SVG import: How to restrict material count to the SVG's palette colors?

Question

I did an Image Trace in Adobe Illustrator and saved it as an SVG. The trace was restricted to a palette of just 6 colors. But upon importing into Blender, I end up with a separate material for each island, which in this case is hundreds of objects titled incrementally such as SVGMat.820

Up to this point, whenever I imported SVG data into Blender, it was simpler geometry, maybe a logo or something. So I just replaced the default SVG import materials with my own, maybe sampling the hex colors where relevant, and throwing away the rest.

But this time I want to keep that palette of 6 colors and just modify the shader data (I mean send unique material colors from RGB Nodes into a shared Group Node containing the shader setup - do you follow?). Unfortunately Blender has no idea that some of those materials share a common color, while others do not. And I don't feel like pasting that Group Node into 820+ separate materials! lol

Is there a way this can be tackled using Python to loop through all materials named SVGMat.* check if the Diffuse Color matches an existing material's Diffuse Color, and if it does, discard that redundant material in favor of the existing one?

(I feel like ideally the option to restrict materials to unique colors ought to be included as a setting of the SVG importer, possibly as default, but for now any kind of scripting workaround would be awesome.)

Answer 1

Assuming you are starting with a muli-path trace result created with some vector design software such as Illustrator or Inkscape - here are the steps in Inkscape for consolidating and joining the paths of that artwork according to color:

1. Go to Layer > Layers & Objects. This gets the Layers panel to appear if it isn't already visible.

2. Create a layer for each color to keep paths in order. To make the result more intuitive, you can re-order the layers so that Layer 1, Layer 2, Layer 3, etc go from top-to-bottom instead of bottom-to-top.

^{Tip: You can re-order layers quickly by clicking the Up and Down arrow buttons at the top of the Layers panel.}

3. Select the topmost path in the group, then Edit > Select Same > Fill Color, and drag those selected paths into the topmost layer. Aim carefully to drop into the layer, not above or below it.

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^{The selected layers are now those which share the same color.}

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^{Tip: Once a layer contains something, a triangle icon appears to the left of it. You can use this to keep track of which layers you have already dragged paths into. It's a good idea to click this icon to collapse a layer to hide its contents after dragging paths into it.}

^{Tip: If you have a solid color background in your trace result that you want to get rid of, now is the time to delete that path - before joining the paths by color.}

4. Repeat step 3, selecting the topmost path, but move the selected paths to the next layer down. Do this for each path color / layer.

5. For each layer, select the range of all paths inside.

^{Note: I don't currently know of a way to select all paths in a layer in a single step, but you can select the top path and then Shift+Click the bottom path, and that whole range will be selected.}

From the menu, choose Path > Union

After doing Union, rename the path to a number indicating its position in the stack.

^{Optional: You can drag each of these paths into a single layer to consolidate / organize. You can then delete any unused layers and groups.}

6. You're done! Save As. This SVG is ready for import into Blender, and will now have a manageable number of paths, and materials to match.

_{Inkscape version used in this answer is 1.2.1 for Mac}