CGBitmapContext byte order changed to ABGR - and CGImage metadata doesn't seem to match bitmap contents

Question

I am standardizing the orientation and max size of an image using the following code (gleaned from elsewhere):

+ (UIImage *)scaleAndRotateImage:(UIImage *)image
{
    int kMaxResolution = 960; // Or whatever

    CGImageRef imgRef = image.CGImage;

    CGFloat width = CGImageGetWidth(imgRef);
    CGFloat height = CGImageGetHeight(imgRef);

    CGAffineTransform transform = CGAffineTransformIdentity;
    CGRect bounds = CGRectMake(0, 0, width, height);
    if (width > kMaxResolution || height > kMaxResolution) {
        CGFloat ratio = width/height;
        if (ratio > 1) {
            bounds.size.width = kMaxResolution;
            bounds.size.height = bounds.size.width / ratio;
        }
        else {
            bounds.size.height = kMaxResolution;
            bounds.size.width = bounds.size.height * ratio;
        }
    }

    CGFloat scaleRatio = bounds.size.width / width;
    CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));
    CGFloat boundHeight;
    UIImageOrientation orient = image.imageOrientation;
    switch(orient) {

        case UIImageOrientationUp: //EXIF = 1
            transform = CGAffineTransformIdentity;
            break;

        case UIImageOrientationUpMirrored: //EXIF = 2
            transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0);
            transform = CGAffineTransformScale(transform, -1.0, 1.0);
            break;

        case UIImageOrientationDown: //EXIF = 3
            transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height);
            transform = CGAffineTransformRotate(transform, M_PI);
            break;

        case UIImageOrientationDownMirrored: //EXIF = 4
            transform = CGAffineTransformMakeTranslation(0.0, imageSize.height);
            transform = CGAffineTransformScale(transform, 1.0, -1.0);
            break;

        case UIImageOrientationLeftMirrored: //EXIF = 5
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width);
            transform = CGAffineTransformScale(transform, -1.0, 1.0);
            transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
            break;

        case UIImageOrientationLeft: //EXIF = 6
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(0.0, imageSize.width);
            transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
            break;

        case UIImageOrientationRightMirrored: //EXIF = 7
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeScale(-1.0, 1.0);
            transform = CGAffineTransformRotate(transform, M_PI / 2.0);
            break;

        case UIImageOrientationRight: //EXIF = 8
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0);
            transform = CGAffineTransformRotate(transform, M_PI / 2.0);
            break;

        default:
            [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];

    }

    UIGraphicsBeginImageContext(bounds.size);

    CGContextRef context = UIGraphicsGetCurrentContext();

    if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) {
        CGContextScaleCTM(context, -scaleRatio, scaleRatio);
        CGContextTranslateCTM(context, -height, 0);
    }
    else {
        CGContextScaleCTM(context, scaleRatio, -scaleRatio);
        CGContextTranslateCTM(context, 0, -height);
    }

    CGContextConcatCTM(context, transform);

    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);
    UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();


    return imageCopy;

}

This code correctly returns a UIImage with rotation converted to UIImageOrientationUp and image possibly scaled down if it exceeded the max image size. This code works fine for displaying the UIImage in a UIView.

However my problem arises on the next step if I take that new UIImage and extract its CGImage contents into a bitmap context.

CGImageRef inImage = inputImage.CGImage;

// create data object for direct pixel manipulation
CFDataRef m_DataRef;
    m_DataRef = CGDataProviderCopyData(CGImageGetDataProvider(inImage));
    UInt8 * m_PixelBuf = (UInt8 *) CFDataGetBytePtr(m_DataRef);

//create initial context for drawing on the eyelids
CGContextRef ctx = CGBitmapContextCreate(m_PixelBuf,
                                         CGImageGetWidth( inImage ),
                                         CGImageGetHeight( inImage ),
                                         8,
                                         CGImageGetBytesPerRow( inImage ),
                                         CGImageGetColorSpace( inImage ),
                                         CGImageGetAlphaInfo( inImage ) );

And then convert it back to a UIImage all the colors are wrong. I checked the CGImageGetAlphaInfo it was getting from inImage to setup the context which was set to kCGImageAlphaPremultipliedFirst and if I forced AlphaInfo to be kCGImageAlphaPremultipliedLast I could at least see the image, but red was obviously showing as blue. Finally I found RGBA data in the bitmap has been transposed to ABGR, and by creating a loop to transpose the byte order back to RGBA I found I could again re-create a correct UIImage using the context created from the CGImage.

Only when I pass through scale and rotate method I do have this ABGR problem. My understanding is that I should be able to convert a UIImage to a CGbitmapContext and back again using its own metadata as context parameters to receive exactly the same image.

My questions are: Why is the bitmap pixel byte order changed to ABGR? How has the CGImage metadata become messed up that that I cant recreate a CGImage directly from a BitmapContext created from itself?

Thanks in advance!