Calculates the gray histogram of an image. \n
* Image must be (IM_BYTE, IM_SHORT or IM_USHORT)/(IM_RGB, IM_GRAY, IM_BINARY or IM_MAP). \n
* If the image is IM_RGB then the histogram of the luma component is calculated. \n
* Histogram is always 256 or 65536 positions long. \n
* When cumulative is different from zero it calculates the cumulative histogram.
*
* \verbatim im.CalcGrayHistogram(image: imImage, cumulative: boolean) -> histo: table of numbers [in Lua 5] \endverbatim
* \ingroup stats
Calculates the gray histogram of an image. \n * Image must be (IM_BYTE, IM_SHORT or IM_USHORT)/(IM_RGB, IM_GRAY, IM_BINARY or IM_MAP). \n * If the image is IM_RGB then the histogram of the luma component is calculated. \n * Histogram is always 256 or 65536 positions long. \n * When cumulative is different from zero it calculates the cumulative histogram. * * \verbatim im.CalcGrayHistogram(image: imImage, cumulative: boolean) -> histo: table of numbers [in Lua 5] \endverbatim * \ingroup stats