Tile Compression

gpu/command_buffer/common/gles2_cmd_utils.cc

Index: gpu/command_buffer/common/gles2_cmd_utils.cc
diff --git a/gpu/command_buffer/common/gles2_cmd_utils.cc b/gpu/command_buffer/common/gles2_cmd_utils.cc
index 0c2f493c6e63592321dd41f5167d6ca7834282f5..164981e75a4cbd4a9662fb103dcf6d438a3add01 100644
--- a/gpu/command_buffer/common/gles2_cmd_utils.cc
+++ b/gpu/command_buffer/common/gles2_cmd_utils.cc
@@ -468,6 +468,76 @@ bool GLES2Util::ComputeImageDataSizes(
   return true;
 }
 
+namespace {
+
+const int kS3TCBlockWidth = 4;
+const int kS3TCBlockHeight = 4;
+const int kS3TCDXT1BlockSize = 8;
+const int kS3TCDXT3AndDXT5BlockSize = 16;
+const int kETC1BlockWidth = 4;
+const int kETC1BlockHeight = 4;
+const int kETC1BlockSize = 8;
+
+bool IsValidDXTSize(GLint level, GLsizei size) {
+  return (size == 1) || (size == 2) || !(size % kS3TCBlockWidth);
+}
+
+}  // anonymous namespace.
+
+bool GLES2Util::ComputeCompressedImageSize(int width,
+                                           int height,
+                                           int format,
+                                           int* ret_size) {
+  switch (format) {
+    case GL_ATC_RGB_AMD:
+    case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
+    case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT: {
+      int num_blocks_across = (width + kS3TCBlockWidth - 1) / kS3TCBlockWidth;
+      int num_blocks_down = (height + kS3TCBlockHeight - 1) / kS3TCBlockHeight;
+      int num_blocks = num_blocks_across * num_blocks_down;
+      *ret_size = num_blocks * kS3TCDXT1BlockSize;
+      return true;
+    }
+    case GL_ATC_RGBA_INTERPOLATED_ALPHA_AMD:
+    case GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
+    case GL_COMPRESSED_RGBA_S3TC_DXT5_EXT: {
+      int num_blocks_across = (width + kS3TCBlockWidth - 1) / kS3TCBlockWidth;
+      int num_blocks_down = (height + kS3TCBlockHeight - 1) / kS3TCBlockHeight;
+      int num_blocks = num_blocks_across * num_blocks_down;
+      *ret_size = num_blocks * kS3TCDXT3AndDXT5BlockSize;
+      return true;
+    }
+    case GL_ETC1_RGB8_OES: {
+      int num_blocks_across = (width + kETC1BlockWidth - 1) / kETC1BlockWidth;
+      int num_blocks_down = (height + kETC1BlockHeight - 1) / kETC1BlockHeight;
+      int num_blocks = num_blocks_across * num_blocks_down;
+      *ret_size = num_blocks * kETC1BlockSize;
+      return true;
+    }
+  }
+
+  return false;
+}
+
+bool GLES2Util::IsValidCompressedImageSize(int level,
+                                           int width,
+                                           int height,
+                                           int format) {
+  switch (format) {
+    case GL_ATC_RGB_AMD:
+    case GL_ATC_RGBA_INTERPOLATED_ALPHA_AMD:
+    case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
+    case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
+    case GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
+    case GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
+      return IsValidDXTSize(level, width) && IsValidDXTSize(level, height);
+    case GL_ETC1_RGB8_OES:
+      return width > 0 && height > 0;
+    default:
+      return false;
+  }
+}
+
 size_t GLES2Util::RenderbufferBytesPerPixel(int format) {
   switch (format) {
     case GL_STENCIL_INDEX8: