Draw UIImage with transformations in iOS - iphone

Question

I have some transformable UIImageViews (decorates on a photo), which user can drag, pinch and rotate. After editing, I want the app to generate the final image. How can I draw the UIImageViews with their transform property considered.
My first solution is using renderInContext, but it can only generate a 320x480 image. Can I generate an image with any resolution?
Then I use code as follows:
UIGraphicsBeginImageContext(CGSizeMake(640.0f, 896.0f));
CGContextRef currentContext = UIGraphicsGetCurrentContext();
UIImage *backgroundImage = [[UIImage alloc] initWithContentsOfFile:[[NSBundle mainBundle] pathForResource:#"fittingBackground" ofType:#"jpg"]];
[backgroundImage drawInRect:CGRectMake(0.0f, 0.0f, 640.0f, 896.0f)];
CGContextSaveGState(currentContext);
CGContextConcatCTM(currentContext, self.photoImageView.transform);
CGRect photoFrame = self.photoImageView.frame;
[self.photoImageView.image drawInRect:CGRectMake(photoFrame.origin.x * 2, photoFrame.origin.y * 2, photoFrame.size.width * 2, photoFrame.size.height * 2)];
CGContextRestoreGState(currentContext);
CGContextSaveGState(currentContext);
CGContextConcatCTM(currentContext, self.productImageView.transform);
CGRect productFrame = self.productImageView.frame;
[self.productImageView.image drawInRect:CGRectMake(productFrame.origin.x * 2, productFrame.origin.y * 2, productFrame.size.width * 2, productFrame.size.height * 2)];
CGContextRestoreGState(currentContext);
UIImage *resultImage = [UIImage imageWithCGImage:CGBitmapContextCreateImage(currentContext)];
UIGraphicsEndImageContext();
However, the result seems to be weird. And I've logged the frame, bounds and center. I don't know which Rect should I use in drawInRect after applying transform?

Answer 1

Try this,
-(void)drawBackgroundInLayer:(CALayer*)destinationLayer {
CGFloat scaledFactor = [[UIScreen mainScreen] scale];
CGRect layerFrame = destinationLayer.frame;
CGRect scaledRect = CGRectMake(layerFrame.origin.x,
layerFrame.origin.y,
(layerFrame.size.width)*scaledFactor,
(layerFrame.size.height)*scaledFactor);
// Get the size and do some drawings
CGSize sizeBack = CGSizeMake(layerFrame.size.width*scaledFactor, layerFrame.size.height*scaledFactor);
UIGraphicsBeginImageContext(sizeBack);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBFillColor(context, 0., 0., 0., 1.);
drawBorder(context, scaledRect);
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
if (destinationLayer) {
[destinationLayer setContents:(id)img.CGImage];
}
}
The most important lines are
UIGraphicsBeginImageContext(sizeBack);
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();