How to get simple face detection working? - firebase

Question

I am trying to get a simple example of face detection working with ML Kit on iOS. Here is excerpts of the Objective C code:
FIRVisionFaceDetectorOptions *faceDetectorOptions;
FIRVision *vision;
FIRVisionFaceDetector *faceDetector;
faceDetectorOptions = [[FIRVisionFaceDetectorOptions alloc] init];
faceDetectorOptions.performanceMode = FIRVisionFaceDetectorPerformanceModeAccurate;
faceDetectorOptions.landmarkMode = FIRVisionFaceDetectorLandmarkModeAll;
faceDetectorOptions.contourMode = FIRVisionFaceDetectorContourModeNone;
faceDetectorOptions.classificationMode = FIRVisionFaceDetectorClassificationModeAll;
faceDetectorOptions.minFaceSize = 0.1; // TODO: finalize this option value
vision = [FIRVision vision];
faceDetector = [vision faceDetectorWithOptions:faceDetectorOptions];
UIImage *staticImg = [UIImage imageNamed:#"sample.jpg"];
FIRVisionImage *visionImage = [[FIRVisionImage alloc] initWithImage:staticImg];
NSError* error = Nil;
NSArray<FIRVisionFace *> * faces = [faceDetector resultsInImage:visionImage error:&error];
NSLog(#"Synchronous result. error = %#, face count = %lu", error, faces.count);
The sample.jpg file is the following image downloaded and added as a resource to my Xcode project:
http://chwb.org/wp-content/uploads/2014/01/Theo_Janssen-Face1.jpg
The resultsInImage returns no error, but no faces either. It logs:
Synchronous result. error = (null), face count = 0
Am I doing something wrong?

Answer 1

I figured it out. The problem was I need to set the image metadata with orientation like this:
FIRVisionImageMetadata *imageMetadata = [FIRVisionImageMetadata new];
imageMetadata.orientation = [FcFaceDetector visionImageOrientationFromImageOrientation:uiImage.imageOrientation];
visionImage.metadata = imageMetadata;
+ (FIRVisionDetectorImageOrientation) visionImageOrientationFromImageOrientation:(UIImageOrientation)imageOrientation {
switch (imageOrientation) {
case UIImageOrientationUp:
return FIRVisionDetectorImageOrientationTopLeft;
case UIImageOrientationDown:
return FIRVisionDetectorImageOrientationBottomRight;
case UIImageOrientationLeft:
return FIRVisionDetectorImageOrientationLeftBottom;
case UIImageOrientationRight:
return FIRVisionDetectorImageOrientationRightTop;
case UIImageOrientationUpMirrored:
return FIRVisionDetectorImageOrientationTopRight;
case UIImageOrientationDownMirrored:
return FIRVisionDetectorImageOrientationBottomLeft;
case UIImageOrientationLeftMirrored:
return FIRVisionDetectorImageOrientationLeftTop;
case UIImageOrientationRightMirrored:
return FIRVisionDetectorImageOrientationRightBottom;
}
}
The docs seem to be unclear about it, because it seems to suggest to not set it:
https://firebase.google.com/docs/ml-kit/ios/detect-faces#2-run-the-face-detector