How to create Photoshop layer masks from pixel data in UXP plugin (Lab Color Mode)?

Photoshop UXP Plugin API
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1

Problem

I’m developing a Photoshop UXP plugin that needs to create Lab Fill Layers with masks based on arbitrary pixel data (Uint8Array with 0-255 values). Geometric selections work perfectly, but I cannot convert custom pixel data into masks.

Environment:

  • Photoshop UXP Plugin (API version without putSelectionFromPixels())
  • Document mode: Lab Color
  • Target: Fill Layers (contentLayer/solidColorLayer) with masks from pixel data

What Works

This approach using geometric selections works flawlessly:

// Create geometric selection
await doc.selection.selectEllipse(bounds, constants.SelectionType.REPLACE);

// Create Fill Layer + mask in one call
await action.batchPlay([
{ “_obj”: “make”, “target”: { “_ref”: “contentLayer” }, “using”: { /* solidColorLayer */ } },
{ “_obj”: “make”, “new”: { “_class”: “mask” }, “using”: { “_enum”: “userMaskEnabled”, “_value”:
“revealSelection” } }
], { “synchronousExecution”: true });

Result: Perfect mask - circle visible, rest masked.

What I Need

Convert this to a mask:

const maskData = new Uint8Array(width * height);
// Populate with 255 (visible) or 0 (masked)
for (let i = 0; i < maskData.length; i++) {
maskData[i] = /* calculation */ ? 255 : 0;
}

Failed Approaches

  1. Direct mask write with imaging.putPixels({targetMask: true})
    • Tried Grayscale and Lab formats
    • Error: “target sheet is not a pixel sheet” (Fill Layers don’t support this)
  2. Temp layer + Color Range selection
    • Write pixel data to temp layer, use Color Range to select white pixels
    • Problem: Selects everything - resulting mask is all white
  3. Temp layer + transparency selection
    • Load transparency as selection
    • Problem: Same result - selects everything
  4. imaging.putSelectionFromPixels()
    • Error: API doesn’t exist in my UXP version

Question

How can I convert Uint8Array pixel data into a layer mask for a Lab Fill Layer in Photoshop UXP?

I need one of these solutions:

  • Convert pixel data → selection → use working revealSelection approach
  • Write pixel data directly to Fill Layer’s mask
  • Alternative workflow that achieves the same result

The revealSelection approach works perfectly with geometric selections - I just need to create selections from pixel data instead.

2

Does this works on RGB? If so, you could temporary change it to RGB, do the mask thing and then convert back to LAB. Proper solution? I dunno but it’ll be a workaround to make it work so you can move on with your development and not get stuck on that.

3

Doesn’t work in RGB mode either.

4

I made a solution that works both RGB and LAB:

I splitted the code into two blocks so we can see the colors as If I paste it in one block it shows up white I dunno why, but here’s it is, try it out, it worked for me:

await createMaskFromAlphaBuffer();

async function createMaskFromAlphaBuffer(alphaBuffer) {
   await executeAsModal(async () => {
     const doc = app.activeDocument;
     const docW = doc.width;
     const docH = doc.height;

     // alphaBuffer goes here... Make sure it is the size of your document
     // you can override the new Uint8Array()... if you pass a Uint8Array here
     const pixels = new Uint8Array(docW * docH); 

     for (let i = 0; i < pixels.length; i++) {
        pixels[i] = 255// White pixels just to have something, Add your mask pixels here / computation...
     }


    const options = {
        width: doc.width,
        height: doc.height,
        components: 1,
        colorProfile: "Dot Gain 20%",
        colorSpace: "Grayscale"
    }

    const imageData = await imaging.createImageDataFromBuffer(pixels, options);
    await imaging.putLayerMask({
        imageData: imageData,
        documentID: app.activeDocument.id,
        layerID: app.activeDocument.activeLayers[0].id,
        commandName: "Save Pixels in layer"
    });

    await core.redrawDocument({ documentID: doc.id });
     imageData.dispose(); // Release memory before garbage collector to speed up things

}
5

Thank you so much. This is exactly what I need. I will be trying it out later today.

Thanks for the suggestion! I am not able to make it work. Maybe I am missing something. imaging.putLayerMask() does not exist in Photoshop UXP - attempting to call it throws “Error: Unsupported napi type”.

I also tested imaging.putPixels({ targetMask: true }) which DOES exist, but it only works on pixel layers. When you try to write mask data to a Fill Layer (which is a procedural/adjustment layer, not a pixel buffer), it fails with “Error: target sheet is not a pixel sheet”.

The only working approach I found for Fill Layers with custom masks is the selection-based method:

  1. Create temp pixel layer with RGBA data (alpha channel = mask)
  2. Load transparency as selection (batchPlay “set selection to transparencyEnum”)
  3. Delete temp layer
  4. Create Fill Layer + mask in single batchPlay call using revealSelection
  5. Clear selection

This works because revealSelection is part of Photoshop’s native selection-to-mask workflow, which works on all layer types. It’s slower (~500-800ms per layer due to temp layer creation), but it’s reliable.

Tested in Photoshop 2025.x, UXP API v2.

6

I did the code with the latest Photoshop version, if you stick to the latest PS version you’ll make sure to have all the API features to date.

I did it on PS 2026 ( v27.2.0 )