In order to change the "gimp-comment" you must change a parasite that is attached to the image. The following code defines a function that will set the 'gimp-comment' parasite to the passed string. (Note: I don't have access to the GIMP right now, so I haven't tested it; though I think it will work.)

Include the function definition in your file (I recommend inserting it right after the '(define (batch-test pattern)' line) and replace your

(set! gimp-comment "Some Test Text")

with

(add-comment image "Some Test Text")

;;---------------------------------------------------------- ;; 'add-comment' attaches "gimp-comment" parasite to 'image' ;; with the value of the passed 'string' ;;
(define (add-comment image string) (*catch 'errobj
(gimp-image-parasite-find image "gimp-comment") (if (not (null? errobj))
(gimp-image-parasite-detach image "gimp-comment") )
)
(gimp-image-parasite-attach (list "gimp-comment" 3 (bytes-append string))) )

----------------------------------- Quoting David Woodfall :

Hi,

I'm trying to write a batch scm to insert a comment into a tiff. Here is the test code. It appears to function correctly but does not seem to add the comment:

(define (batch-test pattern) (let* (
(filelist (cadr (file-glob pattern 1))) (filename2)
(filename)
(image)
(drawable)
)
(while filelist
(set! filename (car filelist)) (set! image (car (file-tiff-load RUN-NONINTERACTIVE filename filename)))
(set! drawable (car (gimp-image-flatten image))) (set! gimp-comment "Some Test Text") (file-tiff-save RUN-NONINTERACTIVE image drawable "test.tif" "test.tif" 0)
(gimp-image-delete image)
(set! filelist (cdr filelist)) )
)
)

I have no idea if (set! gimp-comment "Some Test Text") is the right way of doing this but googling doesn't shed much light on it.

OOPS! The 'if' statement should be "(if (null? errobj)". I had my logic backwards.

Quoting saulgoode@flashingtwelve.brickfilms.com:

;;---------------------------------------------------------- ;; 'add-comment' attaches "gimp-comment" parasite to 'image' ;; with the value of the passed 'string' ;;
(define (add-comment image string) (*catch 'errobj
(gimp-image-parasite-find image "gimp-comment") (if (not (null? errobj))
(gimp-image-parasite-detach image "gimp-comment") )
)
(gimp-image-parasite-attach (list "gimp-comment" 3 (bytes-append string))) )

Hi,

On Sun, 2007-06-03 at 20:37 -0400, saulgoode@flashingtwelve.brickfilms.com wrote:

;;---------------------------------------------------------- ;; 'add-comment' attaches "gimp-comment" parasite to 'image' ;; with the value of the passed 'string' ;;
(define (add-comment image string) (*catch 'errobj
(gimp-image-parasite-find image "gimp-comment") (if (not (null? errobj))
(gimp-image-parasite-detach image "gimp-comment") )
)
(gimp-image-parasite-attach (list "gimp-comment" 3 (bytes-append string))) )

Why do you detach the parasite first? Shouldn't it be sufficient to just attach the new one? If I remember correctly, that should replace a parasite if one already exists under that name.

Sven