Hey cool, thanks a lot for this! 
I got an error when running it however:
I don't believe it can use the coeffs parameter.
It can use "range" and "factor" (but not "width") for HistogramRGBLevels and HistogramCMYLevels, and only "width" for HistogramRGBParade.
I found that the AviSynth previewer tends to crash with HD video (i.e., 1920x1080) with HistogramRGBParade. I found that when I reduced the width using the "width" parameter, the crashing stopped (I used width=.10). So it *might* be a good idea to include width! :\
I personally don't see a need for "factor".
"range" can be "Hide Range Overlay" check box, "width" can be number box, appearing to the right of "Show Histogram" drop down. (There's room!
)
Range should be greyed out unless "RGBLevels" or "CMYLevels" is selected. (Default is true or checked.)
Width should be greyed out unless "RGBParade" is selected. (Default is .25)
At the very least I think "width" should be included, as I found it was needed to prevent crashing on some videos in the previewer.
I got an error when running it however:
Avisynth preview error: -> Script error: the named argument "coeffs" to HistogramRGBParade had the wrong type (C:\Users\Admin\AppData\Local\Temp\tempPreviewAvisynthFile18_02_48_621_tmp.avs, line 20)I don't believe it can use the coeffs parameter.
It can use "range" and "factor" (but not "width") for HistogramRGBLevels and HistogramCMYLevels, and only "width" for HistogramRGBParade.
I found that the AviSynth previewer tends to crash with HD video (i.e., 1920x1080) with HistogramRGBParade. I found that when I reduced the width using the "width" parameter, the crashing stopped (I used width=.10). So it *might* be a good idea to include width! :\
I personally don't see a need for "factor".
"range" can be "Hide Range Overlay" check box, "width" can be number box, appearing to the right of "Show Histogram" drop down. (There's room!
)Range should be greyed out unless "RGBLevels" or "CMYLevels" is selected. (Default is true or checked.)
Width should be greyed out unless "RGBParade" is selected. (Default is .25)
At the very least I think "width" should be included, as I found it was needed to prevent crashing on some videos in the previewer.