CGImage 转 CVPixelBuffer

应用场景:把图像流放在OpenGL里渲染,需要进行一次转换

- (CVPixelBufferRef) pixelBufferFromCGImage: (CGImageRef) image
{
    CVPixelBufferRef pxbuffer = NULL;
    NSCParameterAssert(NULL != image);
    size_t originalWidth = CGImageGetWidth(image);
    size_t originalHeight = CGImageGetHeight(image);
    
    NSMutableData *imageData = [NSMutableData dataWithLength:originalWidth*originalHeight*4];
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef cgContext = CGBitmapContextCreate([imageData mutableBytes], originalWidth, originalHeight, 8, 4*originalWidth, colorSpace, kCGImageAlphaPremultipliedLast);
    CGColorSpaceRelease(colorSpace);
    CGContextDrawImage(cgContext, CGRectMake(0, 0, originalWidth, originalHeight), image);
    CGContextRelease(cgContext);
    CGImageRelease(image);
    unsigned char *pImageData = (unsigned char *)[imageData bytes];
    
    
    CFDictionaryRef empty;
    empty = CFDictionaryCreate(kCFAllocatorDefault, NULL, NULL,
                               0,
                               &kCFTypeDictionaryKeyCallBacks,
                               &kCFTypeDictionaryValueCallBacks);
    
    CFMutableDictionaryRef m_pPixelBufferAttribs = CFDictionaryCreateMutable(kCFAllocatorDefault,
                                                      3,
                                                      &kCFTypeDictionaryKeyCallBacks,
                                                      &kCFTypeDictionaryValueCallBacks);
    
    CFDictionarySetValue(m_pPixelBufferAttribs, kCVPixelBufferIOSurfacePropertiesKey, empty);
    CFDictionarySetValue(m_pPixelBufferAttribs, kCVPixelBufferOpenGLCompatibilityKey, empty);
    CFDictionarySetValue(m_pPixelBufferAttribs, kCVPixelBufferCGBitmapContextCompatibilityKey, empty);
    
    CVPixelBufferCreateWithBytes(kCFAllocatorDefault, originalWidth, originalHeight, kCVPixelFormatType_32BGRA, pImageData, originalWidth * 4, NULL, NULL, m_pPixelBufferAttribs, &pxbuffer);
    CFRelease(empty);
    CFRelease(m_pPixelBufferAttribs);
    
    
    return pxbuffer; 
}

注意colorspace 是否为RGB通道,如其他通道需替换相关参数:kCVPixelFormatType_32BGRA,CGColorSpaceCreateDeviceRGB