/*
* Copyright 2006 The Android Open Source Project
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkBlurMask.h"
#include "SkColorPriv.h"
#include "SkMaskBlurFilter.h"
#include "SkMath.h"
#include "SkTemplates.h"
#include "SkEndian.h"
// This constant approximates the scaling done in the software path's
// "high quality" mode, in SkBlurMask::Blur() (1 / sqrt(3)).
// IMHO, it actually should be 1: we blur "less" than we should do
// according to the CSS and canvas specs, simply because Safari does the same.
// Firefox used to do the same too, until 4.0 where they fixed it. So at some
// point we should probably get rid of these scaling constants and rebaseline
// all the blur tests.
static const SkScalar kBLUR_SIGMA_SCALE = 0.57735f;
SkScalar SkBlurMask::ConvertRadiusToSigma(SkScalar radius) {
return radius > 0 ? kBLUR_SIGMA_SCALE * radius + 0.5f : 0.0f;
}
SkScalar SkBlurMask::ConvertSigmaToRadius(SkScalar sigma) {
return sigma > 0.5f ? (sigma - 0.5f) / kBLUR_SIGMA_SCALE : 0.0f;
}
static void merge_src_with_blur(uint8_t dst[], int dstRB,
const uint8_t src[], int srcRB,
const uint8_t blur[], int blurRB,
int sw, int sh) {
dstRB -= sw;
srcRB -= sw;
blurRB -= sw;
while (--sh >= 0) {
for (int x = sw - 1; x >= 0; --x) {
*dst = SkToU8(SkAlphaMul(*blur, SkAlpha255To256(*src)));
dst += 1;
src += 1;
blur += 1;
}
dst += dstRB;
src += srcRB;
blur += blurRB;
}
}
static void clamp_with_orig(uint8_t dst[], int dstRowBytes,
const uint8_t src[], int srcRowBytes,
int sw, int sh,
SkBlurStyle style) {
int x;
while (--sh >= 0) {
switch (style) {
case kSolid_SkBlurStyle:
for (x = sw - 1; x >= 0; --x) {
int s = *src;
int d = *dst;
*dst = SkToU8(s + d - SkMulDiv255Round(s, d));
dst += 1;
src += 1;
}
break;
case kOuter_SkBlurStyle:
for (x = sw - 1; x >= 0; --x) {
if (*src) {
*dst = SkToU8(SkAlphaMul(*dst, SkAlpha255To256(255 - *src)));
}
dst += 1;
src += 1;
}
break;
default:
SkDEBUGFAIL("Unexpected blur style here");
break;
}
dst += dstRowBytes - sw;
src += srcRowBytes - sw;
}
}
///////////////////////////////////////////////////////////////////////////////
// we use a local function to wrap the class static method to work around
// a bug in gcc98
void SkMask_FreeImage(uint8_t* image);
void SkMask_FreeImage(uint8_t* image) {
SkMask::FreeImage(image);
}
bool SkBlurMask::BoxBlur(SkMask* dst, const SkMask& src,
SkScalar sigma, SkBlurStyle style, SkBlurQuality quality,
SkIPoint* margin, bool force_quality) {
if (src.fFormat != SkMask::kA8_Format) {
return false;
}
SkIPoint border;
SkMaskBlurFilter blurFilter{sigma, sigma};
if (blurFilter.hasNoBlur()) {
return false;
}
border = blurFilter.blur(src, dst);
// If src.fImage is null, then this call is only to calculate the border.
if (src.fImage != nullptr && dst->fImage == nullptr) {
return false;
}
if (src.fImage != nullptr) {
// if need be, alloc the "real" dst (same size as src) and copy/merge
// the blur into it (applying the src)
if (style == kInner_SkBlurStyle) {
// now we allocate the "real" dst, mirror the size of src
size_t srcSize = src.computeImageSize();
if (0 == srcSize) {
return false; // too big to allocate, abort
}
auto blur = dst->fImage;
dst->fImage = SkMask::AllocImage(srcSize);
auto blurStart = &blur[border.x() + border.y() * dst->fRowBytes];
merge_src_with_blur(dst->fImage, src.fRowBytes,
src.fImage, src.fRowBytes,
blurStart,
dst->fRowBytes,
src.fBounds.width(), src.fBounds.height());
SkMask::FreeImage(blur);
} else if (style != kNormal_SkBlurStyle) {
auto dstStart = &dst->fImage[border.x() + border.y() * dst->fRowBytes];
clamp_with_orig(dstStart,
dst->fRowBytes, src.fImage, src.fRowBytes,
src.fBounds.width(), src.fBounds.height(), style);
}
}
if (style == kInner_SkBlurStyle) {
dst->fBounds = src.fBounds; // restore trimmed bounds
dst->fRowBytes = src.fRowBytes;
}
if (margin != nullptr) {
*margin = border;
}
return true;
}
/* Convolving a box with itself three times results in a piecewise
quadratic function:
0 x <= -1.5
9/8 + 3/2 x + 1/2 x^2 -1.5 < x <= -.5
3/4 - x^2 -.5 < x <= .5
9/8 - 3/2 x + 1/2 x^2 0.5 < x <= 1.5
0 1.5 < x
Mathematica:
g[x_] := Piecewise [ {
{9/8 + 3/2 x + 1/2 x^2 , -1.5 < x <= -.5},
{3/4 - x^2 , -.5 < x <= .5},
{9/8 - 3/2 x + 1/2 x^2 , 0.5 < x <= 1.5}
}, 0]
To get the profile curve of the blurred step function at the rectangle
edge, we evaluate the indefinite integral, which is piecewise cubic:
0 x <= -1.5
9/16 + 9/8 x + 3/4 x^2 + 1/6 x^3 -1.5 < x <= -0.5
1/2 + 3/4 x - 1/3 x^3 -.5 < x <= .5
7/16 + 9/8 x - 3/4 x^2 + 1/6 x^3 .5 < x <= 1.5
1 1.5 < x
in Mathematica code:
gi[x_] := Piecewise[ {
{ 0 , x <= -1.5 },
{ 9/16 + 9/8 x + 3/4 x^2 + 1/6 x^3, -1.5 < x <= -0.5 },
{ 1/2 + 3/4 x - 1/3 x^3 , -.5 < x <= .5},
{ 7/16 + 9/8 x - 3/4 x^2 + 1/6 x^3, .5 < x <= 1.5}
},1]
*/
static float gaussianIntegral(float x) {
if (x > 1.5f) {
return 0.0f;
}
if (x < -1.5f) {
return 1.0f;
}
float x2 = x*x;
float x3 = x2*x;
if ( x > 0.5f ) {
return 0.5625f - (x3 / 6.0f - 3.0f * x2 * 0.25f + 1.125f * x);
}
if ( x > -0.5f ) {
return 0.5f - (0.75f * x - x3 / 3.0f);
}
return 0.4375f + (-x3 / 6.0f - 3.0f * x2 * 0.25f - 1.125f * x);
}
/* ComputeBlurProfile fills in an array of floating
point values between 0 and 255 for the profile signature of
a blurred half-plane with the given blur radius. Since we're
going to be doing screened multiplications (i.e., 1 - (1-x)(1-y))
all the time, we actually fill in the profile pre-inverted
(already done 255-x).
*/
void SkBlurMask::ComputeBlurProfile(uint8_t* profile, int size, SkScalar sigma) {
SkASSERT(SkScalarCeilToInt(6*sigma) == size);
int center = size >> 1;
float invr = 1.f/(2*sigma);
profile[0] = 255;
for (int x = 1 ; x < size ; ++x) {
float scaled_x = (center - x - .5f) * invr;
float gi = gaussianIntegral(scaled_x);
profile[x] = 255 - (uint8_t) (255.f * gi);
}
}
// TODO MAYBE: Maintain a profile cache to avoid recomputing this for
// commonly used radii. Consider baking some of the most common blur radii
// directly in as static data?
// Implementation adapted from Michael Herf's approach:
// http://stereopsis.com/shadowrect/
uint8_t SkBlurMask::ProfileLookup(const uint8_t *profile, int loc,
int blurredWidth, int sharpWidth) {
// how far are we from the original edge?
int dx = SkAbs32(((loc << 1) + 1) - blurredWidth) - sharpWidth;
int ox = dx >> 1;
if (ox < 0) {
ox = 0;
}
return profile[ox];
}
void SkBlurMask::ComputeBlurredScanline(uint8_t *pixels, const uint8_t *profile,
unsigned int width, SkScalar sigma) {
unsigned int profile_size = SkScalarCeilToInt(6*sigma);
SkAutoTMalloc<uint8_t> horizontalScanline(width);
unsigned int sw = width - profile_size;
// nearest odd number less than the profile size represents the center
// of the (2x scaled) profile
int center = ( profile_size & ~1 ) - 1;
int w = sw - center;
for (unsigned int x = 0 ; x < width ; ++x) {
if (profile_size <= sw) {
pixels[x] = ProfileLookup(profile, x, width, w);
} else {
float span = float(sw)/(2*sigma);
float giX = 1.5f - (x+.5f)/(2*sigma);
pixels[x] = (uint8_t) (255 * (gaussianIntegral(giX) - gaussianIntegral(giX + span)));
}
}
}
bool SkBlurMask::BlurRect(SkScalar sigma, SkMask *dst,
const SkRect &src, SkBlurStyle style,
SkIPoint *margin, SkMask::CreateMode createMode) {
int profileSize = SkScalarCeilToInt(6*sigma);
if (profileSize <= 0) {
return false; // no blur to compute
}
int pad = profileSize/2;
if (margin) {
margin->set( pad, pad );
}
dst->fBounds.set(SkScalarRoundToInt(src.fLeft - pad),
SkScalarRoundToInt(src.fTop - pad),
SkScalarRoundToInt(src.fRight + pad),
SkScalarRoundToInt(src.fBottom + pad));
dst->fRowBytes = dst->fBounds.width();
dst->fFormat = SkMask::kA8_Format;
dst->fImage = nullptr;
int sw = SkScalarFloorToInt(src.width());
int sh = SkScalarFloorToInt(src.height());
if (createMode == SkMask::kJustComputeBounds_CreateMode) {
if (style == kInner_SkBlurStyle) {
dst->fBounds.set(SkScalarRoundToInt(src.fLeft),
SkScalarRoundToInt(src.fTop),
SkScalarRoundToInt(src.fRight),
SkScalarRoundToInt(src.fBottom)); // restore trimmed bounds
dst->fRowBytes = sw;
}
return true;
}
SkAutoTMalloc<uint8_t> profile(profileSize);
ComputeBlurProfile(profile, profileSize, sigma);
size_t dstSize = dst->computeImageSize();
if (0 == dstSize) {
return false; // too big to allocate, abort
}
uint8_t* dp = SkMask::AllocImage(dstSize);
dst->fImage = dp;
int dstHeight = dst->fBounds.height();
int dstWidth = dst->fBounds.width();
uint8_t *outptr = dp;
SkAutoTMalloc<uint8_t> horizontalScanline(dstWidth);
SkAutoTMalloc<uint8_t> verticalScanline(dstHeight);
ComputeBlurredScanline(horizontalScanline, profile, dstWidth, sigma);
ComputeBlurredScanline(verticalScanline, profile, dstHeight, sigma);
for (int y = 0 ; y < dstHeight ; ++y) {
for (int x = 0 ; x < dstWidth ; x++) {
unsigned int maskval = SkMulDiv255Round(horizontalScanline[x], verticalScanline[y]);
*(outptr++) = maskval;
}
}
if (style == kInner_SkBlurStyle) {
// now we allocate the "real" dst, mirror the size of src
size_t srcSize = (size_t)(src.width() * src.height());
if (0 == srcSize) {
return false; // too big to allocate, abort
}
dst->fImage = SkMask::AllocImage(srcSize);
for (int y = 0 ; y < sh ; y++) {
uint8_t *blur_scanline = dp + (y+pad)*dstWidth + pad;
uint8_t *inner_scanline = dst->fImage + y*sw;
memcpy(inner_scanline, blur_scanline, sw);
}
SkMask::FreeImage(dp);
dst->fBounds.set(SkScalarRoundToInt(src.fLeft),
SkScalarRoundToInt(src.fTop),
SkScalarRoundToInt(src.fRight),
SkScalarRoundToInt(src.fBottom)); // restore trimmed bounds
dst->fRowBytes = sw;
} else if (style == kOuter_SkBlurStyle) {
for (int y = pad ; y < dstHeight-pad ; y++) {
uint8_t *dst_scanline = dp + y*dstWidth + pad;
memset(dst_scanline, 0, sw);
}
} else if (style == kSolid_SkBlurStyle) {
for (int y = pad ; y < dstHeight-pad ; y++) {
uint8_t *dst_scanline = dp + y*dstWidth + pad;
memset(dst_scanline, 0xff, sw);
}
}
// normal and solid styles are the same for analytic rect blurs, so don't
// need to handle solid specially.
return true;
}
bool SkBlurMask::BlurRRect(SkScalar sigma, SkMask *dst,
const SkRRect &src, SkBlurStyle style,
SkIPoint *margin, SkMask::CreateMode createMode) {
// Temporary for now -- always fail, should cause caller to fall back
// to old path. Plumbing just to land API and parallelize effort.
return false;
}
// The "simple" blur is a direct implementation of separable convolution with a discrete
// gaussian kernel. It's "ground truth" in a sense; too slow to be used, but very
// useful for correctness comparisons.
bool SkBlurMask::BlurGroundTruth(SkScalar sigma, SkMask* dst, const SkMask& src,
SkBlurStyle style, SkIPoint* margin) {
if (src.fFormat != SkMask::kA8_Format) {
return false;
}
float variance = sigma * sigma;
int windowSize = SkScalarCeilToInt(sigma*6);
// round window size up to nearest odd number
windowSize |= 1;
SkAutoTMalloc<float> gaussWindow(windowSize);
int halfWindow = windowSize >> 1;
gaussWindow[halfWindow] = 1;
float windowSum = 1;
for (int x = 1 ; x <= halfWindow ; ++x) {
float gaussian = expf(-x*x / (2*variance));
gaussWindow[halfWindow + x] = gaussWindow[halfWindow-x] = gaussian;
windowSum += 2*gaussian;
}
// leave the filter un-normalized for now; we will divide by the normalization
// sum later;
int pad = halfWindow;
if (margin) {
margin->set( pad, pad );
}
dst->fBounds = src.fBounds;
dst->fBounds.outset(pad, pad);
dst->fRowBytes = dst->fBounds.width();
dst->fFormat = SkMask::kA8_Format;
dst->fImage = nullptr;
if (src.fImage) {
size_t dstSize = dst->computeImageSize();
if (0 == dstSize) {
return false; // too big to allocate, abort
}
int srcWidth = src.fBounds.width();
int srcHeight = src.fBounds.height();
int dstWidth = dst->fBounds.width();
const uint8_t* srcPixels = src.fImage;
uint8_t* dstPixels = SkMask::AllocImage(dstSize);
SkAutoTCallVProc<uint8_t, SkMask_FreeImage> autoCall(dstPixels);
// do the actual blur. First, make a padded copy of the source.
// use double pad so we never have to check if we're outside anything
int padWidth = srcWidth + 4*pad;
int padHeight = srcHeight;
int padSize = padWidth * padHeight;
SkAutoTMalloc<uint8_t> padPixels(padSize);
memset(padPixels, 0, padSize);
for (int y = 0 ; y < srcHeight; ++y) {
uint8_t* padptr = padPixels + y * padWidth + 2*pad;
const uint8_t* srcptr = srcPixels + y * srcWidth;
memcpy(padptr, srcptr, srcWidth);
}
// blur in X, transposing the result into a temporary floating point buffer.
// also double-pad the intermediate result so that the second blur doesn't
// have to do extra conditionals.
int tmpWidth = padHeight + 4*pad;
int tmpHeight = padWidth - 2*pad;
int tmpSize = tmpWidth * tmpHeight;
SkAutoTMalloc<float> tmpImage(tmpSize);
memset(tmpImage, 0, tmpSize*sizeof(tmpImage[0]));
for (int y = 0 ; y < padHeight ; ++y) {
uint8_t *srcScanline = padPixels + y*padWidth;
for (int x = pad ; x < padWidth - pad ; ++x) {
float *outPixel = tmpImage + (x-pad)*tmpWidth + y + 2*pad; // transposed output
uint8_t *windowCenter = srcScanline + x;
for (int i = -pad ; i <= pad ; ++i) {
*outPixel += gaussWindow[pad+i]*windowCenter[i];
}
*outPixel /= windowSum;
}
}
// blur in Y; now filling in the actual desired destination. We have to do
// the transpose again; these transposes guarantee that we read memory in
// linear order.
for (int y = 0 ; y < tmpHeight ; ++y) {
float *srcScanline = tmpImage + y*tmpWidth;
for (int x = pad ; x < tmpWidth - pad ; ++x) {
float *windowCenter = srcScanline + x;
float finalValue = 0;
for (int i = -pad ; i <= pad ; ++i) {
finalValue += gaussWindow[pad+i]*windowCenter[i];
}
finalValue /= windowSum;
uint8_t *outPixel = dstPixels + (x-pad)*dstWidth + y; // transposed output
int integerPixel = int(finalValue + 0.5f);
*outPixel = SkClampMax( SkClampPos(integerPixel), 255 );
}
}
dst->fImage = dstPixels;
// if need be, alloc the "real" dst (same size as src) and copy/merge
// the blur into it (applying the src)
if (style == kInner_SkBlurStyle) {
// now we allocate the "real" dst, mirror the size of src
size_t srcSize = src.computeImageSize();
if (0 == srcSize) {
return false; // too big to allocate, abort
}
dst->fImage = SkMask::AllocImage(srcSize);
merge_src_with_blur(dst->fImage, src.fRowBytes,
srcPixels, src.fRowBytes,
dstPixels + pad*dst->fRowBytes + pad,
dst->fRowBytes, srcWidth, srcHeight);
SkMask::FreeImage(dstPixels);
} else if (style != kNormal_SkBlurStyle) {
clamp_with_orig(dstPixels + pad*dst->fRowBytes + pad,
dst->fRowBytes, srcPixels, src.fRowBytes, srcWidth, srcHeight, style);
}
(void)autoCall.release();
}
if (style == kInner_SkBlurStyle) {
dst->fBounds = src.fBounds; // restore trimmed bounds
dst->fRowBytes = src.fRowBytes;
}
return true;
}