如何在Swift中裁剪UIImage？ [英] How do I crop a UIImage in Swift?

问题描述

我想在Swift中编写一个函数，它可以拍摄一个图像并将除了中间的细水平之外的所有内容裁剪掉。我不想保留宽高比。

I want to write a function in Swift that takes an image and crops out everything except a thin horizontal like in the middle. I don't want to preserve the aspect ratio.

这是我到目前为止所做的，但它不能按照我想要的方式工作。我想只保留y = 276到y = 299的像素。

This is what I have so far but it doesn't work the way I want it to. I want to only preserve the pixels from y=276 to y=299.

func cropImageToBars(image: UIImage) -> UIImage {

  let rect = CGRectMake(0, 200, image.size.width, 23)

  UIGraphicsBeginImageContextWithOptions(rect.size, false, 1.0)
  image.drawInRect(rect)
  let newImage = UIGraphicsGetImageFromCurrentImageContext()
  UIGraphicsEndImageContext()

  return newImage

}

推荐答案

这个怎么样

func cropImageToBars(image: UIImage) -> UIImage {

    let rect = CGRectMake(0, 200, image.size.width, 23)

    UIGraphicsBeginImageContextWithOptions(rect.size, false, 0)
    defer{
      UIGraphicsEndImageContext()
    }
   flipContextVertically(rect.size)

   let cgImage = CGImageCreateWithImageInRect(image.CGImage, rect)!
   return UIImage(CGImage: cgImage) 
}

func flipContextVertically(contentSize:CGSize){
    var transform = CGAffineTransformIdentity
    transform = CGAffineTransformScale(transform, 1, -1)
    transform = CGAffineTransformTranslate(transform, 0, -contentSize.height)

    CGContextConcatCTM(UIGraphicsGetCurrentContext(), transform)
}

编辑翻转CG坐标以匹配UIKit。

EDIT Flipped the CG coordinate to match UIKit.

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