文章转载于知乎 砥砺

//将图片剪裁成圆形

 class func imagewithImage(image:UIImage) -> UIImage{ 
            let width = image.size.width
            let height = image.size.height
            let redius = ((width <= height) ? width : height)/2;
            let rect = CGRect(x: width/2-redius,y: height/2-redius,width: redius*2,height: redius*2); 
            let sourceImageRef = image.cgImage
            let newImageRef =  sourceImageRef?.cropping(to: rect)
            let newImage = UIImage(cgImage: newImageRef!)
                 UIGraphicsBeginImageContextWithOptions(CGSize(width:newImage.size.width,height: newImage.size.height), false, 0);
            let path = UIBezierPath(arcCenter: CGPoint(x: newImage.size.width / 2, y: newImage.size.height / 2), radius: redius, startAngle: 0, endAngle:CGFloat(Double.pi * 2.0), clockwise: false)
                path.addClip()
            newImage.draw(at: CGPoint.zero)
            let imageCut = UIGraphicsGetImageFromCurrentImageContext()
         return imageCut!
 }

//重设图片大小

 func reSizeImage(reSize:CGSize)->UIImage {
     //UIGraphicsBeginImageContext(reSize)
       UIGraphicsBeginImageContextWithOptions(reSize,false,UIScreen.main.scale)
       self.draw(in: CGRect(x: 0,y: 0,width: reSize.width,height: reSize.height))
       let reSizeImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()!
           UIGraphicsEndImageContext()
    return reSizeImage
 }

//OC版
(UIImage *) scaleImage:(UIImage *)image toScale:(float)scaleSize {
UIGraphicsBeginImageContext(CGSizeMake(image.size.width * scaleSize, image.size.height * scaleSize);
[image drawInRect:CGRectMake(0, 0, image.size.width * scaleSize, image.size.height * scaleSize)];
UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return scaledImage;
}

//等比率缩放

 func scaleImage(scaleSize:CGFloat)->UIImage {
        let reSize = CGSize(width:self.size.width * scaleSize,height: self.size.height * scaleSize)
     return reSizeImage(reSize: reSize)
 }

/**

* 压缩上传图片到指定字节

* image 压缩的图片

* maxLength 压缩后最大字节大小

* return 压缩后图片的二进制

*/


 func compressImage(image: UIImage, maxLength: Int) -> NSData? {
          let newSize = self.scaleImage(image: image, imageLength: 300)
          let newImage = self.resizeImage(image: image, newSize: newSize)
          var compress:CGFloat = 0.9
          var data = UIImageJPEGRepresentation(newImage, compress)
                    while (data?.count)! > maxLength && compress > 0.01 {
                          ompress -= 0.02
                          data = UIImageJPEGRepresentation(newImage, compress)
              } 
          return data! as NSData
 } 

/**

* 通过指定图片最长边，获得等比例的图片size

* image 原始图片

* imageLength 图片允许的最长宽度（高度）

* return 获得等比例的size

*/

 func scaleImage(image: UIImage, imageLength: CGFloat) -> CGSize {
            var newWidth:CGFloat = 0.0
            var newHeight:CGFloat = 0.0
            let width = image.size.width
            let height = image.size.height
          if (width > imageLength || height > imageLength){
                     if (width > height) {
                             newWidth = imageLength;
                             newHeight = newWidth * height / width;
                     }else if(height > width){
                             newHeight = imageLength;
                             newWidth = newHeight * width / height;
            }else{
                 newWidth = imageLength;
                   newHeight = imageLength;
                   } 
            }
      return CGSize(width: newWidth, height: newHeight)
 }

/**

* 获得指定size的图片

* image 原始图片

* newSize 指定的size

* return 调整后的图片

*/

 func resizeImage(image: UIImage, newSize: CGSize) -> UIImage {
             UIGraphicsBeginImageContext(newSize)
             image.draw(in: CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height))
         let newImage = UIGraphicsGetImageFromCurrentImageContext()
             UIGraphicsEndImageContext()
     return newImage!
 }