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Diagonally crop an image in Swift
/*
* Copyright (c) 2017 Ziga Dolar
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
import UIKit
extension UIImage {
public func diagonalCrop(_ points: (a: CGPoint, b: CGPoint), height: CGFloat) -> UIImage {
let cPoints = computeRectPoints(points, height: height)
let bounds = boundingRect(cPoints)
let bboxCropImage = cropImage(self, toRect: bounds)
let vec = CGPoint(x: points.b.x - points.a.x, y: points.b.y - points.a.y)
let width = sqrt(vec.x*vec.x + vec.y*vec.y)
let angle = atan2(vec.y, vec.x)
let rotatedImage = rotate(bboxCropImage, angle: angle)
let cropRect = CGRect(origin: CGPoint(x: (rotatedImage.size.width - width)/2,
y: (rotatedImage.size.height - height)/2),
size: CGSize(width: width, height: height))
return cropImage(rotatedImage, toRect: cropRect)
}
func cropImage(_ image: UIImage, toRect: CGRect) -> UIImage {
let cgImage: CGImage = (image.cgImage?.cropping(to: toRect))!
return UIImage(cgImage: cgImage)
}
func computeRectPoints(_ points: (a: CGPoint, b: CGPoint), height: CGFloat) -> (a: CGPoint, b: CGPoint, c: CGPoint, d:CGPoint) {
let c = computePoint(points, height: height, clockwise: true)
let d = computePoint(points, height: height, clockwise: false)
return (a: points.a, b: points.b, c: c, d: d)
}
func computePoint(_ points: (a: CGPoint, b: CGPoint), height: CGFloat, clockwise: Bool) -> CGPoint {
let x = clockwise ? points.b : points.a
let y = clockwise ? points.a : points.b
let mult: CGFloat = clockwise ? 1 : -1
let len = sqrt(pow((x.x - y.x),2) + pow((x.y - y.y),2))
let cx = x.x + ((height * (y.y - x.y))/len * mult)
let cy = x.y + ((height * (x.x - y.x))/len * mult)
return CGPoint(x: cx, y: cy)
}
func boundingRect(_ points: (a: CGPoint, b: CGPoint, c: CGPoint, d:CGPoint)) -> CGRect {
let minX = min(min(points.a.x, points.b.x), min(points.c.x, points.d.x))
let minY = min(min(points.a.y, points.b.y), min(points.c.y, points.d.y))
let maxX = max(max(points.a.x, points.b.x), max(points.c.x, points.d.x))
let maxY = max(max(points.a.y, points.b.y), max(points.c.y, points.d.y))
return CGRect(x: minX, y: minY, width: maxX-minX, height: maxY-minY)
}
func rotate(_ image: UIImage, angle: CGFloat) -> UIImage {
if let imgRef = image.cgImage {
let width = imgRef.width
let height = imgRef.height
let imgRect = CGRect(x: 0, y: 0, width: width, height: height)
let transform = CGAffineTransform(rotationAngle:angle)
let rotatedRect = imgRect.applying(transform)
if let colorSpace = imgRef.colorSpace {
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue).union(CGBitmapInfo.byteOrder32Big)
if let bmContext = CGContext.init(data: nil,
width: Int(rotatedRect.size.width),
height: Int(rotatedRect.size.height),
bitsPerComponent: 8,
bytesPerRow: 0,
space: colorSpace,
bitmapInfo: bitmapInfo.rawValue) {
bmContext.setAllowsAntialiasing(true)
bmContext.interpolationQuality = .default
bmContext.translateBy(x: rotatedRect.size.width/2, y: rotatedRect.size.height/2)
bmContext.rotate(by: angle)
bmContext.translateBy(x: -rotatedRect.size.width/2, y: -rotatedRect.size.height/2)
bmContext.draw(imgRef, in: CGRect(origin: CGPoint(x: (rotatedRect.size.width - CGFloat(width))/2,
y: (rotatedRect.size.height - CGFloat(height))/2),
size: CGSize(width: width, height: height)))
if let cgImage = bmContext.makeImage() {
return UIImage.init(cgImage: cgImage)
}
return image
}
return image
}
return image
}
return image
}
}
@zigadolar

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@zigadolar zigadolar commented Jul 10, 2017

A UIImage extension, allowing for diagonally cropping a UIImage by providing two coordinates and the desired height of the resulting rectangle. The height is calculated perpendicularly to the angle of the points, pointing in the clockwise direction.

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