I have CMSampleBufferRef(s) which I decode using VTDecompressionSessionDecodeFrame which results in CVImageBufferRef after decoding of a frame has completed, so my questions is..
What would be the most efficient way to display these CVImageBufferRefs in UIView?
I have succeeded in converting CVImageBufferRef to CGImageRef and displaying those by settings CGImageRef as CALayer's content but then DecompressionSession has been configured with #{ (id)kCVPixelBufferPixelFormatTypeKey: [NSNumber numberWithInt:kCVPixelFormatType_32BGRA] };
Here is example/code how I've converted CVImageBufferRef to CGImageRef (note: cvpixelbuffer data has to be in 32BGRA format for this to work)
CVPixelBufferLockBaseAddress(cvImageBuffer,0);
// get image properties
uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddress(cvImageBuffer);
size_t bytesPerRow = CVPixelBufferGetBytesPerRow(cvImageBuffer);
size_t width = CVPixelBufferGetWidth(cvImageBuffer);
size_t height = CVPixelBufferGetHeight(cvImageBuffer);
/*Create a CGImageRef from the CVImageBufferRef*/
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef cgContext = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
CGImageRef cgImage = CGBitmapContextCreateImage(cgContext);
// release context and colorspace
CGContextRelease(cgContext);
CGColorSpaceRelease(colorSpace);
// now CGImageRef can be displayed either by setting CALayer content
// or by creating a [UIImage withCGImage:geImage] that can be displayed on
// UIImageView ...
The #WWDC14 session 513 (https://developer.apple.com/videos/wwdc/2014/#513) hints that YUV -> RGB colorspace conversion (using CPU?) can be avoided and if YUV capable GLES magic is used - wonder what that might be and how this could be accomplished?
Apple's iOS SampleCode GLCameraRipple shows an example of displaying YUV CVPixelBufferRef captured from camera using 2 OpenGLES with separate textures for Y and UV components and a fragment shader program that does the YUV to RGB colorspace conversion calculations using GPU - is all that really required, or is there some more straightforward way how this can be done?
NOTE: In my use case I'm unable to use AVSampleBufferDisplayLayer, due to fact how the input to decompression becomes available.
Update: The original answer below does not work because kCVPixelBufferIOSurfaceCoreAnimationCompatibilityKey is unavailable for iOS.
UIView is backed by a CALayer whose contents property supports multiple types of images. As detailed in my answer to a similar question for macOS, it is possible to use CALayer to render a CVPixelBuffer’s backing IOSurface. (Caveat: I have only tested this on macOS.)
If you're getting your CVImageBufferRef from CMSampleBufferRef, which you're receiving from captureOutput:didOutputSampleBuffer:fromConnection:, you don't need to make that conversion and can directly get the imageData out of CMSampleBufferRef. Here's the code:
NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:sampleBuffer];
UIImage *frameImage = [UIImage imageWithData:imageData];
API description doesn't provide any info about wether its 32BGRA supported or not, and produces imageData, along with any meta-data, in jpeg format without any compression applied. If your goal is to display the image on screen or use with UIImageView, this is the quick way.
Related
How do we fix our code below to properly color the image you see below from our incoming sampleBuffer?
We are attempting to convert an incoming sampleBuffer image to a UIImage but the result is the inverted off-color image you see below.
You can see our attempt to use the kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange option in the code - but the results were the same.
The incoming image we are trying to show has all the right colors as evidenced by the fact that if we render the image into a GLKView, all the colors are there.
Could this be a YUV420 conversion issue?
Here is the conversion code we are using:
- (CGImageRef) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer // Create a CGImageRef from sample buffer data
{
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CVPixelBufferLockBaseAddress(imageBuffer,0); // Lock the image buffer
uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddressOfPlane(imageBuffer, 0); // Get information of the image
size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
size_t width = CVPixelBufferGetWidth(imageBuffer);
size_t height = CVPixelBufferGetHeight(imageBuffer);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
// CGContextRef newContext = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
CGContextRef newContext = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange | kCGImageAlphaPremultipliedFirst);
CGImageRef newImage = CGBitmapContextCreateImage(newContext);
CGContextRelease(newContext);
CGColorSpaceRelease(colorSpace);
CVPixelBufferUnlockBaseAddress(imageBuffer,0);
/* CVBufferRelease(imageBuffer); */ // do not call this!
return newImage;
}
Here is the setup code we use for the incoming CVPixelBuffer:
// Now create the CVPixelBuffer to which we will render
CVReturn retVal = CVPixelBufferCreate(kCFAllocatorDefault,
self.screenWidth,
self.screenHeight,
kCVPixelFormatType_32BGRA,
attrs,
&_outputRenderTarget);
Any suggestions for what to try to restore and display all the proper colors?
There is no problem with the code shown apart from you need to swap back your commented/uncommented lines.
I would take a step back and look at what is writing the data to your incoming buffer. For example I use a AVAssetReaderVideoCompositionOutput object to generate the sample buffers. The initialisation of the video composition object has video settings that match the ones you use for creating your incoming cvpixelbuffer plus a cgimage and bitmap compatibility key.
It turns out we were inverting all the colors with a 1-r, 1-g, 1-b.
Once we removed the inversion the colors appeared normal again.
I would like to get a data array containing the RGB representation of a picture stored in the photo library (an ALAsset) on iOS (ios8 sdk).
I already tried this method :
get the a CGImage from ALAsset with [ALAssetRepresentation fullScreenImage]
draw the CGImage to a CGContext.
That method works, I get a pointer to rgb data, but this is really slow (there are 2 conversions). The final goal is to load the image quickly in a OpenGL texture.
My code to get an image from Photo library
ALAsset* currentPhotoAsset = (ALAsset*) [self.photoAssetList objectAtIndex:_currentPhotoAssetIndex];
ALAssetRepresentation *representation = [currentPhotoAsset defaultRepresentation];
//-> REALLY SLOW
UIImage *currentPhoto = [UIImage imageWithCGImage:[representation fullScreenImage]];
My code to draw on the CGContext :
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * textureWidth;
NSUInteger bitsPerComponent = 8;
CGContextRef context = CGBitmapContextCreate(textureData, textureWidth, textureHeight,
bitsPerComponent, bytesPerRow, colorSpace,
kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);
//--> THAT'S REALLY SLOW
CGContextDrawImage(context, CGRectMake(0, 0, textureWidth, textureHeight), cgimage);
CGContextRelease(context);
There is not much you can do but I if you find a way I would be happy to hear about it.
The thing is you need to decompress the image (jpg, png...) which is usually done by creating a CGImage (UIImage is just a wrapper around it). But then you are not allowed to get the data pointer directly from the CGImage but you need to copy them (the really slow draw call). Though then again if the target size and format are the same as the source this operation should be quite fast since the data should more or less simply be copied. On the other hand if your textureWidth and textureHeight are different then the image dimensions those pixels need to be interpolated and this function can become even a few times slower.
The only way out of this I see is to get some library to directly decompress the image from file and get the data pointer of that image. But I never had a performance issue for loading image textures (use a background thread).
Anyway if you are not doing something similar already how I use this is to get the image size, then find the POT (power of two) width and height that fills the image size. Then I create an empty texture with those POT dimensions and call sub image to pass the original image data to the texture. I use a custom texture class to handle this which also contains (generates) texture coordinates so the correct part of the texture is drawn to the frame buffer. Then this class is extended to support atlasing which is generally what you want to do when dealing with many images (textures).
I hope this info helps you in any way...
I have an 2D array of RGB values (or any such data container) that I need to write to UIView that is currently displayed to the user. An example would be — while using the capture output from the camera, I run some algorithms to identify objects and then highlight them using custom defined RGB pixels.
What is the best way to do this as this whole thing is done in real-time every 10 frames per second for example?
Use the method below to create a UIImage from your 2D array. You can then display this image using a UIImageView.
-(UIImage *)imageFromArray:(void *)array width:(unsigned int)width height:(unsigned int)height {
/*
Assuming pixel color values are 8 bit unsigned
You need to create an array that is in the format BGRA (blue,green,red,alpha).
You can achieve this by implementing a for-loop that sets the values at each index.
I have not included a for-loop in this example because it depends on how the values are stored in your input 2D array.
You can set the alpha value to 255.
*/
unsigned char pixelData[width * height * 4];
// This is where the for-loop would be
void *baseAddress = &pixelData;
size_t bytesPerRow = width * 4;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
CGImageRef cgImage = CGBitmapContextCreateImage(context);
UIImage *image = [UIImage imageWithCGImage:cgImage];
CGImageRelease(cgImage);
CGColorSpaceRelease(colorSpace);
CGContextRelease(context);
return image;
}
I'm working with AVCaptureVideoDataOutput and want to convert CMSampleBufferRef to UIImage. Many answers are the same, like this UIImage created from CMSampleBufferRef not displayed in UIImageView? and AVCaptureSession with multiple previews
It works fine if I set the VideoDataOutput color space to BGRA (credited to this answer CGBitmapContextCreateImage error)
NSString* key = (NSString*)kCVPixelBufferPixelFormatTypeKey;
NSNumber* value = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA];
NSDictionary* videoSettings = [NSDictionary dictionaryWithObject:value forKey:key];
[dataOutput setVideoSettings:videoSettings];
Without the above videoSettings, I will receive the following errors
CGBitmapContextCreate: invalid data bytes/row: should be at least 2560 for 8 integer bits/component, 3 components, kCGImageAlphaPremultipliedFirst.
<Error>: CGBitmapContextCreateImage: invalid context 0x0
Working with BGRA is not a good choice, since there is conversion overhead from YUV (default AVCaptureSession color space) to BGRA, as stated by Brad and Codo in How to get the Y component from CMSampleBuffer resulted from the AVCaptureSession?
So is there a way to convert CMSampleBufferRef to UIImage and working with YUV color space ?
After doing a lots of research and read apple documentations and wikipedis. I figured out the answer and it is works perfectly for me. So for the future readers Im sharing the code to convert CMSampleBufferRef to UIImage when video pixel type is set as kCVPixelFormatType_420YpCbCr8BiPlanarFullRange
// Create a UIImage from sample buffer data
// Works only if pixel format is kCVPixelFormatType_420YpCbCr8BiPlanarFullRange
-(UIImage *) imageFromSamplePlanerPixelBuffer:(CMSampleBufferRef) sampleBuffer{
#autoreleasepool {
// Get a CMSampleBuffer's Core Video image buffer for the media data
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
// Lock the base address of the pixel buffer
CVPixelBufferLockBaseAddress(imageBuffer, 0);
// Get the number of bytes per row for the plane pixel buffer
void *baseAddress = CVPixelBufferGetBaseAddressOfPlane(imageBuffer, 0);
// Get the number of bytes per row for the plane pixel buffer
size_t bytesPerRow = CVPixelBufferGetBytesPerRowOfPlane(imageBuffer,0);
// Get the pixel buffer width and height
size_t width = CVPixelBufferGetWidth(imageBuffer);
size_t height = CVPixelBufferGetHeight(imageBuffer);
// Create a device-dependent gray color space
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
// Create a bitmap graphics context with the sample buffer data
CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8,
bytesPerRow, colorSpace, kCGImageAlphaNone);
// Create a Quartz image from the pixel data in the bitmap graphics context
CGImageRef quartzImage = CGBitmapContextCreateImage(context);
// Unlock the pixel buffer
CVPixelBufferUnlockBaseAddress(imageBuffer,0);
// Free up the context and color space
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
// Create an image object from the Quartz image
UIImage *image = [UIImage imageWithCGImage:quartzImage];
// Release the Quartz image
CGImageRelease(quartzImage);
return (image);
}
}
// it works for me.
var image: CGImage?
VTCreateCGImageFromCVPixelBuffer(pixelBuffer, options: nil, imageOut: &image)
DispatchQueue.main.async {
self.imageView.image = UIImage(cgImage: image!)
}
I'm using this well known sample code from Apple to convert camera buffer still images into UIImages.
-(UIImage*) getUIImageFromBuffer:(CMSampleBufferRef) imageSampleBuffer{
// Get a CMSampleBuffer's Core Video image buffer for the media data
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(imageSampleBuffer);
if (imageBuffer==NULL) {
NSLog(#"No buffer");
}
// Lock the base address of the pixel buffer
if((CVPixelBufferLockBaseAddress(imageBuffer, 0))==kCVReturnSuccess){
NSLog(#"Buffer locked successfully");
}
void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);
// Get the number of bytes per row for the pixel buffer
size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
NSLog(#"bytes per row %zu",bytesPerRow );
// Get the pixel buffer width and height
size_t width = CVPixelBufferGetWidth(imageBuffer);
NSLog(#"width %zu",width);
size_t height = CVPixelBufferGetHeight(imageBuffer);
NSLog(#"height %zu",height);
// Create a device-dependent RGB color space
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
// Create a bitmap graphics context with the sample buffer data
CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8,
bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
// Create a Quartz image from the pixel data in the bitmap graphics context
CGImageRef quartzImage = CGBitmapContextCreateImage(context);
// Free up the context and color space
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
// Create an image object from the Quartz image
UIImage *image= [UIImage imageWithCGImage:quartzImage scale:SCALE_IMAGE_RATIO orientation:UIImageOrientationRight];
// Release the Quartz image
CGImageRelease(quartzImage);
// Unlock the pixel buffer
CVPixelBufferUnlockBaseAddress(imageBuffer,0);
return (image );}
The problem is that usually the image that you obtain is 90° rotated. Using the method +imageWithCGImage:scale:orientation I'm able to rotate it, but before getting into this method I was trying to rotate and scale the image using the CTM function, before passing it to a UIImage. the problem was that CTM transformation didn't affect the image.
I'm asking myself why... is that because I'm locking the buffer? or because the context is created with the image inside, so the changes will affect only the further mod?
Thank you
The answer is that it affects only further modifications, and it has nothing to deal with the buffer locking.
As you can read from this answer mod to the context are applied by time Vertical flip of CGContext