OpenGL ES2.0贴图

1、定义传入着色器的顶点数据及索引

//传入结构体
typedef struct {
    float Position[3]; 
    float TexCoord[2];
} Vertex;
//顶点数据 
const Vertex Vertices[] = {
    {{1, -1, 0}, {1, 1}},
    {{1, 1, 0},{1, 0}},
    {{-1, 1, 0}, {0, 0}},
    {{-1, -1, 0},{0, 1}},
}; 
//顶点索引
const GLubyte Indices[] = { 
    0, 1, 2,
    2, 3, 0
};

2、生成图片纹理并获得其索引 方法

+ (GLuint)setupTexture:(UIImage *)pImage {
 
    CGImageRef spriteImage = pImage.CGImage;
    if (!spriteImage) {
        NSLog(@"Failed to load image ");
        exit(1);
    }
     
    size_t width = CGImageGetWidth(spriteImage);
    size_t height = CGImageGetHeight(spriteImage); 
    
    
    GLubyte * spriteData = (GLubyte *) calloc(width*height*4, sizeof(GLubyte));
    
    CGContextRef spriteContext = CGBitmapContextCreate(spriteData, width, height, 8, width*4,
                                                       CGImageGetColorSpace(spriteImage), kCGImageAlphaPremultipliedLast);
    
 
    CGContextDrawImage(spriteContext, CGRectMake(0, 0, width, height), spriteImage);
    
    CGContextRelease(spriteContext);
    
  
    GLuint texName;
    //生成纹理数
    glGenTextures(1, &texName);
    glBindTexture(GL_TEXTURE_2D, texName);
    
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    //生成图片纹理
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, spriteData);
    
    free(spriteData);        
    return texName;    
}

3、获取传入GLSL的槽位

 //获得图片纹理索引
 _imageTexture = [OpenGLHelper setupTexture:pImage];
//获得在GLSL中纹理的索引
   _texCoordSlot = glGetAttribLocation(_programHandle, "TexCoordIn");
    glEnableVertexAttribArray(_texCoordSlot);
    _textureUniform = glGetUniformLocation(_programHandle, "Texture");
//获得GLSL中顶点的索引
   _positionSlot = glGetAttribLocation(_programHandle, "vPosition");

4、在render(渲染)方法中加入

     //传入顶点着色器的数据
    glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE,
                          sizeof(Vertex), 0); 
    glVertexAttribPointer(_texCoordSlot, 2, GL_FLOAT, GL_FALSE,
                          sizeof(Vertex), (GLvoid*) (sizeof(float) * 3
                                                     ));
        
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, _imageTexture);
    glUniform1i(_textureUniform, 0);
   
    // 设置边缘截取模式  防止图片读取有问题
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    
    glDrawElements(GL_TRIANGLES, sizeof(Indices)/sizeof(Indices[0]),
                   GL_UNSIGNED_BYTE, 0);