iPhone CGContextRef CGBitmapContextCreate unsupported parameter combination

Question

In my application I need to resize and crop some images, stored locally and online. I am using Trevor Harmon's tutorial which implements UIImage+Resize.

On my iPhone 4(iOS 4.3.1) everything works OK, I have no problems. But on my iPhone 3G (iOS 3.2) the resizing and crop methods are not working for any picture (the locally stored ones are PNGs). This is the console output:

Tue Apr  5 02:34:44 Andreis-MacBook-Pro.local Puzzle[12453] <Error>: CGBitmapContextCreate:     unsupported parameter combination: 8 integer bits/component; 32 bits/pixel; 3-component color space; kCGImageAlphaLast; 288 bytes/row.
Tue Apr  5 02:34:44 Andreis-MacBook-Pro.local Puzzle[12453] <Error>: CGBitmapContextCreate: unsupported parameter combination: 8 integer bits/component; 32 bits/pixel; 3-component color space; kCGImageAlphaLast; 288 bytes/row.
Tue Apr  5 02:34:44 Andreis-MacBook-Pro.local Puzzle[12453] <Error>: CGBitmapContextCreate: unsupported parameter combination: 8 integer bits/component; 32 bits/pixel; 3-component color space; kCGImageAlphaLast; 288 bytes/row.
Tue Apr  5 02:34:44 Andreis-MacBook-Pro.local Puzzle[12453] <Error>: CGBitmapContextCreate: unsupported parameter combination: 8 integer bits/component; 32 bits/pixel; 3-component color space; kCGImageAlphaLast; 288 bytes/row.

This is the crop method

- (UIImage *)croppedImage:(CGRect)bounds 
{
    CGImageRef imageRef = CGImageCreateWithImageInRect([self CGImage], bounds);
    UIImage *croppedImage = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    return croppedImage;
}

The resize method is this:

- (UIImage *)resizedImage:(CGSize)newSize
            transform:(CGAffineTransform)transform
       drawTransposed:(BOOL)transpose
 interpolationQuality:(CGInterpolationQuality)quality 
{
    CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height));
    CGRect transposedRect = CGRectMake(0, 0, newRect.size.height, newRect.size.width);
    CGImageRef imageRef = self.CGImage;

    CGContextRef bitmap = CGBitmapContextCreate(NULL,
                                            newRect.size.width,
                                            newRect.size.height,
                                            CGImageGetBitsPerComponent(imageRef),
                                            0,
                                            CGImageGetColorSpace(imageRef),
                                            CGImageGetBitmapInfo(imageRef));
    if(bitmap == nil)
        return nil;

    CGContextConcatCTM(bitmap, transform);

    CGContextSetInterpolationQuality(bitmap, quality);

    CGContextDrawImage(bitmap, transpose ? transposedRect : newRect, imageRef);

    CGImageRef newImageRef = CGBitmapContextCreateImage(bitmap);
    UIImage *newImage = [UIImage imageWithCGImage:newImageRef];

    CGContextRelease(bitmap);
    CGImageRelease(newImageRef);

    return newImage;
}

Can someone explain to me way I have this issue?

Thank you, Andrei

Answer 1

Replying here since I had the exact same pixel format when I got this error. I hope this answer helps someone.

The reason it was failing, in my case, was that kCGImageAlphaLast isn't a permitted value anymore on iOS 8, although it works well on iOS 7. The 32 pbb, 8 bpc combination only allows kCGImageAlphaNoneSkip* and kCGImageAlphaPremultiplied* for the Alpha Info. Apparently this was a problem always, but wasn't enforced before iOS 8. Here's my solution:

- (CGBitmapInfo)normalizeBitmapInfo:(CGBitmapInfo)oldBitmapInfo {
    //extract the alpha info by resetting everything else
    CGImageAlphaInfo alphaInfo = oldBitmapInfo & kCGBitmapAlphaInfoMask;

    //Since iOS8 it's not allowed anymore to create contexts with unmultiplied Alpha info
    if (alphaInfo == kCGImageAlphaLast) {
        alphaInfo = kCGImageAlphaPremultipliedLast;
    }
    if (alphaInfo == kCGImageAlphaFirst) {
        alphaInfo = kCGImageAlphaPremultipliedFirst;
    }

    //reset the bits
    CGBitmapInfo newBitmapInfo = oldBitmapInfo & ~kCGBitmapAlphaInfoMask;

    //set the bits to the new alphaInfo
    newBitmapInfo |= alphaInfo;

    return newBitmapInfo;
}

In my case the failing piece of code looked like this, where imageRef is a CGImageRef of a PNG loaded from the app bundle:

CGContextRef bitmap = CGBitmapContextCreate(NULL,
                                                newRect.size.width,
                                                newRect.size.height,
                                                CGImageGetBitsPerComponent(imageRef),
                                                0,
                                                CGImageGetColorSpace(imageRef),
                                                CGImageGetBitmapInfo(imageRef));

Sources: https://stackoverflow.com/a/19345325/3099609

https://developer.apple.com/library/mac/DOCUMENTATION/GraphicsImaging/Conceptual/drawingwithquartz2d/dq_context/dq_context.html#//apple_ref/doc/uid/TP30001066-CH203-BCIBHHBB