ERROR: Return 0 faces because error exists in btk_FaceFinder_putDCR.
Solution:
Creates a FaceDetector, configured with
the size of the images to be analysed and the maximum number of faces that can be detected. These parameters cannot be changed once the object is constructed.
Note that the width of the image must be even.
传入的图片的宽度必须是偶数的. 真蛋疼!