QCAR::Image to UIImage - CoreGraphics and retain crash

Question

I'm using Vuforia , trying to get pixels from camera instance and convert to UIImage

- (UIImage *)createUIImage:(const QCAR::Image *)qcarImage
{
    int width = qcarImage->getWidth();
    int height = qcarImage->getHeight();
    int bitsPerComponent = 8;
    int bitsPerPixel = QCAR::getBitsPerPixel(QCAR::RGB888);
    int bytesPerRow = qcarImage->getBufferWidth() * bitsPerPixel / bitsPerComponent;
    CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
    CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault | kCGImageAlphaNone;
    CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;

    CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, qcarImage->getPixels(), QCAR::getBufferSize(width, height, QCAR::RGB888), NULL);

    CGImageRef imageRef = CGImageCreate(width, height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
    CGImageRef imageRefRetain = CGImageRetain(imageRef);
    UIImage *image = [UIImage imageWithCGImage:imageRefRetain];

    CGDataProviderRelease(provider);
    CGColorSpaceRelease(colorSpaceRef);
    CGImageRelease(imageRef);

    return image;
}

After getting the image, I add it to a mutable array.

Once retrieving the image from the mutable array, I get crash on every method i.e.

UIImageView setImage: 

or even calling

NSData* comppressedData = UIImageJPEGRepresentation(image,1);

The only way to make my app not to crash is adding the following

- (UIImage *)createUIImage:(const QCAR::Image *)qcarImage
{
    ...
    UIImage *image = [UIImage imageWithCGImage:imageRefRetain];

    CGDataProviderRelease(provider);
    CGColorSpaceRelease(colorSpaceRef);
    CGImageRelease(imageRef);

    NSData* comppressedData = UIImageJPEGRepresentation(image,1);
                    UIImage* jpegImage = [UIImage imageWithData:comppressedData];
    return jpegImage;
}

So i think it's an issue related to the CGImageRef getting released. I really need to understand what's going on and why the image ref isn't valid after existing the method.

Answer 1

The problem is that the qcarImage is going out of scope and taking the raw image data with it. Copy the image buffer and provide that to the CGDataProviderRef

NSData * imageData = [NSData dataWithBytes:qcarImage->getPixels() 
                                    length:QCAR::getBufferSize(width, height, QCAR::RGB888)];
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, imageData.bytes, imageData.length, NULL);
CGImageRef imageRef = CGImageCreate(width, height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
//This was leaking memory, commenting out
//CGImageRef imageRefRetain = CGImageRetain(imageRef);
UIImage *image = [UIImage imageWithCGImage:imageRef];