iOS 自定义裁剪相册照片

一、自定义裁剪相册照片核心点

1、读取照片
2、自定义UI和初始化缩放比例
3、自由点缩放
4、裁剪指定区域

设计要求

1、保留边距，初始化居中铺满高亮区域
2、自由点缩放，铺满全屏
3、裁剪方形图片

image.png

二、视图层级搭建

1、最底层是UIScrollview，UIScrollview上放置UIimageView。
2、和UIScrollview同父视图，创建自定义navbarView。
3、和UIScrollview同父视图，创建一个mask模糊层，禁用手势，模糊层可以使用layer图层实现，或用4块小视图拼接都行。


- (void)createSubviews
{
    //注意： 此处不要使用约束布局，因为scrollview存在缩、滚动、弹簧动画等混合效果，使用约束计算容易崩溃
    self.scrollView.frame = CGRectMake(0, 0, DD_SCREEN_WIDTH, DD_SCREEN_HEIGHT);
    [self.view addSubview:self.scrollView];
    [self.scrollView addSubview:self.imageView];
    self.scrollView.contentInset =
    UIEdgeInsetsMake(self.contentInsetTop, self.contentInsetLeft, self.contentInsetTop, self.contentInsetLeft);
   
    [self.view addSubview:self.navBarView];
    [self.navBarView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.right.top.equalTo(self.view);
        make.height.mas_equalTo(navBarHeight);
    }];
   //镂空蒙层
    [self.view addSubview:self.maskView];
    [self.maskView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.right.bottom.equalTo(self.view);
        make.top.equalTo(self.view).offset(navBarHeight);
    }];
}

三、功能实现

1、读取照片

推荐使用iOS7新框架photokit。
注意：读取相册照片时，系统会两次回调resultHandler，第一次传出缩略图（模糊图），第二次会传出高清图（图片数据不完整时，存在回传失败，image为nil），要做校验处理。

- (void)setAssetPh:(PHAsset *)assetPh
{
    _assetPh = assetPh;
    self.image = nil;
    self.viewIndicator.hidden = NO;
    [self.viewIndicator startAnimating];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        PHImageRequestOptions *option = [PHImageRequestOptions new];
        option.synchronous = NO;
        [[DDWPhotoImageManger sharedInstance]  requestImageForAsset:assetPh targetSize:[DDWimagePickerManger sharedInstance].getImageSizeOfBrower contentMode:PHImageContentModeAspectFit options:option resultHandler:^(UIImage * _Nullable result, NSDictionary * _Nullable info) {
        //图片有可能读取失败，要做校验
            if (result) {
                self.image = result;
            }
            [self.viewIndicator stopAnimating];
            self.viewIndicator.hidden = YES;
        }];
    });
}

2、初始化UI 照片居中，铺满显示

- (void)setImage:(UIImage *)image
{
    if (image != _image) {
        _image = image;
        dispatch_async(dispatch_get_main_queue(), ^{
            self.imageView.image = image;
            CGSize maxSize = self.hollowSize;
            CGFloat widthRatio = maxSize.width / image.size.width;
            CGFloat heightRatio = maxSize.height / image.size.height;
            CGFloat initialZoom = (widthRatio > heightRatio) ? heightRatio : widthRatio;
            if (initialZoom > 1) {
                initialZoom = 1;
            }
            // 初始化显示imageView
            CGRect  initialFrame = self.scrollView.frame;
            initialFrame.size.width = image.size.width * initialZoom;
            initialFrame.size.height = image.size.height * initialZoom;
            self.imageView.frame = initialFrame;
            
            [self.scrollView setMinimumZoomScale:initialZoom];
            [self.scrollView setMaximumZoomScale:5];
            //初次铺满缩放
            self.isFirstZoom = YES;
            [self.scrollView setZoomScale:1.0];
            [self scrollViewDidZoom:self.scrollView];
        });
    }
}

3、自由点缩放

实现UIScrollViewDelegate的缩放方法，

#pragma mark- <UIScrollViewDelegate> Methods
- (void)scrollViewDidZoom:(UIScrollView *)scrollView
{
    CGFloat w_content = self.scrollView.contentSize.width;
    CGFloat h_content = self.scrollView.contentSize.height;

    //容错处理
    if (w_content <= 0) {
        w_content = self.hollowSize.width * 0.5;
    }
    if (h_content <= 0) {
        h_content = self.hollowSize.height * 0.5;
    }
    
    //限定铺满处理
    if (w_content < self.hollowSize.width) {
        h_content = h_content * self.hollowSize.width / w_content;
        w_content = self.hollowSize.width;
    }
    if (h_content < self.hollowSize.height) {
        w_content = w_content * self.hollowSize.height / h_content;
        h_content = self.hollowSize.height;
    }
    self.imageView.width = w_content;
    self.imageView.height = h_content;
    self.scrollView.contentSize = CGSizeMake(w_content, h_content);
    self.imageView.center = CGPointMake(self.scrollView.contentSize.width * 0.5 ,
                                        self.scrollView.contentSize.height * 0.5);
    if (self.isFirstZoom) {
       // 初始化缩放居中显示
        CGFloat offset_x = (self.imageView.frame.size.width - self.hollowSize.width) * 0.5 - self.contentInsetLeft;
        CGFloat offset_y = (self.imageView.frame.size.height - self.hollowSize.height) * 0.5 - self.contentInsetTop;
        [self.scrollView setContentOffset:CGPointMake(offset_x , offset_y) animated:NO];
        self.isFirstZoom = NO;
    }
}

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return self.imageView;
}

4、裁剪指定区域为图片

调用系统裁剪方法即可。

#pragma mark- 裁剪 Methods
- (UIImage *)getSubImage
{
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(self.hollowSize.width, self.hollowSize.height), YES, [UIScreen mainScreen].scale);
    CGPoint offset = self.scrollView.contentOffset;
    CGContextTranslateCTM(UIGraphicsGetCurrentContext(), -(offset.x + self.contentInsetLeft), -(offset.y + self.contentInsetTop));
    [self.scrollView.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    img = [self imageWithImage:img scaledToSize:CGSizeMake(self.hollowSize.width, self.hollowSize.height)];
    return img;
}

-(UIImage *)imageWithImage:(UIImage*)image scaledToSize:(CGSize)newSize
{
    UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
    [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}