gistfile1.m

-(UIImage*)image:(UIImage*)image scaleAndRotateImageToMaxResolution:(int)resolution
{
	int kMaxResolution = resolution; // 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, 0.0F);
			transform = CGAffineTransformScale(transform, -1.0F, 1.0F);
			break;

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

		case UIImageOrientationDownMirrored: //EXIF = 4
			transform = CGAffineTransformMakeTranslation(0.0F, imageSize.height);
			transform = CGAffineTransformScale(transform, 1.0F, -1.0F);
			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, -1.0F, 1.0F);
			transform = CGAffineTransformRotate(transform, 3.0F * (CGFloat)M_PI / 2.0F);
			break;

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

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

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