Fix boot animation alpha multiplication computations

Previously, this was resulting in the output color roughtly as

  output_n = color_n * mask_n^2 * (mask_0 + mask_1 + mask_2 + mask_3)

where n is a color channel between 0 and 3.

This caused extra aliasing around edges, since the alpha fades too
quickly along an edge.

Bug: 239632466
Bug: 258246539
Test: verify pixel values for boot animation match mask on watch + phone
Test: modify uFade value, verify pixel colors match
Change-Id: I86742a181576e684aa698a190a8766f4223de799

1 files changed, 15 insertions, 15 deletions

diff --git a/cmds/bootanimation/BootAnimation.cpp b/cmds/bootanimation/BootAnimation.cpp
index 50c8e933d25f..3f6046f01f11 100644
--- a/cmds/bootanimation/BootAnimation.cpp
+++ b/cmds/bootanimation/BootAnimation.cpp
@@ -132,14 +132,14 @@ static const char IMAGE_FRAG_DYNAMIC_COLORING_SHADER_SOURCE[] = R"(
     uniform sampler2D uTexture;
     uniform float uFade;
     uniform float uColorProgress;
-    uniform vec4 uStartColor0;
-    uniform vec4 uStartColor1;
-    uniform vec4 uStartColor2;
-    uniform vec4 uStartColor3;
-    uniform vec4 uEndColor0;
-    uniform vec4 uEndColor1;
-    uniform vec4 uEndColor2;
-    uniform vec4 uEndColor3;
+    uniform vec3 uStartColor0;
+    uniform vec3 uStartColor1;
+    uniform vec3 uStartColor2;
+    uniform vec3 uStartColor3;
+    uniform vec3 uEndColor0;
+    uniform vec3 uEndColor1;
+    uniform vec3 uEndColor2;
+    uniform vec3 uEndColor3;
     varying highp vec2 vUv;
     void main() {
         vec4 mask = texture2D(uTexture, vUv);
@@ -152,12 +152,12 @@ static const char IMAGE_FRAG_DYNAMIC_COLORING_SHADER_SOURCE[] = R"(
             * step(cWhiteMaskThreshold, g)
             * step(cWhiteMaskThreshold, b)
             * step(cWhiteMaskThreshold, a);
-        vec4 color = r * mix(uStartColor0, uEndColor0, uColorProgress)
+        vec3 color = r * mix(uStartColor0, uEndColor0, uColorProgress)
                 + g * mix(uStartColor1, uEndColor1, uColorProgress)
                 + b * mix(uStartColor2, uEndColor2, uColorProgress)
                 + a * mix(uStartColor3, uEndColor3, uColorProgress);
-        color = mix(color, vec4(vec3((r + g + b + a) * 0.25), 1.0), useWhiteMask);
-        gl_FragColor = vec4(color.x, color.y, color.z, (1.0 - uFade)) * color.a;
+        color = mix(color, vec3((r + g + b + a) * 0.25), useWhiteMask);
+        gl_FragColor = vec4(color.x, color.y, color.z, (1.0 - uFade));
     })";
 static const char IMAGE_FRAG_SHADER_SOURCE[] = R"(
     precision mediump float;
@@ -1440,12 +1440,12 @@ void BootAnimation::initDynamicColors() {
     for (int i = 0; i < DYNAMIC_COLOR_COUNT; i++) {
         float *startColor = mAnimation->startColors[i];
         float *endColor = mAnimation->endColors[i];
-        glUniform4f(glGetUniformLocation(mImageShader,
+        glUniform3f(glGetUniformLocation(mImageShader,
             (U_START_COLOR_PREFIX + std::to_string(i)).c_str()),
-            startColor[0], startColor[1], startColor[2], 1 /* alpha */);
-        glUniform4f(glGetUniformLocation(mImageShader,
+            startColor[0], startColor[1], startColor[2]);
+        glUniform3f(glGetUniformLocation(mImageShader,
             (U_END_COLOR_PREFIX + std::to_string(i)).c_str()),
-            endColor[0], endColor[1], endColor[2], 1 /* alpha */);
+            endColor[0], endColor[1], endColor[2]);
     }
     mImageColorProgressLocation = glGetUniformLocation(mImageShader, U_COLOR_PROGRESS);
 }