How can I combine two images with a mask instead of a hard-edged cutout?

Use a mask on the upper image layer rather than erasing the part you do not want. A mask controls which parts of a layer remain visible, so the lower image can show through where the upper image is hidden; you can revise the mask later without permanently erasing the layer’s pixels. [S1]

A practical starting point is to align the two images, add a mask to the upper layer, and hide only the area that needs to give way to the image beneath. Work gradually around the boundary instead of trying to draw one perfect cutout. The best transition depends on the images: a soft blend may suit a gradual change in light or color, while a more defined boundary may suit a distinct object.

Think of the mask as a visibility map for the layer it belongs to. In Pixelmator Pro, black on a bitmap mask hides that part of the layer, white reveals it, and gray makes it partially transparent. [S2] So, if the upper image should disappear near one edge, paint black there; if you hide too much, paint white back in. Gray can help create a partial transition rather than an all-or-nothing boundary.

For other editors, look for a layer-mask or bitmap-mask feature and check that app’s own guidance for its controls. The black, white, and gray behavior described here is verified for Pixelmator Pro; these sources do not establish that every editor uses the same controls or terminology.

Refine the mask boundary, not the image itself. Pixelmator Pro’s documented controls include Softness, which softens mask edges, and Smart Refine, which is intended to detect details such as hair or fur. These settings affect the mask boundary rather than applying a blur filter to the image layer. [S2]

Try the adjustment on the troublesome section first, then inspect the whole composite. If an edge becomes hazy or the lower image bleeds through too far, reduce the adjustment or paint the mask back toward white or black as needed. Avoid assuming that a softer edge is always better: match the transition to the edge and lighting in your particular images. The product guidance does not specify ideal settings for every image or app version, and it notes that the interface may vary by version. [S2]

Yes. Keep the layered working file, then review the mask both close up and at the size people will normally see the image. Look for a leftover fringe, an accidental hole, an overly soft halo, or a visible seam that does not fit the scene. Toggle the upper layer’s visibility if that helps you compare the masked result with the original image; treat any change as reversible until you are satisfied.

Here is a compact pass you can reuse:

1. Confirm the two images are aligned as intended.
2. Check that the mask is attached to the upper image layer.
3. Inspect the transition at close range and at normal viewing size.
4. Correct only the problem areas, then inspect the full composite again.
5. Save the editable version before exporting a separate finished image.

This is an editing checklist, not a guarantee that a composite will look natural in every context. The cited guidance explains mask behavior and particular Pixelmator Pro controls; it does not prescribe export settings or establish identical steps for other editors.