4

I want to write all frames to disk using QTKit.framework for camera input. But all the images I get are half transparent and without some colors, maybe colorspace problem? ;( They seem good in the preview View but when I write them "something" happens. I wonder what it that.

-(void)savePNGImage:(CGImageRef)imageRef path:(NSString *)path {
    NSURL *outURL = [[NSURL alloc] initFileURLWithPath:path]; 
    CGImageDestinationRef dr = CGImageDestinationCreateWithURL ((CFURLRef)outURL, (CFStringRef)@"public.png" , 1, NULL);
    CGImageDestinationAddImage(dr, imageRef, NULL);
    CGImageDestinationFinalize(dr);
    [outURL release];
}
-(void)saveJPEGImage:(CGImageRef)imageRef path:(NSString *)path {
    CFMutableDictionaryRef mSaveMetaAndOpts = CFDictionaryCreateMutable(nil, 0,
                                                                    &kCFTypeDictionaryKeyCallBacks,  &kCFTypeDictionaryValueCallBacks);
    CFDictionarySetValue(mSaveMetaAndOpts, kCGImageDestinationLossyCompressionQuality, 
                         [NSNumber numberWithFloat:1.0]);   // set the compression quality here
    NSURL *outURL = [[NSURL alloc] initFileURLWithPath:path];
    CGImageDestinationRef dr = CGImageDestinationCreateWithURL ((CFURLRef)outURL, (CFStringRef)@"public.jpeg" , 1, NULL);
    CGImageDestinationAddImage(dr, imageRef, mSaveMetaAndOpts);
    CGImageDestinationFinalize(dr);
    [outURL release];
}


- (void)captureOutput:(QTCaptureOutput *)captureOutput 
  didOutputVideoFrame:(CVImageBufferRef)videoFrame 
     withSampleBuffer:(QTSampleBuffer *)sampleBuffer 
       fromConnection:(QTCaptureConnection *)connection{

    CVPixelBufferLockBaseAddress(videoFrame,0); 
    uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddress(videoFrame); 
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(videoFrame); 
    size_t width = CVPixelBufferGetWidth(videoFrame); 
    size_t height = CVPixelBufferGetHeight(videoFrame); 
    CVPixelBufferUnlockBaseAddress(videoFrame,0);

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 
    CGContextRef newContext = CGBitmapContextCreate(baseAddress, 
                                                        width, height, 8, 
                                                        bytesPerRow, 
                                                        colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst); 
        CGImageRef frame = CGBitmapContextCreateImage(newContext); 

    CGContextRelease(newContext); 
    CGColorSpaceRelease(colorSpace);

    [self savePNGImage:frame path:[NSString stringWithFormat:@"/Users/nacho4d/Desktop/framesCam/frame%003d.png", frameNum++]];
[self saveJPEGImage:frame path:[NSString stringWithFormat:@"/Users/nacho4d/Desktop/framesCam/frame%003d.jpeg", frameNum++]];

    CGImageRelease(frame);
}

Capturer attributes are just frame size and pixel format like so: [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32ARGB], (id)kCVPixelBufferPixelFormatTypeKey

Update:

I have tried with JPEG also and I get the same kind of image, like there are some channels lacking in the image and all written frames have a white background. (since JPEG does not allow transparence ??)

The original and the written (JPEG) one:

alt text alt text (I don't show the PNG since is transparent and is difficult to see in a browser)

Thanks in advance.

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3 回答 3

3

我不确定您的问题是什么,但这是我将图像保存到磁盘的方式。只需传入您从委托方法获得的 CVImageBufferRef,当然还有您自己的 URL,它应该可以正常工作。至少它对我有用。祝你好运!

-(void)saveImage:(CVImageBufferRef)image toURL:(NSURL*)url{

    NSCIImageRep *imageRep = [NSCIImageRep imageRepWithCIImage:[CIImage imageWithCVImageBuffer:image]];

    NSImage *_image = [[NSImage alloc] initWithSize:[imageRep size]];
    [_image addRepresentation:imageRep];

    NSData *bitmapData = [_image TIFFRep    resentation];
    NSBitmapImageRep *bitmapRep = [NSBitmapImageRep imageRepWithData:bitmapData];
    NSData *imageData = [bitmapRep representationUsingType:NSJPEGFileType properties:nil];

    [_image release];
    _image = [[NSImage alloc] initWithData:imageData];

    NSBitmapImageRep *imgRep = [[_image representations] objectAtIndex: 0];
    NSData *data = [imgRep representationUsingType: NSPNGFileType properties: nil];
    [data writeToFile: [self getSaveString] atomically: NO];

    [_image release];
}
于 2011-10-18T18:08:52.530 回答
1

我正在做一些类似的事情,并看到同样的问题。我稍微修改了您的代码,并更改kCGImageAlphaPremultipliedFirstkCGImageAlphaNoneSkipFirst. 大概是因为帧不包含 alpha,即使它是每像素 32 位,这为我解决了问题。

于 2014-01-25T02:11:05.227 回答
1

您在实际处理之前解锁图像缓冲区。尝试移动这条线:

CVPixelBufferUnlockBaseAddress(videoFrame,0);

到最后

于 2011-11-07T04:27:22.983 回答