OpenGL ES转换YUV数据到RGB格式

在OpenGL ES中将YUV数据转换为RGB格式需要进行以下步骤：

1. 创建一个纹理对象，用于存储转换后的RGB数据。
2. 将YUV数据绑定到一个纹理单元上。
3. 创建一个着色器程序，用于将YUV数据转换为RGB格式。
4. 将纹理对象绑定到FBO（Frame Buffer Object），并将着色器程序与FBO绑定。
5. 渲染FBO以将YUV数据转换为RGB格式。

下面是一个简单的代码示例：

1. 创建纹理对象

GLuint textureID;
glGenTextures(1, &textureID);
glBindTexture(GL_TEXTURE_2D, textureID);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
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);

2. 绑定YUV数据到纹理单元

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, textureID);
glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, width, height, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, yData);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, textureID);
glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE_ALPHA, width / 2, height / 2, 0, GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, uvData);

3. 创建着色器程序

const char* vertexShader =
    "attribute vec4 position;\n"
    "attribute vec2 texCoord;\n"
    "varying vec2 v_texCoord;\n"
    "void main()\n"
    "{\n"
    "    gl_Position = position;\n"
    "    v_texCoord = texCoord;\n"
    "}\n";

const char* fragmentShader =
    "precision highp float;\n"
    "varying vec2 v_texCoord;\n"
    "uniform sampler2D yTexture;\n"
    "uniform sampler2D uvTexture;\n"
    "void main()\n"
    "{\n"
    "    float y = texture2D(yTexture, v_texCoord).r;\n"
    "    float u = texture2D(uvTexture, v_texCoord).r - 0.5;\n"
    "    float v = texture2D(uvTexture, v_texCoord).a - 0.5;\n"
    "    float r = y + 1.13983 * v;\n"
    "    float g = y - 0.39465 * u - 0.58060 * v;\n"
    "    float b = y + 2.03211 * u;\n"
    "    gl_FragColor = vec4(r, g, b, 1.0);\n"
    "}\n";

GLuint programID = glCreateProgram();
GLuint vertexShaderID = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShaderID, 1, &vertexShader, NULL);
glCompileShader(vertexShaderID);
glAttachShader(programID, vertexShaderID);
GLuint fragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShaderID, 1, &fragmentShader, NULL);
glCompileShader(fragmentShaderID);
glAttachShader(programID, fragmentShaderID);
glLinkProgram(programID);
glUseProgram(programID);

4. 绑定纹理对象到FBO，并将着色器程序与FBO绑定

GLuint fboID;
glGenFramebuffers(1, &fboID);
glBindFramebuffer(GL_FRAMEBUFFER, fboID);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textureID, 0);
glViewport(0, 0, width, height);
glUseProgram(programID);
glUniform1i(glGetUniformLocation(programID, "yTexture"), 0);
glUniform1i(glGetUniformLocation(programID, "uvTexture"), 1);

5. 渲染FBO

GLfloat vertices[] = {
    -1.0f,  1.0f, 0.0f, 1.0f,
    -1.0f, -1.0f, 0.0f, 0.0f,
     1.0f,  1.0f, 1.0f, 1.0f,
     1.0f, -1.0f, 1.0f, 0.0f
};
GLubyte indices[] = {0, 1, 2, 3};
glVertexAttribPointer(glGetAttribLocation(programID, "position"), 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), vertices);
glVertexAttribPointer(glGetAttribLocation(programID, "texCoord"), 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), vertices + 2);
glEnableVertexAttribArray(glGetAttribLocation(programID, "position"));
glEnableVertexAttribArray(glGetAttribLocation(programID, "texCoord"));
glDrawElements(GL_TRIANGLE_STRIP, 4, GL_UNSIGNED_BYTE, indices);
glDisableVertexAttribArray(glGetAttribLocation(programID, "position"));
glDisableVertexAttribArray(glGetAttribLocation(programID, "texCoord"));