making faded edges?

A solution to this problem was discussed on the Serif Affinity Forums ‘a few’ years ago:

Designer, windows: is there a rectangular transparency coming?

Designer, windows: is there a rectangular transparency coming? That's the question. Simple. Thank you all for your suggestions. Some don't work and I'm afraid…

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Quote from paleolith

Sounds simple, but the only way I've found to do it seems excessively heavy. I want an image's edges to fade out over a small portion of the width and height. (The reason is that the image will fill a card to the limits of my Epson ET-7750 printer -- which is capable of full bleed but not on the size cards I'm using -- and the registration is not precise enough to prevent the image from appearing non-centered. Fuzz to the rescue.)

I've done it as shown in the attached. I created four white rectangles covering the image, and for each, I made an opacity gradient on one edge, a different edge for each rectangle. The result is satisfactory, but is there a simpler method? Seems like something for Layer Effects, but I've looked through that panel and haven't found anything for my purpose.

is this helpful?

The following is simple and works okay. The drawback is that it tends to "round off" the corners where the glow effect 'doubles up', which you may not want. You can play with the various sliders and layer blend modes and see if you get the effect you want or not.

Target your pixel layer. Add a Layer FX (FX icon at the bottom of the Layers panel). Select "Inner Glow" and adjust the sliders, color of the 'glow' and blend mode to suit. You can see the 'rounding' at the corners in the screenshot below.

Another option is to create a rectangular selection with the rectangle marquee tool. Feather the selection. Invert the selection (Shift-Cmd-I), then apply a Gaussian Blur. Again, some rounding will occur at the corners.