ios - 将 UIImage 数组导出到视频 - 蓝色结果

Question

我正在使用 AVAssetWriter 和 AVAssetWriterInputPixelBufferAdaptor 从 UIImage 数组制作视频。结果影片播放正常，但全都是蓝色调。我知道像素格式不正确，但还不足以解决问题。

AVAssetWriterInputPixelBufferAdaptor 代码:

NSDictionary *sourcePixelBufferAttributesDictionary = [NSDictionary dictionaryWithObjectsAndKeys:
                                                       [NSNumber numberWithInt:kCVPixelFormatType_32ARGB], kCVPixelBufferPixelFormatTypeKey, nil];

AVAssetWriterInputPixelBufferAdaptor *adaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput
                                                                                                                 sourcePixelBufferAttributes:sourcePixelBufferAttributesDictionary];

从CGImageRef生成CVPixelBufferRef

+ (CVPixelBufferRef)pixelBufferFromCGImage:(CGImageRef)image
{
    CGSize frameSize = CGSizeMake(CGImageGetWidth(image), CGImageGetHeight(image));
    NSDictionary *options = @{
                              (__bridge NSString *)kCVPixelBufferCGImageCompatibilityKey: @(NO),
                              (__bridge NSString *)kCVPixelBufferCGBitmapContextCompatibilityKey: @(NO)
                              };
    CVPixelBufferRef pixelBuffer;
    CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, frameSize.width,
                                          frameSize.height,  kCVPixelFormatType_32ARGB, (__bridge CFDictionaryRef) options,
                                          &pixelBuffer);
    if (status != kCVReturnSuccess) {
        return NULL;
    }

    CVPixelBufferLockBaseAddress(pixelBuffer, 0);
    void *data = CVPixelBufferGetBaseAddress(pixelBuffer);
    CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(data, frameSize.width, frameSize.height,
                                                 8, CVPixelBufferGetBytesPerRow(pixelBuffer), rgbColorSpace,
                                                 (CGBitmapInfo) kCGImageAlphaNoneSkipLast);
    CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image),
                                           CGImageGetHeight(image)), image);
    CGColorSpaceRelease(rgbColorSpace);
    CGContextRelease(context);
    CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);

    return pixelBuffer;
}

有什么建议吗？

Answer 1

调用 CGBitmapContextCreate 时，您应该传递 kCGImageAlphaNoneSkipFirst 而不是 kCGImageAlphaNoneSkipLast。

这是因为您的位图布局为 alpha 然后颜色，而不是颜色然后 alpha。

之所以会出现蓝色调，是因为您将 ARG 视为 RGB。 A (alpha) 为零，因此您的图像中没有红色。一般来说，从图像中去除所有红色会给您带来蓝绿色调。