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Colour maps

Give any image a colour map and you can click an element — a wall, a window, a mullion — to select it as a mask region instead of painting it by hand.

A colour map is a second image that tags every element in a view with its own flat colour — one colour for the floor, another for each window, another for a mullion. It is never shown to you directly. It exists so the app can answer a single question: which element did I just click?

With a colour map attached, the mask tools gain click-to-select: click a wall and its exact silhouette becomes the mask region, hover and the element under the cursor highlights. No painting, no tracing around window frames.

It works on any image, not just CAD

A Revit import can bring its colour map with it, and that is the easiest way to get one. But you can upload a colour map to any image layer — a hand-drawn plan, a diagram, a render you colour-blocked yourself. The moment a layer has one, the segmentation tool lights up in the mask toolbars and behaves exactly as it does for a CAD import.

Add, replace, remove

The colour-map control sits in the layer’s mask row in the layers panel. It shows whether the selected layer has a map, and opens the actions:

  • Upload / Replace — pick a PNG or BMP.
  • Download — get the map back as a PNG, exactly as stored.
  • Copy / Paste — copy the map from one layer and paste it onto another. Instant at any size: pasting points the second layer at the same map rather than duplicating it.
  • Remove — detaches the map from this layer only. Any other layer using the same map keeps working.

Layers inherit the map

Because a layer only points at its map, derived layers get it for free:

What you doDoes the new image have the map?
Duplicate or copy a layerYes
Generate from a layerYes — the result keeps the source’s map
File a CAD extractionYes, on the extracted layer
Merge two layersOnly if exactly one of them had a map
Text-to-image, plain upload, frame renderNo

Merging is deliberately cautious: if both layers had a colour map, neither one describes the merged pixels any more, so the result starts empty.

File requirements

A colour map is a lookup table that happens to be stored as an image, so the file rules are stricter than for a normal upload — and breaking them fails silently, producing a map that looks fine but selects nonsense.

  • PNG or BMP only. JPEG is rejected. JPEG compression shifts colours slightly across each block, so one flat-coloured element arrives as hundreds of near-identical colours — and each becomes its own phantom element.
  • Never scale a colour map in another tool before uploading. Smooth (interpolated) resizing invents in-between colours along every boundary, ringing each element with a halo of false ones. The app never interpolates for the same reason.
  • If you pad it, pad with pure white. White is the background colour; any other fill parses as one enormous bogus element.

Different size is fine. A map at a different resolution to its image needs no preparation — the app maps between them as you hover and click, losslessly. Only a different aspect ratio is adjusted, by adding white padding until the shapes agree; the map’s own pixels are copied across untouched. You will see a warning when that happens, because a framing mismatch usually means the map came from a different view than the image.

Auto-repair for shattered maps

A material-ID pass out of a renderer often arrives with hundreds of thousands of near-unique colours instead of a few dozen flat ones — anti-aliasing, per-instance colour on scattered planting, and subtle gradients all conspire. Such a file used to be rejected outright.

On upload, the app now repairs it. It works out the map’s true palette and snaps every stray colour onto the nearest real entry. On a real 3000×2400 export this turned 304,064 colours into 16 elements, visually identical at full size.

Two things to know:

  • Repair is lossy, and it tells you how lossy. The notice reports what proportion of the map was reassigned — on that same file, about a quarter, almost all of it planting merged into its surroundings. Elements that were only ever a scatter of near-unique pixels do not survive as separately selectable things.
  • Your original is kept. The unrepaired file is archived alongside the repaired one, so nothing you supplied is lost.

Repair runs on upload only. A map a layer inherited is never rewritten, since that same map may be in use by layers in other workspaces.

If click-to-select behaves oddly

  • Everything selects as one huge region — the map probably has a transparent background instead of a white one.
  • Clicking selects a sliver, or nothing — the map was likely saved as a JPEG at some point in its life, or resized with smoothing. Re-export it as a PNG at its original size.
  • The wrong element highlights — the map and the image are probably from different views. Check whether you saw a framing warning when it was uploaded.