ios - UIImage 人脸检测

Question

我正在尝试编写一个例程，它接受一个 UIImage 并返回一个仅包含面部的新 UIImage。这看起来非常简单，但我的大脑在处理 CoreImage 与 UIImage 空间时遇到了问题。

基础知识:

- (UIImage *)imageFromImage:(UIImage *)image inRect:(CGRect)rect {
    CGImageRef sourceImageRef = [image CGImage];
    CGImageRef newImageRef = CGImageCreateWithImageInRect(sourceImageRef, rect);
    UIImage *newImage = [UIImage imageWithCGImage:newImageRef];
    CGImageRelease(newImageRef);
    return newImage;
}


-(UIImage *)getFaceImage:(UIImage *)picture {
  CIDetector  *detector = [CIDetector detectorOfType:CIDetectorTypeFace 
                                             context:nil 
                                             options:[NSDictionary dictionaryWithObject: CIDetectorAccuracyHigh forKey: CIDetectorAccuracy]];

  CIImage *ciImage = [CIImage imageWithCGImage: [picture CGImage]];
  NSArray *features = [detector featuresInImage:ciImage];

  // For simplicity, I'm grabbing the first one in this code sample,
  // and we can all pretend that the photo has one face for sure. :-)
  CIFaceFeature *faceFeature = [features objectAtIndex:0];

  return imageFromImage:picture inRect:faceFeature.bounds;
}

返回的图像来自翻转后的图像。我试过使用这样的方式调整 faceFeature.bounds:

CGAffineTransform t = CGAffineTransformMakeScale(1.0f,-1.0f);
CGRect newRect = CGRectApplyAffineTransform(faceFeature.bounds,t);

...但这给了我图像之外的结果。

我敢肯定有一些简单的方法可以解决这个问题，但是如果没有计算自下而上然后使用它作为 X 创建一个新的矩形，是否有“正确”的方法来做到这一点？

谢谢!

Answer 1

仅使用 CIContext 从图像中裁剪脸部会更容易，也不会那么困惑。像这样:

CGImageRef cgImage = [_ciContext createCGImage:[CIImage imageWithCGImage:inputImage.CGImage] fromRect:faceFeature.bounds];
UIImage *croppedFace = [UIImage imageWithCGImage:cgImage];

inputImage 是您的 UIImage 对象，faceFeature 对象是您从[CIDetector featuresInImage:] 方法获得的 CIFaceFeature 类型。 p>