UIImage to CVPixelBufferRef empty - ios

Question

I am using this code to create CVPixelBufferRef:
NSDictionary *videoSettings = #{AVVideoCodecKey: AVVideoCodecH264,
AVVideoWidthKey: [NSNumber numberWithInt:size.width],
AVVideoHeightKey: [NSNumber numberWithInt:size.height]};
self.writerInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo
outputSettings:videoSettings];
self.adaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:self.writerInput sourcePixelBufferAttributes:nil];
CVPixelBufferRef buffer;
CVPixelBufferPoolCreatePixelBuffer(NULL, self.adaptor.pixelBufferPool, &buffer);
buffer = [self pixelBufferFromCGImage:[frame CGImage] size:self.videoSize];
this is the pixelBufferFromCGImage function:
+ (CVPixelBufferRef)pixelBufferFromCGImage:(CGImageRef)image
size:(CGSize)imageSize
{
NSDictionary *options = #{(id)kCVPixelBufferCGImageCompatibilityKey: #YES,
(id)kCVPixelBufferCGBitmapContextCompatibilityKey: #YES};
CVPixelBufferRef pxbuffer = NULL;
CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, imageSize.width,
imageSize.height, kCVPixelFormatType_32ARGB, (__bridge CFDictionaryRef) options,
&pxbuffer);
NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL);
CVPixelBufferLockBaseAddress(pxbuffer, 0);
void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer);
NSParameterAssert(pxdata != NULL);
CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(pxdata, imageSize.width,
imageSize.height, 8, 4*imageSize.width, rgbColorSpace,
kCGImageAlphaNoneSkipFirst);
NSParameterAssert(context);
CGContextDrawImage(context, CGRectMake(0 + (imageSize.width-CGImageGetWidth(image))/2,
(imageSize.height-CGImageGetHeight(image))/2,
CGImageGetWidth(image),
CGImageGetHeight(image)), image);
CGColorSpaceRelease(rgbColorSpace);
CGContextRelease(context);
CVPixelBufferUnlockBaseAddress(pxbuffer, 0);
return pxbuffer;
}
The problem is that the buffer is allways empty, any idea why its happen?

Answer 1

I guess that the buffer is always nil because the "videoSize" is not valid. I have tested your code in 3 scenarios and here is the results
The first one I passed valid parameters with an image and size 200x200. The buffer was not nil.
The second one I passed a nil for image and video size 200x200. The buffer was not nil.
The last one I passed a valid image but invalid video size 0x0 and the buffer was nil. The return status is
kCVReturnInvalidArgument
Invalid function parameter. For example, out of range or the wrong type.
Value
-6661
Description
Invalid function parameter. For example, out of range or the wrong type.
Hope this will help you.
This is the code that I tested.
- (void)viewDidLoad
{
[super viewDidLoad];
UIImage *image = [UIImage imageNamed:#"Doge-Meme.jpg"];
CVPixelBufferRef bufferRef = [[self class] pixelBufferFromCGImage:image.CGImage size:CGSizeMake(200, 200)];
NSLog(#"## %#", bufferRef);//not nil
CVPixelBufferRef bufferRef1 = [[self class] pixelBufferFromCGImage:nil size:CGSizeMake(200, 200)];
NSLog(#"## %#", bufferRef1);//not nil
CVPixelBufferRef bufferRef2 = [[self class] pixelBufferFromCGImage:image.CGImage size:CGSizeMake(0, 0)];
NSLog(#"## %#", bufferRef2);//nil
}
+ (CVPixelBufferRef)pixelBufferFromCGImage:(CGImageRef)image
size:(CGSize)imageSize
{
NSDictionary *options = #{(id)kCVPixelBufferCGImageCompatibilityKey: #YES,
(id)kCVPixelBufferCGBitmapContextCompatibilityKey: #YES};
CVPixelBufferRef pxbuffer = NULL;
CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, imageSize.width,
imageSize.height, kCVPixelFormatType_32ARGB, (__bridge CFDictionaryRef) options,
&pxbuffer);
NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL);
CVPixelBufferLockBaseAddress(pxbuffer, 0);
void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer);
NSParameterAssert(pxdata != NULL);
CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(pxdata, imageSize.width,
imageSize.height, 8, 4*imageSize.width, rgbColorSpace,
kCGImageAlphaNoneSkipFirst);
NSParameterAssert(context);
CGContextDrawImage(context, CGRectMake(0 + (imageSize.width-CGImageGetWidth(image))/2,
(imageSize.height-CGImageGetHeight(image))/2,
CGImageGetWidth(image),
CGImageGetHeight(image)), image);
CGColorSpaceRelease(rgbColorSpace);
CGContextRelease(context);
CVPixelBufferUnlockBaseAddress(pxbuffer, 0);
return pxbuffer;
}