Two boxes, same points? about dlib-models

[davisking]

Yes this is the reason. The two sets of boxes come from dlib's two face detectors. Training on both of them causes the resulting model to work well for both face detectors, since as you noted, the landmarking model's predictions are seeded from the position of the bounding box. So boxes that are placed systematically different from how they appear in training data would result in worse performance. Since the two face detectors use slightly different box annotation schemes this would be a problem if the landmarking model wasn't trained to be aware of this.

[davisking]

It’s just how I cropped them. The border is so far from the faces that it is not involved in the computation.

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On Jun 29, 2019, at 10:48 PM, Riley Tallman ***@***.***> wrote: Thank you for responding, it makes sense. Another question: why is there a black border on many of the pictures? And why are their dimensions square? I flipped through the first 50 and noticed many of them are 711x711 or 411x411 and a few other dimensions. How will the black pixels affect the training, and the resulting model? The training is done in the shape_predictor_trainer.h file, but I don't understand it well enough to answer my own question. — You are receiving this because you commented. Reply to this email directly, view it on GitHub, or mute the thread.

[realleyriley]

After thinking about it just now, I think the two boxes might be for making the landmark predictor more robust. I ran the script below to find any boxes that had different landmark coordinates, but I found nothing. By using different boxes, the shape predictor can train itself to identify landmarks more generally. The landmark predictor takes in the bounding box as input, and by training it on different bounding boxes, we can expand the training set I believe.

import xml.etree.ElementTree as ET
root = ET.parse('train_cleaned.xml').getroot()`

for image in root.find('images').findall('image'):
    boxes = image.findall('box')    # find all boxes in this image
    if(len(boxes) < 1):
        print('no boxes? ', image.attrib)
    if(len(boxes) > 1):             # some images only have one box
        parts0 = [part.attrib for part in boxes[0].findall('part')]
        parts1 = [part.attrib for part in boxes[1].findall('part')]
        if(parts0 != parts1):
            print('unequal points ', image.attrib)

[realleyriley]

Thank you for responding, it makes sense.

Another question: why is there a black border on many of the pictures? And why are their dimensions square? I flipped through the first 50 and noticed many of them are 711x711 or 411x411 and a few other dimensions.
How will the black pixels affect the training, and the resulting model?

The training is done in the shape_predictor_trainer.h file, but I don't understand it well enough to answer my own question.