Center crop ImageProcessor

[newmanw]

Issue #320 talks about a crop image processor.

Do you think a center crop image processor fits into the current collection of core processors?

[onevcat]

Sure, it could be a great improvement! Do you have time to implement it? (or I will handle it later since I'm getting quite busy for now)

[newmanw]

I can certainly take a crack at it, with a warning that I just started using swift ;)

Do you think it makes more sense as a separate ImageProcessor, or possibly as part of options passed to the current resize processor?

[onevcat]

I believe it would be better to be a new one :)

[onevcat]

With crop anchor as parameter, and center as its default value.

[lpbas]

I put together a quick centre crop processor that I needed for my app, posting it here for anyone that might need it. I have not implemented the anchor yet, if I do I'll create a pull request. :) (P.S.: The code was found on stack overflow, I just put it in an ImageProcessor)

import Foundation
import Kingfisher

/// Processor for cropping the center of an image
public struct CenterCropImageProcessor: ImageProcessor {
		public let identifier: String
		
		/// Center point to crop to.
		public var centerPoint: CGFloat = 0.0
		
		/// Initialize a `CenterCropImageProcessor`
		///
		/// - parameter centerPoint: The center point to crop to.
		///
		/// - returns: An initialized `CenterCropImageProcessor`.
		public init(centerPoint: CGFloat? = nil) {
			if let center = centerPoint {
				self.centerPoint = center
			}
			self.identifier = "com.l4grange.CenterCropImageProcessor(\(centerPoint))"
		}
		
		public func process(item: ImageProcessItem, options: KingfisherOptionsInfo) -> Image? {
			switch item {
			case .image(let image):
				
				var imageHeight = image.size.height
				var imageWidth = image.size.width
							
				if imageHeight > imageWidth {
					imageHeight = imageWidth
				}
				else {
					imageWidth = imageHeight
				}
							
				let size = CGSize(width: imageWidth, height: imageHeight)
							
				let refWidth : CGFloat = CGFloat(image.cgImage!.width)
				let refHeight : CGFloat = CGFloat(image.cgImage!.height)
							
				let x = (refWidth - size.width) / 2
				let y = (refHeight - size.height) / 2
							
				let cropRect = CGRect(x: x, y: y, width: size.height, height: size.width)
				if let imageRef = image.cgImage!.cropping(to: cropRect) {
					return UIImage(cgImage: imageRef, scale: 0, orientation: image.imageOrientation)
				}
				
				return nil
				
			case .data(_):
				return (DefaultImageProcessor.default >> self).process(item: item, options: options)
			}
		}
}

[onevcat]

@L4grange Good job! I'll take a look at it to see whether we could implement a built-in crop processor based on this.

[onevcat]

Cropping image is implemented in #630 now.

[mhtranbn]

how i can crop image @onevcat many thank for support, great respo!

[onevcat]

Just create a CroppingImageProcessor and pass it as an option to setImage methods. Please have a look at our wiki for more.