1/*
2 * Copyright 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include "Daltonizer.h"
18#include <ui/mat4.h>
19
20namespace android {
21
22Daltonizer::Daltonizer() :
23    mType(deuteranomaly), mMode(simulation), mDirty(true) {
24}
25
26Daltonizer::~Daltonizer() {
27}
28
29void Daltonizer::setType(Daltonizer::ColorBlindnessTypes type) {
30    if (type != mType) {
31        mDirty = true;
32        mType = type;
33    }
34}
35
36void Daltonizer::setMode(Daltonizer::Mode mode) {
37    if (mode != mMode) {
38        mDirty = true;
39        mMode = mode;
40    }
41}
42
43const mat4& Daltonizer::operator()() {
44    if (mDirty) {
45        mDirty = false;
46        update();
47    }
48    return mColorTransform;
49}
50
51void Daltonizer::update() {
52    // converts a linear RGB color to the XYZ space
53    const mat4 rgb2xyz( 0.4124, 0.2126, 0.0193, 0,
54                        0.3576, 0.7152, 0.1192, 0,
55                        0.1805, 0.0722, 0.9505, 0,
56                        0     , 0     , 0     , 1);
57
58    // converts a XYZ color to the LMS space.
59    const mat4 xyz2lms( 0.7328,-0.7036, 0.0030, 0,
60                        0.4296, 1.6975, 0.0136, 0,
61                       -0.1624, 0.0061, 0.9834, 0,
62                        0     , 0     , 0     , 1);
63
64    // Direct conversion from linear RGB to LMS
65    const mat4 rgb2lms(xyz2lms*rgb2xyz);
66
67    // And back from LMS to linear RGB
68    const mat4 lms2rgb(inverse(rgb2lms));
69
70    // To simulate color blindness we need to "remove" the data lost by the absence of
71    // a cone. This cannot be done by just zeroing out the corresponding LMS component
72    // because it would create a color outside of the RGB gammut.
73    // Instead we project the color along the axis of the missing component onto a plane
74    // within the RGB gammut:
75    //  - since the projection happens along the axis of the missing component, a
76    //    color blind viewer perceives the projected color the same.
77    //  - We use the plane defined by 3 points in LMS space: black, white and
78    //    blue and red for protanopia/deuteranopia and tritanopia respectively.
79
80    // LMS space red
81    const vec3& lms_r(rgb2lms[0].rgb);
82    // LMS space blue
83    const vec3& lms_b(rgb2lms[2].rgb);
84    // LMS space white
85    const vec3 lms_w((rgb2lms * vec4(1)).rgb);
86
87    // To find the planes we solve the a*L + b*M + c*S = 0 equation for the LMS values
88    // of the three known points. This equation is trivially solved, and has for
89    // solution the following cross-products:
90    const vec3 p0 = cross(lms_w, lms_b);    // protanopia/deuteranopia
91    const vec3 p1 = cross(lms_w, lms_r);    // tritanopia
92
93    // The following 3 matrices perform the projection of a LMS color onto the given plane
94    // along the selected axis
95
96    // projection for protanopia (L = 0)
97    const mat4 lms2lmsp(  0.0000, 0.0000, 0.0000, 0,
98                    -p0.y / p0.x, 1.0000, 0.0000, 0,
99                    -p0.z / p0.x, 0.0000, 1.0000, 0,
100                          0     , 0     , 0     , 1);
101
102    // projection for deuteranopia (M = 0)
103    const mat4 lms2lmsd(  1.0000, -p0.x / p0.y, 0.0000, 0,
104                          0.0000,       0.0000, 0.0000, 0,
105                          0.0000, -p0.z / p0.y, 1.0000, 0,
106                          0     ,       0     , 0     , 1);
107
108    // projection for tritanopia (S = 0)
109    const mat4 lms2lmst(  1.0000, 0.0000, -p1.x / p1.z, 0,
110                          0.0000, 1.0000, -p1.y / p1.z, 0,
111                          0.0000, 0.0000,       0.0000, 0,
112                          0     ,       0     , 0     , 1);
113
114    // We will calculate the error between the color and the color viewed by
115    // a color blind user and "spread" this error onto the healthy cones.
116    // The matrices below perform this last step and have been chosen arbitrarily.
117
118    // The amount of correction can be adjusted here.
119
120    // error spread for protanopia
121    const mat4 errp(    1.0, 0.7, 0.7, 0,
122                        0.0, 1.0, 0.0, 0,
123                        0.0, 0.0, 1.0, 0,
124                          0,   0,   0, 1);
125
126    // error spread for deuteranopia
127    const mat4 errd(    1.0, 0.0, 0.0, 0,
128                        0.7, 1.0, 0.7, 0,
129                        0.0, 0.0, 1.0, 0,
130                          0,   0,   0, 1);
131
132    // error spread for tritanopia
133    const mat4 errt(    1.0, 0.0, 0.0, 0,
134                        0.0, 1.0, 0.0, 0,
135                        0.7, 0.7, 1.0, 0,
136                          0,   0,   0, 1);
137
138    const mat4 identity;
139
140    // And the magic happens here...
141    // We construct the matrix that will perform the whole correction.
142
143    // simulation: type of color blindness to simulate:
144    // set to either lms2lmsp, lms2lmsd, lms2lmst
145    mat4 simulation;
146
147    // correction: type of color blindness correction (should match the simulation above):
148    // set to identity, errp, errd, errt ([0] for simulation only)
149    mat4 correction(0);
150
151    switch (mType) {
152        case protanopia:
153        case protanomaly:
154            simulation = lms2lmsp;
155            if (mMode == Daltonizer::correction)
156                correction = errp;
157            break;
158        case deuteranopia:
159        case deuteranomaly:
160            simulation = lms2lmsd;
161            if (mMode == Daltonizer::correction)
162                correction = errd;
163            break;
164        case tritanopia:
165        case tritanomaly:
166            simulation = lms2lmst;
167            if (mMode == Daltonizer::correction)
168                correction = errt;
169            break;
170    }
171
172    mColorTransform = lms2rgb *
173        (simulation * rgb2lms + correction * (rgb2lms - simulation * rgb2lms));
174}
175
176} /* namespace android */
177