剪切照片 crop Image （swift PK objec

object-c 的方式：

方式1

    CGFloat scale = [UIScreen mainScreen].scale;
    CGRect rectFrame = CGRectMake(frameFromRect.origin.x * scale, frameFromRect.origin.y * scale, frameFromRect.size.width * scale, frameFromRect.size.height * scale);
    CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], rectFrame);
    UIImage * croppedImage = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);

    readingView.image = croppedImage;```

方式2

/**
*从图片中按指定的位置大小截取图片的一部分

• UIImage image 原始的图片

• CGRect rect 要截取的区域
  */
  +(UIImage *)imageFromImage:(UIImage *)image inRect:(CGRect)rect{

  //将UIImage转换成CGImageRef
  CGImageRef sourceImageRef = [image CGImage];

  //按照给定的矩形区域进行剪裁
  CGImageRef newImageRef = CGImageCreateWithImageInRect(sourceImageRef, rect);

  //将CGImageRef转换成UIImage
  UIImage *newImage = [UIImage imageWithCGImage:newImageRef];

  CGImageRelease(newImageRef);

  //返回剪裁后的图片
  return newImage;
  }

swift 的方式： （直接剪切不惯病，直接剪切没毛病）

let screenScale = UIScreen.main.scale
let index = newView!.superview!.subviews.index(of: newView!)!
let subImageFrame = CGRect.init(x: frames[index].origin.xscreenScale, y: frames[index].origin.yscreenScale, width: frames[index].size.widthscreenScale, height: frames[index].size.heightscreenScale)

///核心代码就一句
let subImage = UIImage.init(cgImage:self.backImage!.cgImage!.cropping(to: subImageFrame)!)

newView?.image = subImage```