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;

}

实际运用

简单测试一下，看看有没有实现我们想要的效果。首先，先加载一个完整的UIImageView。这个应该不难。代码如下：

UIImageView *imgView = [[UIImageView alloc] init];

imgView.frame = CGRectMake((SCREEN.width - 226) / 2, 100, 226, 106);

UIImage *image = [UIImage imageNamed:@"ganggang"];

imgView.image = image;

[self.view addSubview:imgView];

运行一下：

要对UIImage进行裁剪，首先导入头文件：

#import "UIImage+Crop.h"

在上面UIImage *image = [UIImage imageNamed:@"ganggang"];这段代码之后加上下面这句：

image = [image imageByCroppingWithStyle:XYCropImageStyleLeft];

XYCropImageStyleLeft是截取照片的左半部分。效果如下：

截取成功，还可以截取其他区域的，只需要传入不同的XYCropImageStyle即可实现。以上代码依然在iOSStrongDemo里。