color blindness enhancement

This is an attempt at improving the experience of
users with color vision impairement.

At this time this feature can only be enabled for
debugging:

  adb shell service call SurfaceFlinger 1014 i32 PARAM

  with PARAM:
   0 : disabled
   1 : protanomaly/protanopia simulation
   2 : deuteranomaly/deuteranopia simulation
   3 : tritanopia/tritanomaly simulation
  11, 12, 13: same as above w/ attempted correction/enhancement

The enhancement algorithm tries to spread the "error"
such that tones that would otherwise appear similar can be
distinguished.

Bug: 9465644

Change-Id: I860f7eed0cb81f54ef9cf24ad78155b6395ade48

2 files changed, 242 insertions, 0 deletions

diff --git a/services/surfaceflinger/Effects/Daltonizer.cpp b/services/surfaceflinger/Effects/Daltonizer.cpp
new file mode 100644
index 0000000..f384ba4
--- /dev/null
+++ b/services/surfaceflinger/Effects/Daltonizer.cpp
@@ -0,0 +1,183 @@
+/*
+ * 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 <ui/mat4.h>
+
+namespace android {
+
+Daltonizer::Daltonizer() :
+    mType(deuteranomaly), mMode(simulation), mDirty(true) {
+}
+
+Daltonizer::~Daltonizer() {
+}
+
+void Daltonizer::setType(Daltonizer::ColorBlindnessTypes type) {
+    if (type != mType) {
+        mDirty = true;
+        mType = type;
+    }
+}
+
+void Daltonizer::setMode(Daltonizer::Mode mode) {
+    if (mode != mMode) {
+        mDirty = true;
+        mMode = mode;
+    }
+}
+
+const mat4& Daltonizer::operator()() {
+    if (mDirty) {
+        mDirty = false;
+        update();
+    }
+    return mColorTransform;
+}
+
+void Daltonizer::update() {
+    // 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);
+
+    // control: simulation post-correction (used for debugging):
+    // set to identity or lms2lmsp, lms2lmsd, lms2lmst
+    mat4 control;
+    switch (mType) {
+        case protanopia:
+        case protanomaly:
+            simulation = lms2lmsp;
+            if (mMode == Daltonizer::correction)
+                correction = errp;
+            break;
+        case deuteranopia:
+        case deuteranomaly:
+            simulation = lms2lmsd;
+            if (mMode == Daltonizer::correction)
+                correction = errd;
+            break;
+        case tritanopia:
+        case tritanomaly:
+            simulation = lms2lmst;
+            if (mMode == Daltonizer::correction)
+                correction = errt;
+            break;
+    }
+
+    if (true) {
+        control = simulation;
+    }
+
+    mColorTransform = lms2rgb * control *
+            (simulation * rgb2lms + correction * (rgb2lms - simulation * rgb2lms));
+}
+
+} /* namespace android */
diff --git a/services/surfaceflinger/Effects/Daltonizer.h b/services/surfaceflinger/Effects/Daltonizer.h
new file mode 100644
index 0000000..e816437
--- /dev/null
+++ b/services/surfaceflinger/Effects/Daltonizer.h
@@ -0,0 +1,59 @@
+/*
+ * 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.
+ */
+
+#ifndef SF_EFFECTS_DALTONIZER_H_
+#define SF_EFFECTS_DALTONIZER_H_
+
+#include <ui/mat4.h>
+
+namespace android {
+
+class Daltonizer {
+public:
+    enum ColorBlindnessTypes {
+        protanopia,         // L (red) cone missing
+        deuteranopia,       // M (green) cone missing
+        tritanopia,         // S (blue) cone missing
+        protanomaly,        // L (red) cone deficient
+        deuteranomaly,      // M (green) cone deficient (most common)
+        tritanomaly         // S (blue) cone deficient
+    };
+
+    enum Mode {
+        simulation,
+        correction
+    };
+
+    Daltonizer();
+    ~Daltonizer();
+
+    void setType(ColorBlindnessTypes type);
+    void setMode(Mode mode);
+
+    // returns the color transform to apply in the shader
+    const mat4& operator()();
+
+private:
+    void update();
+
+    ColorBlindnessTypes mType;
+    Mode mMode;
+    bool mDirty;
+    mat4 mColorTransform;
+};
+
+} /* namespace android */
+#endif /* SF_EFFECTS_DALTONIZER_H_ */