How to crop a UIImage without losing it's scale property? - ios

Question

Goal: Crop a UIImage (that starts with a scale property of 2.0)
I perform the following code:
let croppedCGImage = originalUIImage.cgImage!.cropping(to: cropRect)
let croppedUIImage = UIImage(cgImage: croppedCGImage!)
This code works, however the result, croppedUIImage, has an incorrect scale property of 1.0.
I've tried specifying the scale when creating the final image:
let croppedUIImage = UIImage(cgImage: croppedCGImage!, scale: 2.0, orientation: .up)
This yields the correct scale, but it cuts the size dimensions in half incorrectly.
What should I do here?
(*Note: the scale property on the UIImage is important because I later save the image with UIImagePNGRepresentation(_ image: UIImage) which is affected by the scale property)
Edit:
I got the following to work. Unfortunately it's just substantially slower than the CGImage cropping function.
extension UIImage {
func cropping(to rect: CGRect) -> UIImage {
UIGraphicsBeginImageContextWithOptions(rect.size, false, self.scale)
self.draw(in: CGRect(x: -rect.origin.x, y: -rect.origin.y, width: self.size.width, height: self.size.height))
let croppedImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
return croppedImage
}
}

Answer 1

Try this:
extension UIImage {
func imageByCropToRect(rect:CGRect, scale:Bool) -> UIImage {
var rect = rect
var scaleFactor: CGFloat = 1.0
if scale {
scaleFactor = self.scale
rect.origin.x *= scaleFactor
rect.origin.y *= scaleFactor
rect.size.width *= scaleFactor
rect.size.height *= scaleFactor
}
var image: UIImage? = nil;
if rect.size.width > 0 && rect.size.height > 0 {
let imageRef = self.cgImage!.cropping(to: rect)
image = UIImage(cgImage: imageRef!, scale: scaleFactor, orientation: self.imageOrientation)
}
return image!
}
}

Answer 2

Use this Extension :-
extension UIImage {
func cropping(to quality: CGInterpolationQuality, rect: CGRect) -> UIImage {
UIGraphicsBeginImageContextWithOptions(rect.size, false, self.scale)
let context = UIGraphicsGetCurrentContext()! as CGContext
context.interpolationQuality = quality
let drawRect : CGRect = CGRect(x: -rect.origin.x, y: -rect.origin.y, width: self.size.width, height: self.size.height)
context.clip(to: CGRect(x:0, y:0, width: rect.size.width, height: rect.size.height))
self.draw(in: drawRect)
let croppedImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
return croppedImage
}
}

Answer 3

I'm using the ImageHelper Pod for iOS and tvOS and it's working perfectly and might also fit your needs.
It brings a lot UIImage Extensions such as:
Crop and Resize
// Crops an image to a new rect
func crop(bounds: CGRect) -> UIImage?
// Crops an image to a centered square
func cropToSquare() -> UIImage? {
// Resizes an image
func resize(size:CGSize, contentMode: UIImageContentMode = .ScaleToFill) -> UIImage?
Screen Density
// To create an image that is Retina aware, use the screen scale as a multiplier for your size. You should also use this technique for padding or borders.
let width = 140 * UIScreen.mainScreen().scale
let height = 140 * UIScreen.mainScreen().scale
let image = UIImage(named: "myImage")?.resize(CGSize(width: width, height: height))
Also stuff like: Image Effects
// Applies a light blur effect to the image
func applyLightEffect() -> UIImage?
// Applies a extra light blur effect to the image
func applyExtraLightEffect() -> UIImage?
// Applies a dark blur effect to the image
func applyDarkEffect() -> UIImage?
// Applies a color tint to an image
func applyTintEffect(tintColor: UIColor) -> UIImage?
// Applies a blur to an image based on the specified radius, tint color saturation and mask image
func applyBlur(blurRadius:CGFloat, tintColor:UIColor?, saturationDeltaFactor:CGFloat, maskImage:UIImage? = nil) -> UIImage?

Answer 4

-(UIImage *)getNeedImageFrom:(UIImage*)image cropRect:(CGRect)rect
{
CGImageRef subImage = CGImageCreateWithImageInRect(image.CGImage, rect);
UIImage *croppedImage = [UIImage imageWithCGImage:subImage];
CGImageRelease(subImage);
return croppedImage;
}
calling
UIImage *imageSample=image;
CGRect rectMake1=CGRectMake(0, 0,imageSample.size.width*1/4, imageSample.size.height);
UIImage *img1=[[JRGlobal sharedInstance] getNeedImageFrom:imageSample cropRect:rectMake1];