[英]When using avfoundation - crop visible portion of captured image represented in display layer
[英]AVFoundation crop captured still image according to the preview aspect ratio
我的问题与这个问题大体相似:
我有一个使用 AVFoundation 来捕获静止图像的应用程序。 我的 AVCaptureVideoPreviewLayer 具有 AVLayerVideoGravityResizeAspectFill 视频重力,因此可以从顶部和底部裁剪向用户显示的预览图片。
当用户按下“捕获”按钮时,实际捕获的图像与显示给用户的预览图片不同。 我的问题是如何相应地裁剪捕获的图像?
提前致谢。
我使用了此处提供的UIImage+Resize
类别和我编写的一些新方法来完成这项工作。 我重新格式化了一些代码以使其看起来更好并且未经测试,但它应该可以工作。 :))
- (UIImage*)cropAndResizeAspectFillWithSize:(CGSize)targetSize
interpolationQuality:(CGInterpolationQuality)quality {
UIImage *outputImage = nil;
UIImage *imageForProcessing = self;
// crop center square (AspectFill)
if (self.size.width != self.size.height) {
CGFloat shorterLength = 0;
CGPoint origin = CGPointZero;
if (self.size.width > self.size.height) {
origin.x = (self.size.width - self.size.height)/2;
shorterLength = self.size.height;
}
else {
origin.y = (self.size.height - self.size.width)/2;
shorterLength = self.size.width;
}
imageForProcessing = [imageForProcessing normalizedImage];
imageForProcessing = [imageForProcessing croppedImage:CGRectMake(origin.x, origin.y, shorterLength, shorterLength)];
}
outputImage = [imageForProcessing resizedImage:targetSize interpolationQuality:quality];
return outputImage;
}
// fix image orientation, which may wrongly rotate the output.
- (UIImage *)normalizedImage {
if (self.imageOrientation == UIImageOrientationUp) return self;
UIGraphicsBeginImageContextWithOptions(self.size, NO, self.scale);
[self drawInRect:(CGRect){0, 0, self.size}];
UIImage *normalizedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return normalizedImage;
}
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