http://www.iphonedevsdk.com/forum/iphone-sdk-development/7307-resizing-photo-new-uiimage.html

Resizing UIImage

-(UIImage*)imageByScalingToSize:(CGSize)targetSize
{
	UIImage* sourceImage = self; 
	CGFloat targetWidth = targetSize.width;
	CGFloat targetHeight = targetSize.height;
		
	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) {
		CGContextRotateCTM (bitmap, radians(90));
		CGContextTranslateCTM (bitmap, 0, -targetHeight);
		
	} else if (sourceImage.imageOrientation == UIImageOrientationRight) {
		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(0, 0, targetWidth, targetHeight), imageRef);
	CGImageRef ref = CGBitmapContextCreateImage(bitmap);
	UIImage* newImage = [UIImage imageWithCGImage:ref];
	
	CGContextRelease(bitmap);
	CGImageRelease(ref);
	
	return newImage; 
}