Error With CBitmapContextCreate, CGContextDrawImage, CGBitmapContextCreateImage

Question

Error: CGBitmapContextCreate: invalid data bytes/row: should be at least 400 for 8 integer bits/component, 3 components, kCGImageAlphaNoneSkipFirst.

Error: CGContextDrawImage: invalid context

Error: CGBitmapContextCreateImage: invalid context

Currently, I have in application that runs perfectly in OS 4.0, but I have been trying to get it to work properly in 3.1.3 and I keep getting the errors mentioned above.

I am fairly new to iPhone development and am not exactly sure what the problem would be. I am using image resize code that I found in another post on stackoverflow.

Here is the code:

- (UIImage*)imageWithImage:(UIImage*)sourceImage scaledToSizeWithSameAspectRatio:(CGSize)targetSize{  
CGSize imageSize = sourceImage.size;
CGFloat width = imageSize.width;
CGFloat height = imageSize.height;
CGFloat targetWidth = targetSize.width;
CGFloat targetHeight = targetSize.height;
CGFloat scaleFactor = 0.0;
CGFloat scaledWidth = targetWidth;
CGFloat scaledHeight = targetHeight;
CGPoint thumbnailPoint = CGPointMake(0.0,0.0);

if (CGSizeEqualToSize(imageSize, targetSize) == NO) {
    CGFloat widthFactor = targetWidth / width;
    CGFloat heightFactor = targetHeight / height;

    if (widthFactor > heightFactor) {
        scaleFactor = widthFactor; // scale to fit height
    }
    else {
        scaleFactor = heightFactor; // scale to fit width
    }

    scaledWidth  = width * scaleFactor;
    scaledHeight = height * scaleFactor;

    // center the image
    if (widthFactor > heightFactor) {
        thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5; 
    }
    else if (widthFactor < heightFactor) {
        thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
    }
}     

CGImageRef imageRef = [sourceImage CGImage];
CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
CGColorSpaceRef colorSpaceInfo = CGImageGetColorSpace(imageRef);

if (bitmapInfo == kCGImageAlphaNone) {
    bitmapInfo = kCGImageAlphaNoneSkipLast;
}

CGContextRef bitmap;

if (sourceImage.imageOrientation == UIImageOrientationUp || sourceImage.imageOrientation == UIImageOrientationDown) {
    bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);

} else {
    bitmap = CGBitmapContextCreate(NULL, targetHeight, targetWidth, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);

}       

// In the right or left cases, we need to switch scaledWidth and scaledHeight,
// and also the thumbnail point
if (sourceImage.imageOrientation == UIImageOrientationLeft) {
    thumbnailPoint = CGPointMake(thumbnailPoint.y, thumbnailPoint.x);
    CGFloat oldScaledWidth = scaledWidth;
    scaledWidth = scaledHeight;
    scaledHeight = oldScaledWidth;

    CGContextRotateCTM (bitmap, radians(90));
    CGContextTranslateCTM (bitmap, 0, -targetHeight);

} else if (sourceImage.imageOrientation == UIImageOrientationRight) {
    thumbnailPoint = CGPointMake(thumbnailPoint.y, thumbnailPoint.x);
    CGFloat oldScaledWidth = scaledWidth;
    scaledWidth = scaledHeight;
    scaledHeight = oldScaledWidth;

    CGContextRotateCTM (bitmap, radians(-90));
    CGContextTranslateCTM (bitmap, -targetWidth, 0);

} else if (sourceImage.imageOrientation == UIImageOrientationUp) {
    // NOTHING
} else if (sourceImage.imageOrientation == UIImageOrientationDown) {
    CGContextTranslateCTM (bitmap, targetWidth, targetHeight);
    CGContextRotateCTM (bitmap, radians(-180.));
}

CGContextDrawImage(bitmap, CGRectMake(thumbnailPoint.x, thumbnailPoint.y, scaledWidth, scaledHeight), imageRef);
CGImageRef ref = CGBitmapContextCreateImage(bitmap);
UIImage* newImage = [UIImage imageWithCGImage:ref];

CGContextRelease(bitmap);
CGImageRelease(ref);

return newImage; 

Any help would be appreciated. If you need more info, I will gladly post it.

Answer 1

The first error is telling you that it is incorrect to pass CGImageGetBitsPerComponent(imageRef) as the row bytes of the new bitmap context. The row byte count needs to be at least the width times the number of bytes per pixel.