adientMag/gradientHist.

 Additionally, custom channels can be specified via an optional struct
 array &quot;pCustom&quot; which may have 0 or more custom channel definitions. Each
 custom channel is generated via a call to &quot;chns=feval(hFunc,I,pFunc{:})&quot;.
 The color space of I is determined by pColor.colorSpace, use the setting
 colorSpace='orig' if the input image is not an 'rgb' image and should be
 left unchanged (e.g. if I has multiple channels). The input I will have
 type single and the outp