09-21-2020, 07:51 PM
Good panorama stitching uses non-trivial deformations where the individual images overlap, so I doubt that you could work on individual images first. Depending on how accurate you want the mask to be, you could create a foreground selection on a smaller image and then copy it to size tot the initial image, something like this:
1) Scale a copy of the image by a factor of two (or three, or four, depending on accuray and CPU/RAM). This divides the number of pixels by 4 (or 9, or 16...).
2) Use the foreground select on the scaled down copy
3) Select>Save to channel to save the foreground selection to a channel
4) Scale back the image to its original size, this will scaled up the selection you did
5) Open the Channels list, and drag the saved selection channel to the canvas of the original image. This will create a B&W layer on that image
6) Select the initial image, an din the channels list, drag any of the R/G/B layers (that should all be your foreground selection) to the channels list below. This will copy it.
7) Reselect the channel that you dragged (because selecting it for dragging had the side effect of deselecting it). If you omit this step, you won't alter the value of that channel in your later edits, leading to funky color results.
8) Right click the copied channel, and Channel to selection
9) In the Layers list you can delete the dropped layer
1) Scale a copy of the image by a factor of two (or three, or four, depending on accuray and CPU/RAM). This divides the number of pixels by 4 (or 9, or 16...).
2) Use the foreground select on the scaled down copy
3) Select>Save to channel to save the foreground selection to a channel
4) Scale back the image to its original size, this will scaled up the selection you did
5) Open the Channels list, and drag the saved selection channel to the canvas of the original image. This will create a B&W layer on that image
6) Select the initial image, an din the channels list, drag any of the R/G/B layers (that should all be your foreground selection) to the channels list below. This will copy it.
7) Reselect the channel that you dragged (because selecting it for dragging had the side effect of deselecting it). If you omit this step, you won't alter the value of that channel in your later edits, leading to funky color results.
8) Right click the copied channel, and Channel to selection
9) In the Layers list you can delete the dropped layer