-(UIImage *)getImageFromImage :(UIImage*)BIGimg{
CGRect myImageRect = CGRectMake(0, BIGimg.size.height/2 - BIGimg.size.width/2, BIGimg.size.width, BIGimg.size.width);//这个CGRectMake 决定截图位置
UIImage* bigImage= BIGimg;
CGImageRef imageRef = bigImage.CGImage;
CGImageRef subImageRef = CGImageCreateWithImageInRect(imageRef, myImageRect);
CGSize size;
size.width = 60.0; //这两个量需要设置 也就是新的图片的大小
size.height = 60.0;
// 截取用的方法
UIGraphicsBeginImageContext(size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextDrawImage(context, myImageRect, subImageRef);
UIImage* smallImage = [UIImage imageWithCGImage:subImageRef];
UIGraphicsEndImageContext();
return smallImage;
}