How to apply identical color curves to many pictures in GIMP?

Question

I have a few thousand images that I want to apply the exact same color curve adjustment to. Is there a way to do this in GIMP? I found this How can I get a uniform white balance on a batch of JPEG images? but this is for automatic levels adjustment rather than applying the same adjustment to every image, and I do not understand what it is or how to modify it.

I've saved a preset adjustment in "Adjust Color Curves" in GIMP, but how do I apply this to every image other than just going through everyone and clicking on it?

Answer 1

For anyone else wanting to do this I figured it out.

First I got the color curve I wanted, and clicked the plus to "Save the current settings as named preset"

Then next to the plus I pressed Manage presets -> export current settings to file

Then I downloaded CurveBatch from here http://gimpfr.org/contrib_photolabo.php

Then in GIMP I clicked edit->Preferences->Folders->Plug-ins to find where plug-ins are saved.

I then saved CurveBatch here after extracting it.

Then for GIMP 2.10 I had to change the CurveBatch plug-in (photolab_curvebatch) slightly

I changed

  if lines[0] == "# GIMP curves tool settings\n":

to

  if lines[0] == "# GIMP 'Curves' settings\n":

As GIMP 2.10 changed the first line that indicates it is a curve file (Why anyone would think for a second to do this and break backwards compatibility for no reason I do not know)

Then I pressed Filters -> Script-fu -> refresh scripts

Then I closed GIMP and reopened it.

Then the script now showed up in filters, I pressed Filters->PhotoLab->Batch corrections->curve

I chose the folder my images are in, their extension and the curve file that I exported previously.

This then applied the curves to all of my pictures as I wanted.

Answer 2

To apply curves on all images:

1. Copy this GIMP python-fu script:

#!/usr/bin/env python
from gimpfu import *
def curves_in_all_images(dummy_image, dummy_drawable, in_1, out_1, in_2, out_2, in_3, out_3, in_4, out_4, in_5, out_5):
    pdb.gimp_context_push()
    # Get the list of all opened images
    images = gimp.image_list()
    image_number = len(images)
# Loop through each image
for i in range(image_number):
    current_image = images[i]
    pdb.gimp_progress_update((i * 1.0) / image_number)
    pdb.gimp_progress_set_text("Processing image #" + str(i + 1) + " over " + str(image_number) + "...")

    # Remember the image type
    mode = current_image.base_type

    if mode != RGB:
        pdb.gimp_convert_rgb(current_image)
    current_drawable = current_image.active_layer

    # Curve the layer
    points = [in_1, out_1, in_2, out_2, in_3, out_3, in_4, out_4, in_5, out_5]
    pdb.gimp_curves_spline(current_drawable, HISTOGRAM_VALUE, len(points), points)

    #if mode == INDEXED:
        #pdb.gimp_image_convert_indexed(current_image, NO_DITHER, MAKE_PALETTE, 256, FALSE, FALSE, '')
    #elif mode == GRAY:
        #pdb.gimp_image_convert_grayscale(current_image)

    # Save the image file
    filename = pdb.gimp_image_get_filename(current_image)
    pdb.gimp_file_save(current_image, current_drawable, filename, '?')

# Refresh the image to see the changes
pdb.gimp_context_pop()
pdb.gimp_displays_flush()


Define the parameters for the script
register(
    "python_fu_curves_in_all_images",
    "Curves on all images",
    "Curves on all images and save; identical values will be ignored",
    "Fabrice TIERCELIN",
    "Fabrice TIERCELIN",
    "2024",
    "<Image>/Filters/Colors/Curves on all images",
    "*",
    [
        (PF_FLOAT, "in_1", "In 1", 0.0),
        (PF_FLOAT, "out_1", "Out 1", 0.0),
        (PF_FLOAT, "in_2", "In 2", 0.0),
        (PF_FLOAT, "out_2", "Out 2", 0.0),
        (PF_FLOAT, "in_3", "In 3", 0.0),
        (PF_FLOAT, "out_3", "Out 3", 0.0),
        (PF_FLOAT, "in_4", "In 4", 0.0),
        (PF_FLOAT, "out_4", "Out 4", 0.0),
        (PF_FLOAT, "in_5", "In 5", 255.0),
        (PF_FLOAT, "out_5", "Out 5", 255.0),
    ],
    [],
    curves_in_all_images
)
Main function
main()

2. Paste it into a text file
3. Save it with a .py extension
4. Put this file on your C:\Users\YourName\AppData\Roaming\GIMP\2.10\plug-ins folder (more information below if it doesn't work)
5. Start GIMP
6. Open all your image files by drag and drop
7. Go on Filter → Colors → Curves on all images
8. Fill as many points as you need between the 5 ones; leave those useless
9. Launch the script → all the files are already saved with the curves applied
10. Quit GIMP ignoring the prompts

For systems other than Windows, look at the settings in GIMP:

1. Click on Edit
2. Click on Preferences
3. Go on left pane; at bottom
4. Click on Folders
5. Click on Plug-ins
6. Click on Add a new folder

Successfully tested on GIMP 2.10.36 on Windows 10.

PS: If you need more points, you can easily edit the script. Then restart GIMP.