提取部分 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，我使用 Warp Affine 选择 UIImageView 的一部分，并且我知道所选部分 frame.

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

喜欢这张图片:

是否可以从原始UIImageView中只获取选定的部分而不损失质量?

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

推荐答案

通过category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

然后通过另一种类别方法将其裁剪到您的矩形:

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

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，如果没有那么使用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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