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Using GIMP, I wish to fade an image inward from the edges, blending it with the neutral (white) background.

I have tried numerous things including feather edges, blur and Gaussian blur, but none of them produces a good result. Specifically, they all appear to blend the image outward or in both directions. I wish to fade the image inward from the edges, and without loss.

A tedious manual technique that I believe might work would be to:

  1. select the background
  2. grow the selection by 1 pixel
  3. adjust the brightness, then
  4. repeat 2. and 3. as many times as necessary

However, it strikes me that there is probably a tool that performs the same function.

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The technique that I describe above as 'tedious' proved to be less so than I had imagined. I attained a good result rather quickly by selecting the background, and progressively (one pixel at a time) growing the selection and adjusting the brightness of the selection.

Whilst I applied the same adjustment of brightness each time, one could conceivably tailor it to give different blur effects.

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  • Each time you use color/brightness you lose colors, either in the lights or in the shadows. With your technique, pixels are subject to color/brightness several times, so you can potentially lose a lot of colors. I also suspect that this technique worked for you on that pair of images, but will not work in the general case (how do you handle the case here image differ only by the hue?).
    – xenoid
    Nov 6, 2016 at 17:25
  • Yes, there are undoubtedly circumstances in which this method is limited. I am not sure what you mean about loss of colour. The use of the feather edges tool would appear to do create the same result, washing out the colour, albeit with far less trouble. By this method, one has to grade the progression of fade (on top of fade) manually. Suffice to say that there should be a better way. I think the layer mask mentioned above would be far better.
    – POD
    Nov 7, 2016 at 3:30
  • The number of distinct colors diminishes, and things that had different tones end up having the same RGB, so you create 'flat' areas, banding, etc...
    – xenoid
    Nov 7, 2016 at 8:18
  • I understand what you mean, but (forgive my ignorance) does that really happen? Perhaps the assumptions I have made with regard to the brightness function have been incorrect. My understanding has been that it raises or lowers all of the light values, hence shifting each colour closer to black or white. Provided that no colours actually reach those extremes, it is my understanding that there will be no information loss.
    – POD
    Nov 7, 2016 at 15:05
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    "Brightness" raises the black (or lowers the white) and maps the rest of the range linearly. So when you decrease the white by 20, you map your original 256 value into the remaining 236 values, so some originally distinct values assume the same output value. This is also visible in the histogram ("haircomb" histogram).
    – xenoid
    Nov 7, 2016 at 17:28

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