Python-fu: How to batch process color-to-alpha and opacity threshold

Question

I'm trying to batch process images in GIMP 2.10 using a Python-Fu script. The script should apply the following transformations to each image in a folder:

• color to alpha with RGB value (246, 246, 246)
• transparency threshold of 0.035
• opacity threshold of 1.000 The processed images should be saved to a different folder.

I'm using the following code:

#!/usr/bin/env python

from gimpfu import *
import os

def batch_process_color_to_alpha_opacity_threshold(input_folder, output_folder):
    """
    Batch process images in input_folder and save them in output_folder after applying color to alpha and opacity threshold
    """
    # Make sure output folder exists
    if not os.path.exists(output_folder):
        os.makedirs(output_folder)

    # Loop over files in input folder
    for filename in os.listdir(input_folder):
        # Open the image
        input_path = os.path.join(input_folder, filename)
        image = pdb.gimp_file_load(input_path, input_path)

        # Get the layer
        layer = pdb.gimp_image_get_active_layer(image)

        # Apply color to alpha
        pdb.gimp_layer_add_alpha(layer)
        pdb.gimp_color_to_alpha(layer, (246,246,246))

        # Apply transparency threshold
        pdb.plug_in_transparency_threshold(image, layer, 0.035, 0.0, 1.0)

        # Apply opacity threshold
        pdb.plug_in_opacity_threshold(image, layer, 1.0, 0.0, 1.0)

        # Save the processed image
        output_path = os.path.join(output_folder, filename)
        pdb.gimp_file_save(image, layer, output_path, output_path)

        # Close the image
        pdb.gimp_image_delete(image)

    pdb.gimp_quit(0)

# Register the script with GIMP
register(
    "python_fu_batch_process_color_to_alpha_opacity_threshold",
    "Batch process images with color to alpha and opacity threshold",
    "Batch process images in a folder with color to alpha and opacity threshold, and save them in a different folder.",
    "Author Name",
    "Author Name",
    "2023",
    "<Toolbox>/Filters/Batch Process Color to Alpha and Opacity Threshold",
    "*",
    [
        (PF_DIRNAME, "input_folder", "Input folder", "C:/folder"),
        (PF_DIRNAME, "output_folder", "Output folder", "C:/folder2"),
    ],
    [],
    batch_process_color_to_alpha_opacity_threshold,
)

# Start the script
main()

After I put the python file containing the code above in GIMP plug-ins, and apply the script in the python console in GIMP, I automatically get this line in the console : pdb.python_fu_batch_process_color_to_alpha_opacity_threshold(input_folder, output_folder))

But this error occurs:

Traceback (most recent call last):
  File "<input>", line 1, in <module>
RuntimeError: execution error

And at the same time, a pop-up appears:

Calling error for procedure 'gimp-procedural-db-proc-info':
Procedure 'gimp-color-to-alpha' not found

I already checked that the GIMP Python plug-ins directory is set up correctly. I also ran a different GIMP Python plug-in to see if the issue is specific to my script, and it worked fine.

Can someone please help me figure out what's wrong with my code?

Answer 1

If you start the Python console, Hit "Browse..." and search "alpha", you will find that you are not using the right call:

Also:

• Painting a layer in Color erase mode with the color to erase does the same as Color to alpha
• You don't need to register your script as a plugin