GIMP Script-Fu and Python-Fu: Batch Processing and Automation Guide

; Batch resize: all images in input-dir → output-dir at max 1200px wide
; Save this file as batch-resize.scm in your GIMP scripts folder

(define (batch-resize input-dir output-dir max-width)
  (let* ((filelist (cadr (file-glob
                     (string-append input-dir "/*.png")
                     1))))
    (for-each
      (lambda (filename)
        (let* ((image (car (gimp-file-load RUN-NONINTERACTIVE filename filename)))
               (orig-width  (car (gimp-image-width image)))
               (orig-height (car (gimp-image-height image)))
               (scale (if (> orig-width max-width)
                        (/ max-width orig-width)
                        1.0))
               (new-width  (round (* orig-width scale)))
               (new-height (round (* orig-height scale)))
               (basename (car (strbreakup (car (strbreakup filename "/")) ".")))
               (outfile (string-append output-dir "/" basename "-resized.jpg")))
          (gimp-image-scale-full image new-width new-height INTERPOLATION-CUBIC)
          (gimp-image-flatten image)
          (file-jpeg-save RUN-NONINTERACTIVE image
            (car (gimp-image-get-active-drawable image))
            outfile outfile 0.85 0 0 0 0 0 0 0)
          (gimp-image-delete image)))
      filelist)))

; Call it:
(batch-resize "/home/user/photos" "/home/user/output" 1200)

; Add watermark text to all images in a directory

(define (add-watermark image watermark-text)
  (let* ((width  (car (gimp-image-width image)))
         (height (car (gimp-image-height image)))
         (text-layer (car (gimp-text-fontname
                        image -1           ; drawable (-1 = new layer)
                        20 20          ; x, y position
                        watermark-text
                        0             ; antialias
                        40            ; font size
                        UNIT-PIXEL
                        "Sans Bold"))))
    (gimp-layer-set-opacity text-layer 60)  ; 60% opacity
    (gimp-text-layer-set-color text-layer '(255 255 255))
    ; Move to bottom-right corner
    (let* ((tw (car (gimp-drawable-width text-layer)))
           (th (car (gimp-drawable-height text-layer))))
      (gimp-layer-set-offsets
        text-layer
        (- width tw 20)   ; 20px from right
        (- height th 20)))  ; 20px from bottom
    image))

; Batch convert PNG to WebP
; Requires GIMP 2.10+ with WebP support

(define (batch-png-to-webp input-dir output-dir quality)
  (let* ((filelist (cadr (file-glob
                     (string-append input-dir "/*.png") 1))))
    (for-each
      (lambda (filename)
        (let* ((image (car (gimp-file-load
                         RUN-NONINTERACTIVE filename filename)))
               (name-parts (strbreakup filename "/"))
               (basename   (car (strbreakup
                              (car (last-pair name-parts))
                              ".")))
               (outfile    (string-append output-dir "/" basename ".webp")))
          (gimp-image-flatten image)
          (file-webp-save RUN-NONINTERACTIVE image
            (car (gimp-image-get-active-drawable image))
            outfile outfile
            0        ; preset (0=default)
            quality  ; quality 0-100
            0 0 0 0 0 0)
          (gimp-image-delete image)))
      filelist)))

(batch-png-to-webp "/source" "/output" 85)

#!/usr/bin/env python3
# Python-Fu batch resize - Run from Filters → Python-Fu → Console
import os, gimp, gimpfu

def batch_resize(input_dir, output_dir, max_width):
    os.makedirs(output_dir, exist_ok=True)
    for fname in os.listdir(input_dir):
        if not fname.lower().endswith(('.png', '.jpg', '.jpeg')):
            continue
        fpath = os.path.join(input_dir, fname)
        image = gimp.pdb.gimp_file_load(fpath, fname)
        w = image.width
        h = image.height
        if w > max_width:
            scale = max_width / w
            image.scale(
                int(w * scale),
                int(h * scale)
            )
        image.flatten()
        out_name = os.path.splitext(fname)[0] + '-resized.jpg'
        out_path = os.path.join(output_dir, out_name)
        gimp.pdb.file_jpeg_save(
            image, image.active_drawable,
            out_path, out_name,
            0.85, 0, 0, 0, "", 0, 1, 0, 2, 0
        )
        gimp.pdb.gimp_image_delete(image)
    print(f"Done. Processed images saved to {output_dir}")

batch_resize("/home/user/photos", "/home/user/output", 1200)