截屏,裁剪图片，缩放图片

// 截屏
//    UIGraphicsBeginImageContext(self.view.frame.size);
//    [self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
//    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
//    UIGraphicsEndImageContext();
//    UIImageWriteToSavedPhotosAlbum(viewImage, nil, nil, nil);


// 裁剪图片
-(UIImage *) cutFromImage:(UIImage *)image inRect:(CGRect)rect{
    CGImageRef sourceImageRef = [image CGImage];
    CGImageRef newImageRef = CGImageCreateWithImageInRect(sourceImageRef, rect);
    UIImage *newImage = [UIImage imageWithCGImage:newImageRef];
    return newImage;
}
// 缩放图片
- (UIImage *) scaleFromImage: (UIImage *) image toSize: (CGSize) size
{
    UIGraphicsBeginImageContext(size);
    [image drawInRect:CGRectMake(0, 0, size.width, size.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}