iOS选择图片自定义系统裁剪框

使用场景举例,玩过微博发表长文章的应该都知道,可以选择封面图,这个封面图是有一定比例的,例如375/280,那我们怎么控制我们选择出来的图片一定是这比例呢,那就是截取这一比例的部分图片,有兴趣的朋友可以去微博看一下效果,下面我们来说一下实现方案.

需要调用的相册的控制器内代码

/**注意!控制器需实现相应代理*/
-(void)chooseImg {
    UIImagePickerController *pc = [[UIImagePickerController alloc]init];
    pc.delegate = self;
    [pc setSourceType:UIImagePickerControllerSourceTypePhotoLibrary];
    [pc setModalPresentationStyle:UIModalPresentationFullScreen];
    [pc setModalTransitionStyle:UIModalTransitionStyleCoverVertical];
    [pc setAllowsEditing:YES];
    [self presentViewController:pc animated:YES completion:nil];
}

//实现此方法,给系统相册增加方法
- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    if (navigationController.viewControllers.count == 3)
    {
        Method method = class_getInstanceMethod([self class], @selector(drawRect:));
        class_replaceMethod([[[[navigationController viewControllers][2].view subviews][1] subviews][0] class],@selector(drawRect:),method_getImplementation(method),method_getTypeEncoding(method));
    }
}

//我们需要的截取框(比例根据实际需要设置,此处为 375:280)
-(void)drawRect:(CGRect)rect
{
    CGContextRef ref = UIGraphicsGetCurrentContext();
    CGContextAddRect(ref, rect);
    
    CGFloat h = (APP_WIDTH * 280) / 375;
    CGContextAddRect(ref, CGRectMake(0, (APP_HEIGHT - h) * 0.5 , APP_WIDTH, h));
    [[UIColor colorWithRed:0 green:0 blue:0 alpha:0.5]setFill];
    CGContextDrawPath(ref, kCGPathEOFill);
    
    CGContextAddRect(ref, CGRectMake(0, (APP_HEIGHT - h) * 0.5 , APP_WIDTH, h));
    [[UIColor whiteColor]setStroke];
    CGContextStrokePath(ref);
}

//当得到照片或者视频后，调用该方法
-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info{
    NSLog(@"Picker returned successfully.");
    NSLog(@"%@", info);

    if (_isHeadClick) {
        NSLog(@"----%s",__func__);
    
        [picker dismissViewControllerAnimated:YES completion:nil];
        UIImage *image = [info objectForKey:UIImagePickerControllerEditedImage];
        NSLog(@"==image==%@",NSStringFromCGSize(image.size));
        //生成最终图片
        UIImage *image2 = [UIImage imagewithImage:image];
    }
}

UIImage+cutImage

.h文件

#import <UIKit/UIKit.h>

@interface UIImage (cutImage)
//将图片截成方形图片
+ (UIImage *)imagewithImage:(UIImage *)image;

@end

.m文件

#import "UIImage+cutImage.h"

@implementation UIImage (cutImage)

+ (UIImage *)imagewithImage:(UIImage *)image
{    
    CGFloat width = image.size.width;
    //因为实际的截图还是系统的剪切框截出来的图片,所以这里处理成我们自己实际需要的比例
    CGFloat resultH = width * 280 / 375;
    
    CGFloat height = image.size.height;    
    CGRect  rect = CGRectMake(0, (height - resultH) * 0.5, width, resultH);
    
    CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], rect);
    UIImage *thumbScale = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    return thumbScale;
}
@end

ps:个人觉得还不够完美,如有更完美方案还请告知