Bug 1659015 - P1. Add YUV identity support (rgb) to WR. r=gw

Differential Revision: https://phabricator.services.mozilla.com/D87167

gfx/webrender_bindings/WebRenderTypes.h

@@ -780,6 +780,8 @@ static inline wr::WrYuvColorSpace ToWrYuvColorSpace(
       return wr::WrYuvColorSpace::Rec709;
     case gfx::YUVColorSpace::BT2020:
       return wr::WrYuvColorSpace::Rec2020;
+    case gfx::YUVColorSpace::Identity:
+      return wr::WrYuvColorSpace::Identity;
     default:
       MOZ_ASSERT_UNREACHABLE("Tried to convert invalid YUVColorSpace.");
   }

gfx/wr/webrender/res/brush_yuv_image.glsl

@@ -27,6 +27,7 @@ flat varying vec4 vUvBounds_V;
 
 flat varying float vCoefficient;
 flat varying mat3 vYuvColorMatrix;
+flat varying vec3 vYuvOffsetVector;
 flat varying int vFormat;
 
 #ifdef WR_VERTEX_SHADER
@@ -60,6 +61,7 @@ void yuv_brush_vs(
     vCoefficient = prim.coefficient;
 
     vYuvColorMatrix = get_yuv_color_matrix(prim.color_space);
+    vYuvOffsetVector = get_yuv_offset_vector(prim.color_space);
     vFormat = prim.yuv_format;
 
 #ifdef WR_FEATURE_ALPHA_PASS
@@ -94,6 +96,7 @@ Fragment yuv_brush_fs() {
     vec4 color = sample_yuv(
         vFormat,
         vYuvColorMatrix,
+        vYuvOffsetVector,
         vCoefficient,
         vYuvLayers,
         vUv_Y,

gfx/wr/webrender/res/composite.glsl

@@ -8,6 +8,7 @@
 
 #ifdef WR_FEATURE_YUV
 flat varying mat3 vYuvColorMatrix;
+flat varying vec3 vYuvOffsetVector;
 flat varying float vYuvCoefficient;
 flat varying int vYuvFormat;
 flat varying vec3 vYuvLayers;
@@ -59,6 +60,7 @@ void main(void) {
     float yuv_coefficient = aParams.w;
 
     vYuvColorMatrix = get_yuv_color_matrix(yuv_color_space);
+    vYuvOffsetVector = get_yuv_offset_vector(yuv_color_space);
     vYuvCoefficient = yuv_coefficient;
     vYuvFormat = yuv_format;
 
@@ -120,6 +122,7 @@ void main(void) {
     vec4 color = sample_yuv(
         vYuvFormat,
         vYuvColorMatrix,
+        vYuvOffsetVector,
         vYuvCoefficient,
         vYuvLayers,
         vUV_y,

gfx/wr/webrender/res/yuv.glsl

@@ -19,6 +19,7 @@
 #define YUV_COLOR_SPACE_REC601      0
 #define YUV_COLOR_SPACE_REC709      1
 #define YUV_COLOR_SPACE_REC2020     2
+#define YUV_COLOR_SPACE_IDENTITY    3
 
 // The constants added to the Y, U and V components are applied in the fragment shader.
 
@@ -64,17 +65,36 @@ const mat3 YuvColorMatrixRec2020 = mat3(
     1.67867410714286 , -0.650424318505057,  0.0
 );
 
+// The matrix is stored in column-major.
+// Identity is stored as GBR
+const mat3 IdentityColorMatrix = mat3(
+    0.0              ,  1.0,                0.0,
+    0.0              ,  0.0,                1.0,
+    1.0              ,  0.0,                0.0
+);
+
 mat3 get_yuv_color_matrix(int color_space) {
     switch (color_space) {
         case YUV_COLOR_SPACE_REC601:
             return YuvColorMatrixRec601;
         case YUV_COLOR_SPACE_REC709:
             return YuvColorMatrixRec709;
+        case YUV_COLOR_SPACE_IDENTITY:
+            return IdentityColorMatrix;
         default:
             return YuvColorMatrixRec2020;
     }
 }
 
+vec3 get_yuv_offset_vector(int color_space) {
+    switch (color_space) {
+        case YUV_COLOR_SPACE_IDENTITY:
+            return vec3(0.0, 0.0, 0.0);
+        default:
+            return vec3(0.06275, 0.50196, 0.50196);
+    }
+}
+
 void write_uv_rect(
     vec2 uv0,
     vec2 uv1,
@@ -99,6 +119,7 @@ void write_uv_rect(
 vec4 sample_yuv(
     int format,
     mat3 yuv_color_matrix,
+    vec3 yuv_offset_vector,
     float coefficient,
     vec3 yuv_layers,
     vec2 in_uv_y,
@@ -148,7 +169,7 @@ vec4 sample_yuv(
     }
 
     // See the YuvColorMatrix definition for an explanation of where the constants come from.
-    vec3 rgb = yuv_color_matrix * (yuv_value * coefficient - vec3(0.06275, 0.50196, 0.50196));
+    vec3 rgb = yuv_color_matrix * (yuv_value * coefficient - yuv_offset_vector);
     vec4 color = vec4(rgb, 1.0);
 
     return color;

gfx/wr/webrender_api/src/display_item.rs

@@ -1293,6 +1293,7 @@ pub enum YuvColorSpace {
     Rec601 = 0,
     Rec709 = 1,
     Rec2020 = 2,
+    Identity = 3, // aka RGB as per ISO/IEC 23091-2:2019
 }
 
 #[repr(u8)]