提取UIImageView的一部分

Question

我想知道是否有可能"提取"一部分UIImageView.

例如,我选择使用Warp Affine作为其中一部分,UIImageView我知道所选部分frame.

像在这张图片中:

是否有可能从原来UIImageView只有选定的部分获得而不会失去质量？

Answer 1

通过类别方法获取视图的快照:

@implementation UIView(Snapshot)

-(UIImage*)makeSnapshot
{
  CGRect wholeRect = self.bounds;

  UIGraphicsBeginImageContextWithOptions(wholeRect.size, YES, [UIScreen mainScreen].scale);

  CGContextRef ctx = UIGraphicsGetCurrentContext();
  [[UIColor blackColor] set];
  CGContextFillRect(ctx, wholeRect);
  [self.layer renderInContext:ctx];

  UIImage* image = UIGraphicsGetImageFromCurrentImageContext();

  UIGraphicsEndImageContext();

  return image;
}

@end

然后通过另一种类别方法将其裁剪到您的rect:

@implementation UIImage(Crop)

-(UIImage*)cropFromRect:(CGRect)fromRect
{
  fromRect = CGRectMake(fromRect.origin.x * self.scale,
                        fromRect.origin.y * self.scale,
                        fromRect.size.width * self.scale,
                        fromRect.size.height * self.scale);
  CGImageRef imageRef = CGImageCreateWithImageInRect(self.CGImage, fromRect);
  UIImage* crop = [UIImage imageWithCGImage:imageRef scale:self.scale orientation:self.imageOrientation];
  CGImageRelease(imageRef);
  return crop;
}

@end

在你的VC中:

UIImage* snapshot = [self.imageView makeSnapshot];
UIImage* imageYouNeed = [snapshot cropFromRect:selectedRect];

selectedRect应该在你的self.imageView坐标系中,如果不是那么就用 selectedRect = [self.imageView convertRect:selectedRect fromView:...]