How to merge two UIImages while keeping the aspect ratio and size? - ios

Question

The code is added to Github to let you understand the real problem.
This is the hierarchy:
-- ViewController.View P [width: 375, height: 667]
---- UIImageView A [width: 375, height: 667] Name: imgBackground
[A is holding an image of size(1287,1662)]
---- UIImageView B [width: 100, height: 100] Name: imgForeground
[B is holding an image of size(2400,982)]
I am trying to merge A with B but the result is stretched.
This is the merge code:
func mixImagesWith(frontImage:UIImage?, backgroundImage: UIImage?, atPoint point:CGPoint, ofSize signatureSize:CGSize) -> UIImage {
let size = self.imgBackground.frame.size
UIGraphicsBeginImageContextWithOptions(size, false, UIScreen.main.scale)
backgroundImage?.draw(in: CGRect.init(x: 0, y: 0, width: size.width, height: size.height))
frontImage?.draw(in: CGRect.init(x: point.x, y: point.y, width: signatureSize.width, height: signatureSize.height))
let newImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
return newImage
}
Note:
.contentMode = .scaleAspectFit
Code works but the result is stretched.
See this line in code, let size = self.imgBackground.frame.size – I need to change this to fix the problem. Find the origin of subview with respect to UIImage size
Here's the screenshot to understand the problem:
What should I do to get the proper output of merge function?

Answer 1

You have two bugs in your code:
You should also calculate aspect for document image to fit it into UIImageView. In mergeImages() replace:
img.draw(in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
with:
img.draw(in: getAspectFitFrame(sizeImgView: size, sizeImage: img.size))
When calculating aspect you center image horizontally/vertically if its width/height less then UIImageView width/height. But instead of comparing newWidth and newHeight you should compare factors:
if hfactor > vfactor {
y = (sizeImgView.height - newHeight) / 2
} else {
x = (sizeImgView.width - newWidth) / 2
}

Answer 2

Try bellow code it works for me, hope it works for you too,
func addWaterMarkToImage(img:UIImage, sizeWaterMark:CGRect, waterMarkImage:UIImage, completion : ((UIImage)->())?){
handler = completion
let img2:UIImage = waterMarkImage
let rect = CGRect(x: 0, y: 0, width: img.size.width, height: img.size.height)
UIGraphicsBeginImageContext(img.size)
img.draw(in: rect)
let frameAspect:CGRect = getAspectFitFrame(sizeImgView: sizeWaterMark.size, sizeImage: waterMarkImage.size)
let frameOrig:CGRect = CGRect(x: sizeWaterMark.origin.x+frameAspect.origin.x, y: sizeWaterMark.origin.y+frameAspect.origin.y, width: frameAspect.size.width, height: frameAspect.size.height)
img2.draw(in: frameOrig, blendMode: .normal, alpha: 1)
let result = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
if handler != nil {
handler!(result!)
}
}
//MARK - Get Aspect Fit frame of UIImage
func getAspectFitFrame(sizeImgView:CGSize, sizeImage:CGSize) -> CGRect{
let imageSize:CGSize = sizeImage
let viewSize:CGSize = sizeImgView
let hfactor : CGFloat = imageSize.width/viewSize.width
let vfactor : CGFloat = imageSize.height/viewSize.height
let factor : CGFloat = max(hfactor, vfactor)
// Divide the size by the greater of the vertical or horizontal shrinkage factor
let newWidth : CGFloat = imageSize.width / factor
let newHeight : CGFloat = imageSize.height / factor
var x:CGFloat = 0.0
var y:CGFloat = 0.0
if newWidth > newHeight{
y = (sizeImgView.height - newHeight)/2
}
if newHeight > newWidth{
x = (sizeImgView.width - newWidth)/2
}
let newRect:CGRect = CGRect(x: x, y: y, width: newWidth, height: newHeight)
return newRect
}