 A+6 B+6 D=0, H=0
// x x 1 1 1 1 1 1 1 0 0 - - Void-extent
// x x 1 1 1 x x x x 0 0 - - Reserved*
// x x x x x x x 0 0 0 0 - - Reserved
// -------------------------------------------------------------------------
//
// D - dual plane enabled
// H, R - used to determine the number of bits/trits/quints in texel weight encoding
// R is a three bit value whose LSB is R0 and MSB is R1
// Width, Height - dimensions of the texel weight grid (determined by A and B)
void decodeBlockMode() {
const int blockMode = static_cast<int>(read_astc_bits(fBlock, 0, 11));
// Check for special void extent encoding
fVoidExtent = (blockMode & 0x1FF) == 0x1FC;
// Check for reserved block modes
fError = ((blockMode & 0x1C3) == 0x1C0) || ((blockMode & 0xF) == 0);
// Neither reserved nor void-extent, decode as usual
// This code corresponds to table C.2.8 of the ASTC spec
bool highPrecision = false;
int R = 0;
if ((blockMode & 0x3) == 0) {
R = ((0xC & blockMode) >> 1) | ((0x10 & blockMode) >> 4);
const int bitsSevenAndEight = (blockMode & 0x180) >> 7;
SkASSERT(0 <= bitsSevenAndEight && bitsSevenAndEight < 4);
const int A = (blockMode >> 5) & 0x3;
const int B = (blockMode >> 9) & 0x3;
fDualPlaneEnabled = (blockMode >> 10) & 0x1;
highPrecision = (blockMode >> 9) & 0x1;
switch (bitsSevenAndEight) {
default:
case 0:
fWeightDimX = 12;
fWeightDimY = A + 2;
break;
case 1:
fWeightDimX = A + 2;
fWeightDimY = 12;
break;
case 2:
fWeightDimX = A + 6;
fWeightDimY = B + 6;
fDualPlaneEnabled = false;
highPrecision = false;
break;
case 3:
if (0 == A) {
fWeightDimX = 6;
fWeightDimY = 10;
} else {
fWeightDimX = 10;
fWeightDimY = 6;
}
break;
}
} else { // (blockMode & 0x3) != 0
R = ((blockMode & 0x3) << 1) | ((blockMode & 0x10) >> 4);
const int bitsTwoAndThree = (blockMode >> 2) & 0x3;
SkASSERT(0 <= bitsTwoAndThree && bitsTwoAndThree < 4);
const int A = (blockMode >> 5) & 0x3;
const int B = (blockMode >> 7) & 0x3;
fDualPlaneEnabled = (blockMode >> 10) & 0x1;
highPrecision = (blockMode >> 9) & 0x1;
switch (bitsTwoAndThree) {
case 0:
fWeightDimX = B + 4;
fWeightDimY = A + 2;
break;
case 1:
fWeightDimX = B + 8;
fWeightDimY = A + 2;
break;
case 2:
fWeightDimX = A + 2;
fWeightDimY = B + 8;
break;
case 3:
if ((B & 0x2) == 0) {
fWeightDimX = A + 2;
fWeightDimY = (B & 1) + 6;
} else {
fWeightDimX = (B & 1) + 2;
fWeightDimY = A + 2;
}
break;
}
}
// We should have set the values of R and highPrecision
// from decoding the block mode, these are used to determine
// the proper dimensions of our weight grid.
if ((R & 0x6) == 0) {
fError = true;
} else {
static const int kBitAllocationTable[2][6][3] = {
{
{ 1, 0, 0 },
{ 0, 1, 0 },
{ 2, 0, 0 },
{ 0, 0, 1 },
{ 1, 1, 0 },
{ 3, 0, 0 }
},
{
{ 1, 0, 1 },
{ 2, 1, 0 },
{ 4, 0, 0 },
{ 2, 0, 1 },
{ 3, 1, 0 },
{ 5, 0, 0 }
}
};
fWeightBits = kBitAllocationTable[highPrecision][R - 2][0];
fWeightTrits = kBitAllocationTable[highPrecision][R - 2][1];
fWeightQuints = kBitAllocationTable[highPrecision][R - 2][2];
}
}
};
// Reads an ASTC block from the given pointer.
static inline void read_astc_block(ASTCDecompressionData *dst, const uint8_t* src) {
const uint64_t* qword = reinterpret_cast<const uint64_t*>(src);
dst->fBlock.fLow = SkEndian_SwapLE64(qword[0]);
dst->fBlock.fHigh = SkEndian_SwapLE64(qword[1]);
dst->decode();
}
// Take a known void-extent block, and write out the values as a constant color.
static void decompress_void_extent(uint8_t* dst, int dstRowBytes,
const ASTCDecompressionData &data) {
// The top 64 bits contain 4 16-bit RGBA values.
int a = (static_cast<int>(read_astc_bits(data.fBlock, 112, 128)) + 255) >> 8;
int b = (static_cast<int>(read_astc_bits(data.fBlock, 96, 112)) + 255) >> 8;
int g = (static_cast<int>(read_astc_bits(data.fBlock, 80, 96)) + 255) >> 8;
int r = (static_cast<int>(read_astc_bits(data.fBlock, 64, 80)) + 255) >> 8;
write_constant_color(dst, data.fDimX, data.fDimY, dstRowBytes, SkColorSetARGB(a, r, g, b));
}
// Decompresses a single ASTC block. It's assumed that data.fDimX and data.fDimY are
// set and that the block has already been decoded (i.e. data.decode() has been called)
static void decompress_astc_block(uint8_t* dst, int dstRowBytes,
const ASTCDecompressionData &data) {
if (data.fError) {
write_error_color(dst, data.fDimX, data.fDimY, dstRowBytes);
return;
}
if (data.fVoidExtent) {
decompress_void_extent(dst, dstRowBytes, data);
return;
}
// According to the spec, any more than 64 values is illegal. (C.2.24)
static const int kMaxTexelValues = 64;
// Decode the texel weights.
int texelValues[kMaxTexelValues];
bool success = decode_integer_sequence(
texelValues, kMaxTexelValues, data.numWeights(),
// texel data goes to the end of the 128 bit block.
data.fBlock, 128, 128 - data.numWeightBits(), false,
data.fWeightBits, data.fWeightTrits, data.fWeightQuints);
if (!success) {
write_error_color(dst, data.fDimX, data.fDimY, dstRowBytes);
return;
}
// Decode the color endpoints
int colorBits, colorTrits, colorQuints;
if (!data.getColorValueEncoding(&colorBits, &colorTrits, &colorQuints)) {
write_error_color(dst, data.fDimX, data.fDimY, dstRowBytes);
return;
}
// According to the spec, any more than 18 color values is illegal. (C.2.24)
static const int kMaxColorValues = 18;
int colorValues[kMaxColorValues];
success = decode_integer_sequence(
colorValues, kMaxColorValues, data.numColorValues(),
data.fBlock, data.fColorStartBit, data.fColorEndBit, true,
colorBits, colorTrits, colorQuints);
if (!success) {
write_error_color(dst, data.fDimX, data.fDimY, dstRowBytes);
return;
}
// Unquantize the color values after they've been decoded.
unquantize_colors(colorValues, data.numColorValues(), colorBits, colorTrits, colorQuints);
// Decode the colors into the appropriate endpoints.
SkColor endpoints[4][2];
data.colorEndpoints(endpoints, colorValues);
// Do texel infill and decode the texel values.
int texelWeights[2][12][12];
data.texelWeights(texelWeights, texelValues);
// Write the texels by interpolating them based on the information
// stored in the block.
dst += data.fDimY * dstRowBytes;
for (int y = 0; y < data.fDimY; ++y) {
dst -= dstRowBytes;
SkColor* colorPtr = reinterpret_cast<SkColor*>(dst);
for (int x = 0; x < data.fDimX; ++x) {
colorPtr[x] = data.getTexel(endpoints, texelWeights, x, y);
}
}
}
////////////////////////////////////////////////////////////////////////////////
//
// ASTC Comrpession Struct
//
////////////////////////////////////////////////////////////////////////////////
// This is the type passed as the CompressorType argument of the compressed
// blitter for the ASTC format. The static functions required to be in this
// struct are documented in SkTextureCompressor_Blitter.h
struct CompressorASTC {
static inline void CompressA8Vertical(uint8_t* dst, const uint8_t* src) {
compress_a8_astc_block<GetAlphaTranspose>(&dst, src, 12);
}
static inline void CompressA8Horizontal(uint8_t* dst, const uint8_t* src,
int srcRowBytes) {
compress_a8_astc_block<GetAlpha>(&dst, src, srcRowBytes);
}
#if PEDANTIC_BLIT_RECT
static inline void UpdateBlock(uint8_t* dst, const uint8_t* src, int srcRowBytes,
const uint8_t* mask) {
// TODO: krajcevski
// This is kind of difficult for ASTC because the weight values are calculated
// as an average of the actual weights. The best we can do is decompress the
// weights and recalculate them based on the new texel values. This should
// be "not too bad" since we know that anytime we hit this function, we're
// compressing 12x12 block dimension alpha-only, and we know the layout
// of the block
SkFAIL("Implement me!");
}
#endif
};
////////////////////////////////////////////////////////////////////////////////
namespace SkTextureCompressor {
bool CompressA8To12x12ASTC(uint8_t* dst, const uint8_t* src,
int width, int height, size_t rowBytes) {
if (width < 0 || ((width % 12) != 0) || height < 0 || ((height % 12) != 0)) {
return false;
}
uint8_t** dstPtr = &dst;
for (int y = 0; y < height; y += 12) {
for (int x = 0; x < width; x += 12) {
compress_a8_astc_block<GetAlpha>(dstPtr, src + y*rowBytes + x, rowBytes);
}
}
return true;
}
SkBlitter* CreateASTCBlitter(int width, int height, void* outputBuffer,
SkTBlitterAllocator* allocator) {
if ((width % 12) != 0 || (height % 12) != 0) {
return NULL;
}
// Memset the output buffer to an encoding that decodes to zero. We must do this
// in order to avoid having uninitialized values in the buffer if the blitter
// decides not to write certain scanlines (and skip entire rows of blocks).
// In the case of ASTC, if everything index is zero, then the interpolated value
// will decode to zero provided we have the right header. We use the encoding
// from recognizing all zero blocks from above.
const int nBlocks = (width * height / 144);
uint8_t *dst = reinterpret_cast<uint8_t *>(outputBuffer);
for (int i = 0; i < nBlocks; ++i) {
send_packing(&dst, SkTEndian_SwapLE64(0x0000000001FE000173ULL), 0);
}
return allocator->createT<
SkTCompressedAlphaBlitter<12, 16, CompressorASTC>, int, int, void* >
(width, height, outputBuffer);
}
void DecompressASTC(uint8_t* dst, int dstRowBytes, const uint8_t* src,
int width, int height, int blockDimX, int blockDimY) {
// ASTC is encoded in what they call "raster order", so that the first
// block is the bottom-left block in the image, and the first pixel
// is the bottom-left pixel of the image
dst += height * dstRowBytes;
ASTCDecompressionData data(blockDimX, blockDimY);
for (int y = 0; y < height; y += blockDimY) {
dst -= blockDimY * dstRowBytes;
SkColor *colorPtr = reinterpret_cast<SkColor*>(dst);
for (int x = 0; x < width; x += blockDimX) {
read_astc_block(&data, src);
decompress_astc_block(reinterpret_cast<uint8_t*>(colorPtr + x), dstRowBytes, data);
// ASTC encoded blocks are 16 bytes (128 bits) large.
src += 16;
}
}
}
} // SkTextureCompressor