iOS应用开发中对UIImage进行截取和缩放的方法详解

易采站长站为您分析iOS应用开发中对UIImage进行截取和缩放的方法,分别讲解了如何截取指定区域大小的UIImage以及缩放到指定大小和等比缩放的具体操作过程,需要的朋友可以参考下  

截取UIImage指定大小区域
最近遇到这样的需求：从服务器获取到一张照片，只需要显示他的左半部分，或者中间部分等等。也就是截取UIImage指定大小区域。

UIImage扩展：

我的解决方案是对UIImage进行扩展。通过CGImageRef和CGImage完成截取，调用的方法是：CGImageCreateWithImageInRect。扩展类叫UIImage+Crop，具体代码如下：

UIImage+Crop.h

#import <UIKit/UIKit.h>

typedef NS_ENUM(NSInteger, XYCropImageStyle){
  XYCropImageStyleRight        =0,   // 右半部分
  XYCropImageStyleCenter       =1,   // 中间部分
  XYCropImageStyleLeft        =2,   // 左半部分
  XYCropImageStyleRightOneOfThird   =3,   // 右侧三分之一部分
  XYCropImageStyleCenterOneOfThird  =4,   // 中间三分之一部分
  XYCropImageStyleLeftOneOfThird   =5,   // 左侧三分之一部分
  XYCropImageStyleRightQuarter    =6,   // 右侧四分之一部分
  XYCropImageStyleCenterRightQuarter =7,   // 中间右侧四分之一部分
  XYCropImageStyleCenterLeftQuarter  =8,   // 中间左侧四分之一部分
  XYCropImageStyleLeftQuarter     =9,   // 左侧四分之一部分
};

@interface UIImage (Crop)
- (UIImage *)imageByCroppingWithStyle:(XYCropImageStyle)style;

@end
UIImage+Crop.m

#import "UIImage+Crop.h"

@implementation UIImage (Crop)

- (UIImage *)imageByCroppingWithStyle:(XYCropImageStyle)style
{
  CGRect rect;
  switch (style) {
    case XYCropImageStyleLeft:
      rect = CGRectMake(0, 0, self.size.width/2, self.size.height);
      break;
    case XYCropImageStyleCenter:
      rect = CGRectMake(self.size.width/4, 0, self.size.width/2, self.size.height);
      break;
    case XYCropImageStyleRight:
      rect = CGRectMake(self.size.width/2, 0, self.size.width/2, self.size.height);
      break;
    case XYCropImageStyleLeftOneOfThird:
      rect = CGRectMake(0, 0, self.size.width/3, self.size.height);
      break;
    case XYCropImageStyleCenterOneOfThird:
      rect = CGRectMake(self.size.width/3, 0, self.size.width/3, self.size.height);
      break;
    case XYCropImageStyleRightOneOfThird:
      rect = CGRectMake(self.size.width/3*2, 0, self.size.width/3, self.size.height);
      break;
    case XYCropImageStyleLeftQuarter:
      rect = CGRectMake(0, 0, self.size.width/4, self.size.height);
      break;
    case XYCropImageStyleCenterLeftQuarter:
      rect = CGRectMake(self.size.width/4, 0, self.size.width/4, self.size.height);
      break;
    case XYCropImageStyleCenterRightQuarter:
      rect = CGRectMake(self.size.width/4*2, 0, self.size.width/4, self.size.height);
      break;
    case XYCropImageStyleRightQuarter:
      rect = CGRectMake(self.size.width/4*3, 0, self.size.width/4, self.size.height);
      break;
    default:
      break;
  }
  CGImageRef imageRef = self.CGImage;
  CGImageRef imagePartRef = CGImageCreateWithImageInRect(imageRef, rect);
  UIImage *cropImage = [UIImage imageWithCGImage:imagePartRef];
  CGImageRelease(imagePartRef);
  return cropImage;
}

								 
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