emulate srgb format for generateMipmap

gpu/command_buffer/service/gles2_cmd_srgb_converter.cc

Index: gpu/command_buffer/service/gles2_cmd_srgb_converter.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_srgb_converter.cc b/gpu/command_buffer/service/gles2_cmd_srgb_converter.cc
index ffbaf3059e5384432e264139e5a5b321788246b6..53d68225e098bb33913766509c6fccacdcadcc60 100644
--- a/gpu/command_buffer/service/gles2_cmd_srgb_converter.cc
+++ b/gpu/command_buffer/service/gles2_cmd_srgb_converter.cc
@@ -322,5 +322,265 @@ void SRGBConverter::Blit(
   decoder->RestoreGlobalState();
 }
 
+void SRGBConverter::InitializeSRGBEncoder(const gles2::GLES2Decoder* decoder) {
+  if (srgb_encoder_initialized_) {
+    return;
+  }
+
+  GLuint srgb_encoder_program_ = 0;
+
+  std::array<GLuint, 1> srgb_encoder_textures_ = {{0}};
+  GLuint srgb_encoder_fbo_ = 0;
+  GLuint srgb_encoder_vao_ = 0;
+
+  srgb_encoder_program_ = glCreateProgram();
+
+  const char* vs_source =
+      "#version 150\n"
+      "out vec2 v_texcoord;\n"
+      "\n"
+      "void main()\n"
+      "{\n"
+      "    const vec2 quad_positions[6] = vec2[6]\n"
+      "    (\n"
+      "        vec2(0.0f, 0.0f),\n"
+      "        vec2(0.0f, 1.0f),\n"
+      "        vec2(1.0f, 0.0f),\n"
+      "\n"
+      "        vec2(0.0f, 1.0f),\n"
+      "        vec2(1.0f, 0.0f),\n"
+      "        vec2(1.0f, 1.0f)\n"
+      "    );\n"
+      "\n"
+      "    vec2 xy = vec2((quad_positions[gl_VertexID] * 2.0) - 1.0);\n"
+      "    gl_Position = vec4(xy, 0.0, 1.0);\n"
+      "    v_texcoord = quad_positions[gl_VertexID];\n"
+      "}\n";
+
+  // Compile the vertex shader
+  GLuint vs = glCreateShader(GL_VERTEX_SHADER);
+  CompileShader(vs, vs_source);
+  glAttachShader(srgb_encoder_program_, vs);
+  glDeleteShader(vs);
+
+  // Compile the fragment shader
+
+  // Sampling texels from a srgb texture to a linear image, it will convert
+  // the srgb color space to linear color space automatically as a part of
+  // filtering. See the section <sRGB Texture Color Conversion> in GLES and
+  // OpenGL spec. So in decoder, we don't need to decode again.
+  // However, sampling texels from a linear texture to a srgb image, it will
+  // not convert linear to srgb automatically. Shader should always operates
+  // in linear space. So in encoder, we need to encode explicitly in shader.
+   const char* fs_source =
+       "#version 150\n"
+       "uniform sampler2D u_source_texture;\n"
+       "in vec2 v_texcoord;\n"
+       "out vec4 output_color;\n"
+       "\n"
+       "float encode(float color)\n"
+       "{\n"
+       "    float encoded_color;\n"
+       "    if (color <= 0.0) {\n"
+       "        return 0.0;\n"
+       "    } else if (color < 0.0031308) {\n"
+       "        return color * 12.92;\n"
+       "    } else if (color < 1) {\n"
+       "        return pow(color, 0.41666) * 1.055 - 0.055;\n"
+       "    } else {\n"
+       "        return 1.0;\n"
+       "    }\n"
+       "}\n"
+       "\n"
+       "void main()\n"
+       "{\n"
+       "    vec4 c = texture(u_source_texture, v_texcoord);\n"
+       "    output_color = vec4(encode(c.r), encode(c.g), encode(c.b), c.a);\n"
+       "}\n";
+ /* const char* fs_source =
+      "#version 150\n"
+      "uniform sampler2D u_source_texture;\n"
+      "in vec2 v_texcoord;\n"
+      "out vec4 output_color;\n"
+      "\n"
+      "void main()\n"
+      "{\n"
+      "    vec4 c = texture(u_source_texture, v_texcoord);\n"
+      "    output_color = c;\n"
+      "}\n";*/
+
+  GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
+  CompileShader(fs, fs_source);
+  glAttachShader(srgb_encoder_program_, fs);
+  glDeleteShader(fs);
+
+  glLinkProgram(srgb_encoder_program_);
+#ifndef NDEBUG
+  GLint linked = 0;
+  glGetProgramiv(srgb_encoder_program_, GL_LINK_STATUS, &linked);
+  if (!linked) {
+    DLOG(ERROR) << "SRGB Encoder for BlitFramebuffer: program link failure.";
+  }
+#endif
+
+  GLuint texture_uniform =
+      glGetUniformLocation(srgb_encoder_program_, "u_source_texture");
+  glUseProgram(srgb_encoder_program_);
+  glUniform1i(texture_uniform, 0);
+
+  glGenTextures(srgb_encoder_textures_.size(), srgb_encoder_textures_.data());
+  glActiveTexture(GL_TEXTURE0);
+  for (auto srgb_encoder_texture : srgb_encoder_textures_) {
+    glBindTexture(GL_TEXTURE_2D, srgb_encoder_texture);
+
+    // Use linear, non-mipmapped sampling with the srgb encoder texture
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+  }
+
+  glGenFramebuffersEXT(1, &srgb_encoder_fbo_);
+  glGenVertexArraysOES(1, &srgb_encoder_vao_);
+
+  decoder->RestoreTextureUnitBindings(0);
+  decoder->RestoreActiveTexture();
+  decoder->RestoreProgramBindings();
+
+  srgb_encoder_initialized_ = true;
+}

[yunchao, 2016/09/19 15:25:48]

Please remove this function above, Yizhou.

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+
+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);
+
+  GLenum error = glCheckFramebufferStatusEXT(GL_READ_FRAMEBUFFER);
+  error = glGetError();

[yunchao, 2016/09/19 15:25:48]

please remove the debugging code.

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+
+  glBindTexture(GL_TEXTURE_2D, srgb_converter_textures_[0]);
+  glTexImage2D(GL_TEXTURE_2D, 0, internal_format, width, height, 0, GL_SRGB,
+               GL_UNSIGNED_BYTE, nullptr);

[yunchao, 2016/09/19 15:25:48]

This is not necessary, copyTexImage2D will allocate storage for texture.
BTW, the format is not correct, it should be GL_RGBA, instead of GL_SRGB. 

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+  glCopyTexImage2D(GL_TEXTURE_2D, 0, internal_format, 0, 0, width, height, 0);
+  error = glGetError();
+  unsigned char bytes3[width * height * 4];
+  glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, bytes3);

[yunchao, 2016/09/19 15:25:48]

please remove debug code

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+
+  // 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);
+
+  error = glCheckFramebufferStatusEXT(GL_DRAW_FRAMEBUFFER);
+  error = glGetError();
+  unsigned char bytes2[width * height * 4];
+  glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, bytes2);

[yunchao, 2016/09/19 15:25:47]

remove debug code

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+ 
+  // bind texture with srgb format and render with srgb_decoder_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);
+  glEnable(GL_BLEND);

[yunchao, 2016/09/19 15:25:48]

glDisable blend

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+  glDisable(GL_DITHER);
+
+  glBindVertexArrayOES(srgb_converter_vao_);
+  glActiveTexture(GL_TEXTURE0);
+  glBindTexture(GL_TEXTURE_2D, srgb_converter_textures_[0]);
+
+  error = glGetError();

[yunchao, 2016/09/19 15:25:48]

remove debug code

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+
+  glDrawArrays(GL_TRIANGLES, 0, 6);
+
+  error = glGetError();
+  unsigned char bytes1[width * height * 4];
+  glBindFramebufferEXT(GL_READ_FRAMEBUFFER, srgb_decoder_fbo_);
+  glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, bytes1);

[yunchao, 2016/09/19 15:25:47]

remove debug code

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+
+  // 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);
+
+  error = glGetError();

[yunchao, 2016/09/19 15:25:47]

remove debug code

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+
+  // bind tex with rgba format and render with srgb_encoder_program_
+
+  glClearColor(0, 0, 0, 255);

[yunchao, 2016/09/19 15:25:47]

It is not necessary to set clear color.

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+  glBindTexture(GL_TEXTURE_2D, tex->service_id());
+  glBindFramebufferEXT(GL_FRAMEBUFFER, srgb_encoder_fbo_);
+
+  //InitializeSRGBEncoder(decoder);
+  //glUseProgram(srgb_encoder_program_);
+
+  /*glDeleteProgram(srgb_converter_program_);
+  srgb_converter_program_ = 0;
+  srgb_converter_initialized_ = false; 
+  InitializeSRGBConverterProgram();
+  */

[yunchao, 2016/09/19 15:25:47]

remove debug code.

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+  glUseProgram(srgb_converter_program_);
+ 
+  glBindVertexArrayOES(srgb_converter_vao_);

[yunchao, 2016/09/19 15:25:48]

These two lines are not necessary, you have called them already. 

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+
+  for (GLint level = base_level; level < mipmap_level; level++) {
+    glBindTexture(GL_TEXTURE_2D, tex->service_id());

[yunchao, 2016/09/19 15:25:47]

This is not necessary.

[yizhou.jiang, 2016/09/20 07:00:26]

Done.

+    glBindFramebufferEXT(GL_FRAMEBUFFER, srgb_encoder_fbo_);

[yunchao, 2016/09/19 15:25:48]

move this outside the for loop.

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+    glFramebufferTexture2DEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                              GL_TEXTURE_2D, tex->service_id(), level);
+
+    error = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER);
+    error = glGetError();
+    unsigned char bytes2[width * height * 4];
+    glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, bytes2);

[yunchao, 2016/09/19 15:25:48]

remove debug code.

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+
+    glActiveTexture(GL_TEXTURE0);

[yunchao, 2016/09/19 15:25:48]

This is not necessary.

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+    glBindTexture(GL_TEXTURE_2D, srgb_converter_textures_[1]);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, level);

[yunchao, 2016/09/19 15:25:48]

move these two lines outside the for loop.

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+    glViewport(0, 0, width, height);
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+
+    error = glGetError();
+    unsigned char bytes[width * height * 4];
+    glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, bytes);

[yunchao, 2016/09/19 15:25:48]

remove the debug code.

[yizhou.jiang, 2016/09/20 07:00:27]

Done.

+
+    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