UIImage from CMSampleBufferRef conversion, resulting UIImage not rendering properly - ios

Question

I am working with AV Foundation, i am attempting to save a particular
output CMSampleBufferRef as UIImage in some variable. i am using manatee works sample code and it uses
kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange for
kCVPixelBufferPixelFormatTypeKey
NSNumber* value = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange];
NSDictionary* videoSettings = [NSDictionary dictionaryWithObject:value forKey:key];
[captureOutput setVideoSettings:videoSettings];
but when i save the image, the output is just nil or whatever is the background of ImageView. I also tried not to set the output setting and just use whatever is the default but of no use. the image is still not rendered. i also tried to set kCVPixelFormatType_32BGRAbut then manatee works stops detecting bar code.
I am using the context settings from sample code provided by apple on developer website
// Create a bitmap graphics context with the sample buffer data
CGContextRef context = CGBitmapContextCreate(NULL,
CVPixelBufferGetWidth(imageBuffer),
CVPixelBufferGetHeight(imageBuffer),
8,
0,
CGColorSpaceCreateDeviceRGB(),
kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
// Create a Quartz image from the pixel data in the bitmap graphics context
CGImageRef quartzImage = CGBitmapContextCreateImage(context);
Can anybody help me on what is going wrong here? It should be simple but i don't have much of experience with AVFoundation Framework. Is this is some color space problem as the context is using CGColorSpaceCreateDeviceRGB() ?
I can provide more info if needed. I searched StackOverflow and there were many entries regarding this but none solved my problem

Answer 1

Is there a reason you are passing 0 for bytesPerRow to CGBitmapContextCreate?
Also, you are passing NULL as the buffer instead of the CMSampleBufferRef address.
Creating the bitmap context should look approximately like this when sampleBuffer is your CMSampleBufferRef:
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CVPixelBufferLockBaseAddress(imageBuffer,0);
uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddressOfPlane(imageBuffer, 0);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(baseAddress,
CVPixelBufferGetWidth(imageBuffer),
CVPixelBufferGetHeight(imageBuffer),
8,
CVPixelBufferGetBytesPerRow(imageBuffer),
colorSpace,
kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
// Create a Quartz image from the pixel data in the bitmap graphics context
CGImageRef quartzImage = CGBitmapContextCreateImage(context);
CGColorSpaceRelease(colorSpace);
CVPixelBufferUnlockBaseAddress(imageBuffer,0);
CGContextRelease(newContext);

Answer 2

Here is how I used to do it. The code is written in swift. But it works.
You should notice the orientation parameter at the last line, it depends on the video settings.
extension UIImage {
/**
Creates a new UIImage from the video frame sample buffer passed.
#param sampleBuffer the sample buffer to be converted into a UIImage.
*/
convenience init?(sampleBuffer: CMSampleBufferRef) {
// Get a CMSampleBuffer's Core Video image buffer for the media data
let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
// Lock the base address of the pixel buffer
CVPixelBufferLockBaseAddress(imageBuffer, 0)
// Get the number of bytes per row for the pixel buffer
let baseAddress = CVPixelBufferGetBaseAddress(imageBuffer)
// Get the number of bytes per row for the pixel buffer
let bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer)
// Get the pixel buffer width and height
let width = CVPixelBufferGetWidth(imageBuffer)
let height = CVPixelBufferGetHeight(imageBuffer)
// Create a device-dependent RGB color space
let colorSpace = CGColorSpaceCreateDeviceRGB()
// Create a bitmap graphics context with the sample buffer data
let bitmap = CGBitmapInfo(CGBitmapInfo.ByteOrder32Little.rawValue|CGImageAlphaInfo.PremultipliedFirst.rawValue)
let context = CGBitmapContextCreate(baseAddress, width, height, 8,
bytesPerRow, colorSpace, bitmap)
// Create a Quartz image from the pixel data in the bitmap graphics context
let quartzImage = CGBitmapContextCreateImage(context)
// Unlock the pixel buffer
CVPixelBufferUnlockBaseAddress(imageBuffer,0)
// Create an image object from the Quartz image
self.init(CGImage: quartzImage, scale: 1, orientation: UIImageOrientation.LeftMirrored)
}
}

Answer 3

I use this regularly:
UIImage *image = [UIImage imageWithData:[self imageToBuffer:sampleBuffer]];
- (NSData *) imageToBuffer:(CMSampleBufferRef)source {
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(source);
CVPixelBufferLockBaseAddress(imageBuffer,0);
size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
size_t width = CVPixelBufferGetWidth(imageBuffer);
size_t height = CVPixelBufferGetHeight(imageBuffer);
void *src_buff = CVPixelBufferGetBaseAddress(imageBuffer);
NSData *data = [NSData dataWithBytes:src_buff length:bytesPerRow * height];
CVPixelBufferUnlockBaseAddress(imageBuffer, 0);
return data;
}