add sRGB pixel formats to the HALs

Change-Id: I1d5f9dd14a6485dd3a29fb5960edfa79aa86da42

1 files changed, 28 insertions, 1 deletions

diff --git a/include/system/graphics.h b/include/system/graphics.h
index ed493f5..2ddcc08 100644
--- a/include/system/graphics.h
+++ b/include/system/graphics.h
@@ -42,6 +42,13 @@ extern "C" {
  */
 
 enum {
+    /*
+     * "linear" color pixel formats:
+     *
+     * The pixel formats below contain sRGB data but are otherwise treated
+     * as linear formats, i.e.: no special operation is performed when
+     * reading or writing into a buffer in one of these formats
+     */
     HAL_PIXEL_FORMAT_RGBA_8888          = 1,
     HAL_PIXEL_FORMAT_RGBX_8888          = 2,
     HAL_PIXEL_FORMAT_RGB_888            = 3,
@@ -50,7 +57,27 @@ enum {
     HAL_PIXEL_FORMAT_RGBA_5551          = 6,
     HAL_PIXEL_FORMAT_RGBA_4444          = 7,
 
-    /* 0x8 - 0xFF range unavailable */
+    /*
+     * sRGB color pixel formats:
+     *
+     * The red, green and blue components are stored in sRGB space, and converted
+     * to linear space when read, using the standard sRGB to linear equation:
+     *
+     * Clinear = Csrgb / 12.92                  for Csrgb <= 0.04045
+     *         = (Csrgb + 0.055 / 1.055)^2.4    for Csrgb >  0.04045
+     *
+     * When written the inverse transformation is performed:
+     *
+     * Csrgb = 12.92 * Clinear                  for Clinear <= 0.0031308
+     *       = 1.055 * Clinear^(1/2.4) - 0.055  for Clinear >  0.0031308
+     *
+     *
+     *  The alpha component, if present, is always stored in linear space and
+     *  is left unmodified when read or written.
+     *
+     */
+    HAL_PIXEL_FORMAT_sRGB_A_8888        = 0xC,
+    HAL_PIXEL_FORMAT_sRGB_888           = 0xD,
 
     /*
      * 0x100 - 0x1FF