Edge detect leaves invisible layers

[marty39]

I'm using Gimp 3.04 in macOS. I have a color photo, I desaturate and apply one of the edge-detect filters. The edges come out white on dark, I want black edges on a light background, so I invert colors. I still have white edges on a dark background but they have moved a little. It acts like there is more than one layer and I'm only inverting one of them. So I apply flatten image, and then color invert. Now I get the expected result, dark edges on a light background.

This happens with all the different edge detect filters. It did not happen in Gimp 2.x. Something changed and I want it fixed. Preferably merge those layers, as apparently happened in Gimp 2.x, or at least show the layers in the layers panel.

[sallyanne]

Looks like you checked 'merge filter'

Doesn't happen here as long as merge filter isn't checked, there is only one layer after edge detect. Then invert and all is ok.

If you want your colors reversed you can do it in the gimp plugin GMIC, under contours - 'edges' and check negative colors. Make sure you have the output as in place, if you dont want two layers


In Gimp only
   

If you want to make the grey/black darker you could try contrast/lavels/curves

Maybe don't desaturate first.

[Ofnuts]

(07-13-2025, 09:34 PM)marty39 Wrote: I'm using Gimp 3.04 in macOS. I have a color photo, I desaturate and apply one of the edge-detect filters. The edges come out white on dark, I want black edges on a light background, so I invert colors. I still have white edges on a dark background but they have moved a little. It acts like there is more than one layer and I'm only inverting one of them. So I apply flatten image, and then color invert. Now I get the expected result, dark edges on a light background.

This happens with all the different edge detect filters. It did not happen in Gimp 2.x. Something changed and I want it fixed. Preferably merge those layers, as apparently happened in Gimp 2.x, or at least show the layers in the layers panel.

You are probably having filters applied as non-destructive. Make sure you check the "merge filter" option in the filter dialog. Or click the fx icon next to the layer in the Layers list, and then the Merge active filters down icon in the popup.

[marty39]

(Yesterday, 03:17 AM)sallyanne Wrote: Looks like you checked 'merge filter'

Doesn't happen here as long as merge filter isn't checked, there is only one layer after edge detect. Then invert and all is ok.

....

Thanks. "Merge filter" was not checked. I checked it and it remains checked for all the edge detect filters, and the problam went away.

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(Yesterday, 06:02 AM)Ofnuts Wrote:

(07-13-2025, 09:34 PM)marty39 Wrote: I'm using Gimp 3.04 in macOS. I have a color photo, I desaturate and apply one of the edge-detect filters. The edges come out white on dark, I want black edges on a light background, so I invert colors. I still have white edges on a dark background but they have moved a little. It acts like there is more than one layer and I'm only inverting one of them. So I apply flatten image, and then color invert. Now I get the expected result, dark edges on a light background.

This happens with all the different edge detect filters. It did not happen in Gimp 2.x. Something changed and I want it fixed. Preferably merge those layers, as apparently happened in Gimp 2.x, or at least show the layers in the layers panel.

You are probably having filters applied as non-destructive. Make sure you check the "merge filter" option in the filter dialog. Or click the fx icon next to the layer in the Layers list, and then the Merge active filters down icon in the popup.

Thanks. "Merge filter" was not checked. I checked it and it remains checked for all the edge detect filters, and the problam went away.