openGL資料儲存為圖片

-(UIImage *)glToUIImageInRect:(CGRect)rect {
    
    NSInteger width = (NSInteger)rect.size.width;  // 960
    NSInteger height = (NSInteger)rect.size.height;  // 640
    NSInteger myDataLength = width * height * 4;
    
    // allocate array and read pixels into it.
    GLubyte *buffer = (GLubyte *) malloc(myDataLength);
    
    glReadPixels(rect.origin.x, rect.origin.y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
    
    GLubyte *buffer2 = (GLubyte *) malloc(myDataLength);
    for(int y = 0; y < height; y++)
    {
        for(int x = 0; x <width * 4; x++)
        {
//            buffer2[(height - 1 - y) * height * 4 + x] = buffer[y * 4 * height + x];
            buffer2[(height - 1 - y) * width * 4 + x] = buffer[y * 4 * width + x];
        }
    }
    
    CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer2, myDataLength, NULL);
    
    // prep the ingredients
    int bitsPerComponent = 8;
    int bitsPerPixel = 32;
//    int bytesPerRow = 4 * height;
    int bytesPerRow = 4 * width;
    CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
    CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
    CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
    
    // make the cgimage
    CGImageRef imageRef = CGImageCreate(width, height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
    
    // then make the uiimage from that
    UIImage *retImg = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    CGColorSpaceRelease(colorSpaceRef);
    CGDataProviderRelease(provider);
    
    return retImg;
}