/*
* Copyright 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "Daltonizer.h"
#include <math/mat4.h>
namespace android {
void Daltonizer::setType(ColorBlindnessType type) {
if (type != mType) {
mDirty = true;
mType = type;
}
}
void Daltonizer::setMode(ColorBlindnessMode mode) {
if (mode != mMode) {
mDirty = true;
mMode = mode;
}
}
const mat4& Daltonizer::operator()() {
if (mDirty) {
mDirty = false;
update();
}
return mColorTransform;
}
void Daltonizer::update() {
if (mType == ColorBlindnessType::None) {
mColorTransform = mat4();
return;
}
// converts a linear RGB color to the XYZ space
const mat4 rgb2xyz( 0.4124, 0.2126, 0.0193, 0,
0.3576, 0.7152, 0.1192, 0,
0.1805, 0.0722, 0.9505, 0,
0 , 0 , 0 , 1);
// converts a XYZ color to the LMS space.
const mat4 xyz2lms( 0.7328,-0.7036, 0.0030, 0,
0.4296, 1.6975, 0.0136, 0,
-0.1624, 0.0061, 0.9834, 0,
0 , 0 , 0 , 1);
// Direct conversion from linear RGB to LMS
const mat4 rgb2lms(xyz2lms*rgb2xyz);
// And back from LMS to linear RGB
const mat4 lms2rgb(inverse(rgb2lms));
// To simulate color blindness we need to "remove" the data lost by the absence of
// a cone. This cannot be done by just zeroing out the corresponding LMS component
// because it would create a color outside of the RGB gammut.
// Instead we project the color along the axis of the missing component onto a plane
// within the RGB gammut:
// - since the projection happens along the axis of the missing component, a
// color blind viewer perceives the projected color the same.
// - We use the plane defined by 3 points in LMS space: black, white and
// blue and red for protanopia/deuteranopia and tritanopia respectively.
// LMS space red
const vec3& lms_r(rgb2lms[0].rgb);
// LMS space blue
const vec3& lms_b(rgb2lms[2].rgb);
// LMS space white
const vec3 lms_w((rgb2lms * vec4(1)).rgb);
// To find the planes we solve the a*L + b*M + c*S = 0 equation for the LMS values
// of the three known points. This equation is trivially solved, and has for
// solution the following cross-products:
const vec3 p0 = cross(lms_w, lms_b); // protanopia/deuteranopia
const vec3 p1 = cross(lms_w, lms_r); // tritanopia
// The following 3 matrices perform the projection of a LMS color onto the given plane
// along the selected axis
// projection for protanopia (L = 0)
const mat4 lms2lmsp( 0.0000, 0.0000, 0.0000, 0,
-p0.y / p0.x, 1.0000, 0.0000, 0,
-p0.z / p0.x, 0.0000, 1.0000, 0,
0 , 0 , 0 , 1);
// projection for deuteranopia (M = 0)
const mat4 lms2lmsd( 1.0000, -p0.x / p0.y, 0.0000, 0,
0.0000, 0.0000, 0.0000, 0,
0.0000, -p0.z / p0.y, 1.0000, 0,
0 , 0 , 0 , 1);
// projection for tritanopia (S = 0)
const mat4 lms2lmst( 1.0000, 0.0000, -p1.x / p1.z, 0,
0.0000, 1.0000, -p1.y / p1.z, 0,
0.0000, 0.0000, 0.0000, 0,
0 , 0 , 0 , 1);
// We will calculate the error between the color and the color viewed by
// a color blind user and "spread" this error onto the healthy cones.
// The matrices below perform this last step and have been chosen arbitrarily.
// The amount of correction can be adjusted here.
// error spread for protanopia
const mat4 errp( 1.0, 0.7, 0.7, 0,
0.0, 1.0, 0.0, 0,
0.0, 0.0, 1.0, 0,
0, 0, 0, 1);
// error spread for deuteranopia
const mat4 errd( 1.0, 0.0, 0.0, 0,
0.7, 1.0, 0.7, 0,
0.0, 0.0, 1.0, 0,
0, 0, 0, 1);
// error spread for tritanopia
const mat4 errt( 1.0, 0.0, 0.0, 0,
0.0, 1.0, 0.0, 0,
0.7, 0.7, 1.0, 0,
0, 0, 0, 1);
const mat4 identity;
// And the magic happens here...
// We construct the matrix that will perform the whole correction.
// simulation: type of color blindness to simulate:
// set to either lms2lmsp, lms2lmsd, lms2lmst
mat4 simulation;
// correction: type of color blindness correction (should match the simulation above):
// set to identity, errp, errd, errt ([0] for simulation only)
mat4 correction(0);
switch (mType) {
case ColorBlindnessType::Protanomaly:
simulation = lms2lmsp;
if (mMode == ColorBlindnessMode::Correction)
correction = errp;
break;
case ColorBlindnessType::Deuteranomaly:
simulation = lms2lmsd;
if (mMode == ColorBlindnessMode::Correction)
correction = errd;
break;
case ColorBlindnessType::Tritanomaly:
simulation = lms2lmst;
if (mMode == ColorBlindnessMode::Correction)
correction = errt;
break;
case ColorBlindnessType::None:
// We already caught this at the beginning of the method, but the
// compiler doesn't know that
break;
}
mColorTransform = lms2rgb *
(simulation * rgb2lms + correction * (rgb2lms - simulation * rgb2lms));
}
} /* namespace android */