掌握iOS视图截屏技巧：精准捕捉，优化视效

1.将整个view截图返回image：

这些 api 已被废弃，所以需要判断 iOS 版本 写两套代码：
Replace usage of UIGraphicsBeginImageContextWithOptions with UIGraphicsImageRenderer.
Replace usage of UIGraphicsGetImageFromCurrentImageContext with UIGraphicsImageRendererContext.currentImage.

Swift 版本：

/// 截图整个view/// - Returns: imagefuncmooSnapshot()->UIImage?{ifself.window ==nil{returnnil}let scale =UIScreen.main.scale
    var image:UIImage?=nil// 1. 创建绘图渲染格式if#available(iOS 10.0,*){let format =UIGraphicsImageRendererFormat()
        format.scale = scale
        format.opaque =false// 2. 创建绘图渲染器let renderer =UIGraphicsImageRenderer(size:self.bounds.size,
                                               format: format)// 3. 绘制图
        image = renderer.image { context inlet success =self.drawHierarchy(in:self.bounds, afterScreenUpdates:true)print("draw success: \(success)")}}else{UIGraphicsBeginImageContextWithOptions(self.bounds.size,false, scale);let success =self.drawHierarchy(in:self.bounds, afterScreenUpdates:true)print("draw success: \(success)")
        image =UIGraphicsGetImageFromCurrentImageContext();UIGraphicsEndImageContext();}return image
}

OC版本：

-(UIImage * _Nullable)mooSnapshot {if(CGRectGetWidth(self.bounds)<=0.0||CGRectGetHeight(self.bounds)<=0.0){return nil;}if(!self.window){return nil;}if(!self.superview){return nil;}
    CGFloat scale =[UIScreen mainScreen].scale;
    UIImage *image = nil;if(@available(iOS 10.0,*)){
        UIGraphicsImageRendererFormat *format =[[UIGraphicsImageRendererFormat alloc] init];
        format.scale = scale;
        format.opaque = NO;
        UIGraphicsImageRenderer *renderer =[[UIGraphicsImageRenderer alloc] initWithSize:self.bounds.size
                                                                                   format:format];
        image =[renderer imageWithActions:^(UIGraphicsImageRendererContext * _Nonnull rendererContext){
            BOOL success =[self drawViewHierarchyInRect:self.bounds afterScreenUpdates:YES];NSLog(@"%p, Snapshot success: %@",self,@(success));}];}else{UIGraphicsBeginImageContextWithOptions(self.bounds.size, NO, scale);
        BOOL success =[self drawViewHierarchyInRect:self.bounds afterScreenUpdates:YES];NSLog(@"%p,  Snapshot success: %@",self,@(success));
        image =UIGraphicsGetImageFromCurrentImageContext();UIGraphicsEndImageContext();}return image;}

2.截取view的部分区域，返回image：

Capture the frame area of the view.

Swift 版本：

importCoreGraphicsextensionUIView{/// 截取view的部分区域/// - Parameter frame: 需要截取的区域/// - Returns: imagefuncmooSnapshotForFrame(_ frame:CGRect)->UIImage?{guardlet image =self.mooSnapshot()else{returnnil}guardlet cgImage = image.cgImage else{returnnil}let scale =UIScreen.main.scale
        // 根据屏幕倍率将 frame 进行缩放let scaledRect =CGRectApplyAffineTransform(frame,CGAffineTransformMakeScale(scale, scale))// 根据 缩放frame 进行裁剪guardlet scaledCGImage = cgImage.cropping(to: scaledRect)else{returnnil}let returnImage =UIImage(cgImage: scaledCGImage)return returnImage
    }}

OC 版本：

-(UIImage * _Nullable)mooSnapshotForFrame:(CGRect)frame {if(CGRectGetWidth(frame)<=0.0||CGRectGetHeight(frame)<=0.0){return nil;}
    UIImage *image =[self mooSnapshot];if(!image){return nil;}
    CGFloat scale =[UIScreen mainScreen].scale;
    CGRect scaledRect =CGRectApplyAffineTransform(frame,CGAffineTransformMakeScale(scale, scale));
    CGImageRef cgImage =CGImageCreateWithImageInRect(image.CGImage, scaledRect);
    UIImage *returnImage =[UIImage imageWithCGImage:cgImage];CGImageRelease(cgImage);return returnImage;}

以下就是将一个view的上半部分截取成image后展示如下：

3.旧方法：

funcmooSnapshot()->UIImage?{guardCGRectGetWidth(self.bounds)>0.0&&CGRectGetHeight(self.bounds)>0.0else{returnnil}UIGraphicsBeginImageContextWithOptions(self.bounds.size,false,0.0)let success =self.drawHierarchy(in:self.bounds, afterScreenUpdates:true)print("draw success: \(success)")let image =UIGraphicsGetImageFromCurrentImageContext()UIGraphicsEndPDFContext()return image
}

Replace usage of UIGraphicsBeginImageContext with UIGraphicsImageRenderer.
Replace usage of UIGraphicsBeginImageContextWithOptions with UIGraphicsImageRenderer.
Replace usage of UIGraphicsGetImageFromCurrentImageContext with UIGraphicsImageRendererContext.currentImage.
UIGraphicsEndImageContext should only be used alongside UIGraphicsBeginImageContext[WithOptions].
这些旧的 api 已经被废弃了，用文章开头的 api 代替

4.Tips

Tips1：得在加载到父视图 layout 后触发
Tips2：width 或 height 有一个为空 drawHierarchy 就会 crash（就版iOS不会crash，新版会）

参考：