GIMP Script-fu

sg-expand-strip
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Command:
Expand Strip
Menu:
"<Image>/Layer/Expand Strip"
PDB Name:
script-fu-sg-expand-strip
Download:
sg-expand-strip.scm (after the page appears, click on the "Download" command)
License:
GPLv2+

Description:

The main purpose of this script is to double the size of either a horizontal or a vertical strip in a layer, repositioning the unselected regions and resizing the layer (and image, if necessary) to accommodate the expanded strip.