A Quick GIMP Script to ‘Pop’ an Image

Make it pop

Background

For one my my recent Subscriber Crowns I had the need to quickly ‘enhance’ some images for a slideshow- make them a bit more vibrant. Something like the following:

I had 25 images to go through so doing each manually would have been a tedious waste of time. My two options for doing the enhancements that I wanted — saturation, contrast and brightness, and sharpening — were GIMP and imagemagick. I’ve used both for many years so either would have sufficed. I went for GIMP as I tried out the enhancements manually on one image so I knew what I was aiming for.

GIMP Batch

Thankfully, GIMP has a useful tutorial for its batch mode, called ‘GIMP Batch Mode’. I should probably go for obvious, descriptive names myself more often.

it mentions one of the important parts of any batch process, which is to be able to operate on a (globbed) file list:

You might want to apply an effect to a number of files, typically to a set of files in the same directory. GIMP 2.2 added a very useful function for this purpose, the file-glob plug-in. This turns GIMP into a versatile batch processor.

Gib Teh Codes

Since you asked so nicely, here’s what I went with in end. Bonus version for using with GIMP session, comments afterwards:

; satcontrsharp -- give image a little 'pop'

(define
  (script-fu-satcontrsharp image drawable)
  (gimp-image-undo-group-start image)
  (gimp-drawable-hue-saturation drawable 0 0 0 50 0) 
  (gimp-drawable-brightness-contrast drawable 0.039 0.051) 
  (plug-in-unsharp-mask RUN-NONINTERACTIVE image drawable 3 0.5 0)
  (gimp-image-undo-group-end image)
  (gimp-displays-flush))

(define 
  (batch-satcontrsharp pattern) 
  (let* 
    ((filelist (cadr (file-glob pattern 1)))) 
    (while (not (null? filelist)) 
           (let* ((filename (car filelist)) 
                  (image (car (gimp-file-load RUN-NONINTERACTIVE filename filename))) 
                  (drawable (car (gimp-image-get-active-layer image)))) 
             (script-fu-satcontrsharp image drawable)
             (gimp-file-save RUN-NONINTERACTIVE image drawable filename filename) 
             (gimp-image-delete image)) 
           (set! filelist (cdr filelist)))))

(script-fu-register "script-fu-satcontrsharp"
                    "Saturation-Contrast-Sharpness"
                    "Enhances image by boosting saturation, brightness+contrast and sharpness"
                    "bertieb"
                    "bertieb"
                    "2022-02-27"
                    "RGB*"
                    SF-IMAGE    "Image" 0
                    SF-DRAWABLE "Drawable" 0)

(script-fu-menu-register "script-fu-satcontrsharp"
                         "<Image>/Filters/RH")

Some observations:

• the first define sets up the common function which we can call from the batch version, or GIMP GUI
• the second is our batch function, based off the example given in the tutorial
• the script-fu-register is needed to make the function available from GIMP GUI
  • you can at present register straight to a menu entry but that is deprecated and will be an error in 3.0
  • I found out through trial and error that omitting the seventh parameter — types of images the script works on — prevents you quickly re-running the script via Ctrl+F (rerun last filter with the same settings)
• the last script-fu-menu-register registers a menu entry; I popped this one in a submenu under filters with some other filters I have written (in python)
• this could be improved in a few ways- one enhancement I’ll probably do is to add different levels of enhancement, eg ‘weak/medium/strong’

Enjoy!