mask_bar calls QccWAVShapeAdaptiveMaskBAR(3) to measure the "complexity" of the shape of a transparency mask with a boundary-to-area ratio (BAR) defined as the total number of mask pixels that lie on the boundary of the opaque object expressed as a proportion of the total number of opaque pixels in the object. mask is the filename for the transparency mask.
J. E. Fowler, "Shape-Adaptive Tarp Coding," submitted to the 2003 International Conference on Image Processing, Barcelona, Spain, December 2002.
S. Li and W. Li, "Shape-Adaptive Discrete Wavelet Transforms for Arbitrarily Shaped Visual Object Coding," IEEE Transactions on Circuits and Systems for Video Coding, vol. 10, pp. 725-743, August 2000.