Hello:
The issue is first noted when I tried to reproduce a specific LUT in a commercial workstation by creating a custom LUT with 10 colors, and use it in a subtracted CT volume with standardized window and level ( basically with min 0 HU and max at a certain HU ). Then I noted that the displayed color is not compatible with the window and level settings in Volumes module, most region in the volume shows the color of maximum value. I then toggle color bar in Dataprobe module, and found that while as the data probe in left lower corner shows correct value, the viewport shows the color of 20-25 times of the actual value.
This also applies to builtin color tables with less then 255 colors (e.g. DarkBrightChartColors / 64Color-Nonsemantic) and I then noted that the it shows the color of with [ 255 / color count ] times the actual value.
CT Volume in “Gery” color table:
CT Volume in custom 10-color color table (see below for color txt):
Expected color is shown when adjust color window/level to roughly 25.5X (255/10)
This issue is also reproducible with sample dataset.
I’m not sure if I’ve missed something.
Thanks for reporting. The current behavior is indeed not intuitive. We already have an issue for improving this, but for now you need to specify 0-255 range in the color table and then map it to the volume by setting the appropriate window/level in the display node. See more information here:
Hello:
Thanks for the quick and precise reply!
The workaround you provided works fine.
(upper panel: original 10 step color LUT, lower panel: 255 step workaround)