iOS---如何截图，如何将图片保存到相册

- (void)viewDidLoad {
[super viewDidLoad];
UIButton * btn = [UIButton buttonWithType:UIButtonTypeContactAdd];
btn.frame =CGRectMake(30, 30, 30, 30);
[self.view addSubview:btn];
[btn addTarget:self action:@selector(btnClick:) forControlEvents:UIControlEventTouchUpInside];
}
-(void)btnClick:(UIButton *)sender
{
[self savePhoto];
}
// 保存图片到相册功能，ALAssetsLibraryiOS9.0 以后用photoliabary 替代，
-(void)savePhoto
{
UIImage * image = [self captureImageFromView:self.view];
ALAssetsLibrary * library = [ALAssetsLibrary new];
NSData * data = UIImageJPEGRepresentation(image, 1.0);
[library writeImageDataToSavedPhotosAlbum:data metadata:nil completionBlock:nil];
}
//截图功能
-(UIImage *)captureImageFromView:(UIView *)view
{
CGRect screenRect = [view bounds];
UIGraphicsBeginImageContext(screenRect.size);
CGContextRef ctx = UIGraphicsGetCurrentContext();
[view.layer renderInContext:ctx];
UIImage * image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}