professor (forums@gimpusers.com) wrote:

I need a script that changes the opacity of a layer and then saves the whole image as a PNG file. So I wrote the following script:

#!/bin/sh

gimp -i -b -

So what am I doing wrong here?

Variables declared with a let or a let* block are only valid *inside* the block. So basically your additional let* block has no real effect in terms of variables, since you close it immediately again (It does have the side effect of merging the visible layers).

I would probably do it like this:

(let* ((image (car (gimp-file-load 1 "test.xcf" "test.xcf"))) (drawable (car (gimp-image-get-active-layer 1))) (new-layer 0))

(gimp-layer-set-opacity drawable 50) (set! new-layer (car (gimp-image-merge-visible-layers image EXPAND-AS-NECESSARY)))
(gimp-file-save RUN-NONINTERACTIVE image new-layer "test-40.png" "test-40.png") (gimp-quit 0)
)

If you want to avoid the set! (it is kind of frowned upon, but frequently makes the code easier to read and handle), you could do it like this:

(let* ((image (car (gimp-file-load 1 "test.xcf" "test.xcf"))) (drawable (car (gimp-image-get-active-layer 1))) (new-layer 0))

(gimp-layer-set-opacity drawable 50) (let* (new-layer (car (gimp-image-merge-visible-layers image EXPAND-AS-NECESSARY))) (gimp-file-save RUN-NONINTERACTIVE image new-layer "test-40.png" "test-40.png") )
(gimp-quit 0)
)

Watch how the code is nested here. The new-layer variable goes out of scope (loses its meaning) after the closing parentheses in the following line.

Note that this is untested code.

Hope this helps, Simon