[英]How to get pixel color at location from UIimage scaled within a UIimageView
[英]How to extract the UIImage from rotated, scaled and inverted UIImageView in iOS
我正在从图库中拍摄图像,并使用CGAffineTransform应用缩放,旋转和反转转换。 最后,我将图像保存到图库。 但是,已保存的图像具有白色矩形边界![具有白色背景的旋转UIImageView] [1]。
- (UIImage *)getTheTransformedOriginalImage:(UIImage *)aTransImage
{
CGAffineTransform transform = selImageView.transform;
CGPathRef rotatedImageRectPath = CGPathCreateWithRect(selImageView.frame, &transform);
CGRect boundingBox = CGPathGetBoundingBox(rotatedImageRectPath);
CGSize rotatedSize = boundingBox.size;
UIGraphicsBeginImageContext(rotatedSize);
UIGraphicsBeginImageContextWithOptions(rotatedSize, NO, 0.0f);
// Move the origin to the middle of the image so we will rotate and scale around the center.
CGContextTranslateCTM(UIGraphicsGetCurrentContext(), rotatedSize.width/2, rotatedSize.height/2);
//Rotate the image context using tranform
CGContextConcatCTM(UIGraphicsGetCurrentContext(), selImageView.transform);
// Now, draw the rotated/scaled image into the context
CGContextScaleCTM(UIGraphicsGetCurrentContext(), 1.0, -1.0);
CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(-aTransImage.size.width / 2, -aTransImage.size.height / 2, aTransImage.size.width, aTransImage.size.height), [aTransImage CGImage]);
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
- (IBAction)saveToGalleryClicked:(id)sender
{
UIImage *aTransImage = selImageView.image;
UIImage *shareImage = [self getTheTransformedOriginalImage:aTransImage]
UIImageWriteToSavedPhotosAlbum(shareImage, nil, nil, nil);
}
我在附件中添加了旋转的UIImage。
为了没有白色背景(即不透明图像),您需要使用其他函数来开始图像上下文:
UIGraphicsBeginImageContextWithOptions(CGSize size, **BOOL opaque**, CGFloat scale)
因此,请替换:
UIGraphicsBeginImageContext(rotatedSize);
带有:
UIGraphicsBeginImageContextWithOptions(rotatedSize, NO, [[UIScreen mainScreen]scale])
这样可以确保上下文透明地绘制。
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