renderInContext: 截屏

官方给的该方法的说明

/** Rendering properties and methods. **/

/* Renders the receiver and its sublayers into 'ctx'. This method

* renders directly from the layer tree. Renders in the coordinate space

* of the layer.

* WARNING: currently this method does not implement the full

* CoreAnimation composition model, use with caution. */

- (void)renderInContext:(CGContextRef)ctx;

渲染一个图层和其子图层到 'ctx' ; 注意上面的WARNING:   not implement the full CoreAnimation composition model

//renderInContext:使用此函数实现截图，在有核心动画效果的视图上有差错: not implement the full CoreAnimation composition model

- (UIImage*)screenShotFromView:(UIView*)mainView

{

CGFloatscale = [UIScreenmainScreen].scale;

CGSizeshotSize =CGSizeMake(mainView.bounds.size.width*scale, mainView.bounds.size.height*scale);

UIGraphicsBeginImageContextWithOptions(shotSize,YES,0);

//设置截屏大小

[mainView.layerrenderInContext:UIGraphicsGetCurrentContext()];

UIImage*viewImage =UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

CGImageRefimageRef = viewImage.CGImage;

CGRectrect =CGRectMake(0,0, shotSize.width, shotSize.height);//这里可以设置想要截图的区域

CGImageRefimageRefRect =CGImageCreateWithImageInRect(imageRef, rect);

UIImage*image = [[UIImagealloc]initWithCGImage:imageRefRect];

//UIGraphicsBeginImageContext(mainView.bounds.size);

//[mainView.layer renderInContext:UIGraphicsGetCurrentContext()];

//UIImage *image= UIGraphicsGetImageFromCurrentImageContext();

//

//UIGraphicsEndImageContext();

//显示截图

//UIImageView *imaView = [[UIImageView alloc] initWithImage:image];

//imaView.frame = CGRectMake(0, 0, mainView.frame.size.width/2, mainView.frame.size.height/2);

//[[UIApplication sharedApplication].keyWindow addSubview:imaView];

//写入相册

//UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);

returnimage;

}