提取UIImageView的一部分 [英] Extract a part of UIImageView

问题描述

我想知道是否可以提取 UIImageView 的一部分。

I was wondering if it's possible to "extract" a part of UIImageView.

例如，我选择使用Warp Affine作为 UIImageView 的一部分，我知道所选部分 frame 。

For example, I select using Warp Affine a part of the UIImageView and I know the selected part frame.

如下图所示：

是否可以从原始 UIImageView获取只有选定的部分没有丢失质量？

Is it possible to get from the original UIImageView only the selected part without losing quality?

推荐答案

通过类别方法获取视图的快照：

Get the snapshot of the view via category method:

@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

然后将其裁剪到你的矩形通过另一种类别方法：

then crop it to your rect via another category method:

@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

：

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

selectedRect 应该在你身边 self.imageView 坐标系，如果没有则使用
selectedRect = [self.imageView convertRect：selectedRect fromView：...]

selectedRect should be in you self.imageView coordinate system, if no so then use selectedRect = [self.imageView convertRect:selectedRect fromView:...]

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