• blend(M, N)—Returns a blend of same-size matrices M and N (pixelwise sum - [product/255]).
The blend function combines two images. Blending is useful in subtracting and rebiasing backgrounds, which improves feature visibility.
• mask(M, N)—Returns matrix M masked by same-size matrix N - set to zero where N is zero, otherwise remains the same.
The mask function masks one image with the other. Masking can be used to black out part of an image so that processing can be done on the remaining features.