emulate srgb format for generateMipmap

gpu/command_buffer/service/gles2_cmd_srgb_converter.cc

 // Copyright (c) 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "gpu/command_buffer/service/gles2_cmd_srgb_converter.h"
 
 #include "gpu/command_buffer/service/texture_manager.h"
 #include "ui/gl/gl_version_info.h"
 
 namespace {
@@ skipping 304 matching lines @@
   // Restore state
   decoder->RestoreAllAttributes();
   decoder->RestoreTextureUnitBindings(0);
   decoder->RestoreActiveTexture();
   decoder->RestoreProgramBindings();
   decoder->RestoreBufferBindings();
   decoder->RestoreFramebufferBindings();
   decoder->RestoreGlobalState();
 }
 
+void SRGBConverter::SRGBGenerateMipmap(const gles2::GLES2Decoder* decoder,
+                                       Texture* tex,
+                                       GLenum target) {
+  DCHECK(srgb_converter_initialized_);
+
+  GLsizei width;
+  GLsizei height;
+  GLsizei depth;
+  GLenum type = 0;
+  GLenum internal_format = 0;
+  GLsizei base_level = tex->base_level();
+  tex->GetLevelSize(target, base_level, &width, &height, &depth);
+  tex->GetLevelType(target, 0, &type, &internal_format);
+  const GLint mipmap_level =
+      TextureManager::ComputeMipMapCount(target, width, height, depth);
+
+  // copy tex to srgb_decoder_textures_[0] with srgb format
+  glBindTexture(target, tex->service_id());
+  glBindFramebufferEXT(GL_READ_FRAMEBUFFER, srgb_decoder_fbo_);
+  glFramebufferTexture2DEXT(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                            GL_TEXTURE_2D, tex->service_id(), 0);
+
+  glBindTexture(GL_TEXTURE_2D, srgb_converter_textures_[0]);
+  glTexImage2D(GL_TEXTURE_2D, 0, internal_format, width, height, 0, GL_SRGB,
+               GL_UNSIGNED_BYTE, nullptr);
+  glCopyTexImage2D(GL_TEXTURE_2D, 0, internal_format, 0, 0, width, height, 0);
+
+  // bind srgb_decoder_textures_[1] to draw framebuffer
+  glBindTexture(GL_TEXTURE_2D, srgb_converter_textures_[1]);
+  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA,
+               GL_UNSIGNED_BYTE, nullptr);
+  glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER, srgb_decoder_fbo_);
+  glFramebufferTexture2DEXT(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                            GL_TEXTURE_2D, srgb_converter_textures_[1], 0);
+
+  // bind texture with srgb format and render with srgb_converter_program_
+  glUseProgram(srgb_converter_program_);
+  glViewport(0, 0, width, height);
+  glDisable(GL_SCISSOR_TEST);
+  glDisable(GL_DEPTH_TEST);
+  glDisable(GL_STENCIL_TEST);
+  glDisable(GL_CULL_FACE);
+  glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
+  glDepthMask(GL_FALSE);
+  glDisable(GL_BLEND);
+  glDisable(GL_DITHER);
+
+  glBindVertexArrayOES(srgb_converter_vao_);
+  glActiveTexture(GL_TEXTURE0);
+  glBindTexture(GL_TEXTURE_2D, srgb_converter_textures_[0]);
+  glDrawArrays(GL_TRIANGLES, 0, 6);
+
+  // generateMipmap for tex and srgb_decoder_textures_[1]
+  glBindTexture(GL_TEXTURE_2D, tex->service_id());
+  glGenerateMipmapEXT(GL_TEXTURE_2D);
+  glBindTexture(GL_TEXTURE_2D, srgb_converter_textures_[1]);
+  glGenerateMipmapEXT(GL_TEXTURE_2D);
+
+  // bind tex with rgba format and render with srgb_converter_program_
+  glUseProgram(srgb_converter_program_);
+  glBindVertexArrayOES(srgb_converter_vao_);
+
+  for (GLint level = base_level; level < mipmap_level; level++) {
+    glBindTexture(GL_TEXTURE_2D, tex->service_id());
+    glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER, srgb_encoder_fbo_);
+    glFramebufferTexture2DEXT(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                              GL_TEXTURE_2D, tex->service_id(), level);
+
+    glActiveTexture(GL_TEXTURE0);
+    glBindTexture(GL_TEXTURE_2D, srgb_converter_textures_[1]);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, level);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
+                    GL_NEAREST_MIPMAP_NEAREST);
+
+    glViewport(0, 0, width, height);
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+    width /= 2;
+    height /= 2;
+  }
+
+  // Restore state
+  decoder->RestoreAllAttributes();
+  decoder->RestoreTextureUnitBindings(0);
+  decoder->RestoreActiveTexture();
+  decoder->RestoreProgramBindings();
+  decoder->RestoreBufferBindings();
+  decoder->RestoreFramebufferBindings();
+  decoder->RestoreGlobalState();
+}
+
 }  // namespace gles2.
 }  // namespace gpu