printing on a grayscale printer) and collapsed to emulate different types of color-blindness (without red-green or green-blue contrasts) using the simulate_cvd functions. choose_palette by default starts the Tcl/Tk version of the GUI while hclwizard by default starts The output is a grayscale version of the JPEG. There are many different ways to convert RGB color components to grayscale and this tool supports four ways to do it. You can use one of three grayscale formulas that are used in HDTV, Pal/Ntsc systems, or using average component formula, or you can define your own custom grayscale formula.
What you must understand is that this does not convert a grayscale image to color. that is a black and white image, remains black and white image after conversion. The only thing that changes is that, before the conversion happens, each pixel are represented as a single value, example: (120) and after conversion, it is represented in 3 channels.