[OpenGL] use OpenGL shader to convert YUV to RGB-(GPU implementation is called directly, hardware-only, and high efficiency)

During this time, we have been engaged in video format conversion. Finally, we have successfully converted the YUV format of an image to the RGB format. The following is an introduction:

Because my project is in vs2008 and contains some related header files and libraries, I will only list some of the core code below, not all of the Code.

1. to download a file containing YUV data, you can also create one by yourself: YUV data file 2. Read the YUV data in the YUV data file. The key code is as follows: 2.1 read the file code.

unsigned char * readYUV(char *path){FILE *fp;unsigned char * buffer;long size = 1280 * 720 * 3 / 2;if((fp=fopen(path,"rb"))==NULL){   printf("cant open the file");   exit(0);}buffer = new unsigned char[size];memset(buffer,'\0',size);fread(buffer,size,1,fp);fclose(fp);return buffer;}

2.2 read data and create three textures for YUV data.

GLuint texYId;GLuint texUId;GLuint texVId;void loadYUV(){int width ;intheight ;width = 640;height = 480;unsigned char *buffer = NULL;buffer = readYUV("1.yuv");   glGenTextures ( 1, &texYId );   glBindTexture ( GL_TEXTURE_2D, texYId );   glTexImage2D ( GL_TEXTURE_2D, 0, GL_LUMINANCE, width, height, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, buffer );   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 );   glGenTextures ( 1, &texUId );   glBindTexture ( GL_TEXTURE_2D, texUId );   glTexImage2D ( GL_TEXTURE_2D, 0, GL_LUMINANCE, width / 2, height / 2, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, buffer + width * height);   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 );   glGenTextures ( 1, &texVId );   glBindTexture ( GL_TEXTURE_2D, texVId );   glTexImage2D ( GL_TEXTURE_2D, 0, GL_LUMINANCE, width / 2, height / 2, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, buffer + width * height * 5 / 4 );   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 );}

In the above Code, 1. YUV is the YUV data file. 3. Pass the texture to OpenGL shader for display.

3.1 vertex shader and fragment shader code

 GLbyte vShaderStr[] =        "attribute vec4 vPosition;    \n"  "attribute vec2 a_texCoord;\n"  "varying vec2 tc;\n"      "void main()                  \n"      "{                            \n"      "   gl_Position = vPosition;  \n"  "  tc = a_texCoord;\n"      "}                            \n";      GLbyte fShaderStr[] =        "precision mediump float;\n"  "uniform sampler2D tex_y;\n"  "uniform sampler2D tex_u;\n"  "uniform sampler2D tex_v;\n"  "varying vec2 tc;\n"      "void main()                                  \n"      "{                                            \n"  "  vec4 c = vec4((texture2D(tex_y, tc).r - 16./255.) * 1.164);\n"  "  vec4 U = vec4(texture2D(tex_u, tc).r - 128./255.);\n"  "  vec4 V = vec4(texture2D(tex_v, tc).r - 128./255.);\n"  "  c += V * vec4(1.596, -0.813, 0, 0);\n"  "  c += U * vec4(0, -0.392, 2.017, 0);\n"  "  c.a = 1.0;\n"  "  gl_FragColor = c;\n"      "}                                            \n";

The shader in the above part is obtained based on the YUV-to-RGB formula. That is to say, it is implemented in the shader. 4. The result is as follows: Note: The shader is in OpenGL ES format, which is slightly different from the shader in OpenGL format.

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