Colors for mappings

[daniel-wer]

This PR adds the possibility to add custom colors for mappings as well as to hide unmapped segments.
Up to 256 colors (hsv hue values) can be specified which are then used in order to color the equivalence classes of the mapping. The interface using the API is not as clean yet (see my description in https://discuss.webknossos.org/t/colors-for-mappings/602/27?u=dwerner) but as the single user of that feature will be using the json mapping interface, I think that is fine for now. We'll hopefully align the json and API mappings interface in the near future.

Note that the are now two ways that segments can end up to be transparent. If the user specifies the hideUnmappedIds flag and doesn't map a segment id, it will be transparent. Also if the user specifies not enough entries in the mappingColors array (e.g.: 3 equivalence classes, but only 2 hue values), the segments of the equivalence classes without a color will be transparent.
Thinking about it while writing this PR description, maybe it would be better to have a default color in that second case. If I remember correctly I introduced this behavior in the beginning to solve the hideUnmappedIds feature, which I solved differently now ^^

URL of deployed dev instance (used for testing):

• https://colorsformappings.webknossos.xyz

Steps to test:

• Open a tracing using the ROI2017_wkw dataset.

  • Use this user script to activate a mapping with custom colors:

  webknossos.apiReady(3).then(api => {
  	const segmentationLayerName = api.data.getVolumeTracingLayerName();
  	api.data.setMapping(
  		segmentationLayerName,
  		{ 1230341: 1, 1230557: 1, 1227259: 2, 1236582: 2 },
      	        { colors: [0.0, 0.2, 0.5], hideUnmappedIds: true }
  	);
  });

  • All unmapped ids should be transparent, and the mapped ids should have the specified colors.

• Locally, add a mapping file like this in the mappings folder of the segmentation folder of a dataset (don't forget to add the mapping name in the datasource.json):

  {
    "name": "colors",
    "classes": [[1, 2, 3], [4, 5, 6], [7, 8, 9]],
    "colors": [0.2, 0.5, 0.9],
    "hideUnmappedIds": true
  }

  • Then open a volume tracing of that dataset, brush using the ids 1, 4, and 7
  • Activate the mapping using mappings.activate("colors")
  • The respective segments should have the specified colors

• Mappings without custom colors should work as before

• Disabling/Enabling mappings should work as before

Issues:

• fixes Color for mappings #2173

---

• Updated changelog
• Updated migration guide if applicable
• Ready for review

[philippotto]

Very nice! Works like a charm 👍

• I agree that a default color should be used when there are not enough colors, but the hide-option is not set. If that's done, the PR should be ready to merge :)

[philippotto]

I hope the increased texture uniform count will not become a problem for older hardware :/ Can you test on browserstack whether iPad still works? 🙈

[daniel-wer]

Mappings will be disallowed (and the textures won't be attached, see the check a couple of lines above which is not visible here) if there are not enough textures available (Model.isMappingSupported), so this shouldn't be a problem, right?

[philippotto]

Yeah, that's right. However, the uniform is always defined in JS-land. I'm not sure whether this has implications on some systems. But probably not. We'll see :)

[daniel-wer]

The uniform "definition" is inside a if (segmentationLayer != null && Model.isMappingSupported) { check, so it should not have any implications :)

[philippotto]

segmentation

[philippotto]

MAPPING_COLOR_TEXTURE_WIDTH ** 2 is shorter :)

[philippotto]

👍

[daniel-wer]

@philippotto I applied your PR feedback, most notably a default color is now used, when there are not enough colors specified. I'd go on and merge this today :)

[philippotto]

@philippotto I applied your PR feedback, most notably a default color is now used, when there are not enough colors specified. I'd go on and merge this today :)

Nice, sounds excellent 👍