Why resize the cropped face before measurement

[zheng1237]

Hello, I don't get why do you resize the cropped face from its original shape to a fixed (190, 250) and then do the measurement on the resized landmarks. Shouldn't we measure on the original face landmarks?

[zementalist]

Hi,

Why reshape to a fixed shape?

• The original cropped-face-image dimensions differ from one to another, so it wouldn't be fair to measure on different scales, for example, a selfie image of shape 1024x768 will result in large measures compared to -even- the same person with different image of shape 416x228.

Why is it (190, 250)?

• This ratio is inferred from the average ratio of human face-width to face-length for a few thousands un-reshaped cropped-face-images, the important factor here is the ratio 190:250 or (width = 0.76 x length), you can change the shape but keep the ratio and use the same shape for all your measures to be on the same scale & distribution

[zheng1237]

Thanks for your quick reply.

Still, I feel it's a little confused why reshape to a fixed shape.

Yes, it's unfair to measure on different scales, but if we reshape to 190:250 or any other ratio or even normalize the landmarks, the original face will be scaled. The measured features on the scaled face won't represent the measured features of the original face.

I think given only one image without any reference, what we can do is to measure scale invariant features, like the ratio between eye height and eye width, etc, not the scale variant features like the height, length, width per se.