How to work with effects in GIMP Python?

How to work with effects in GIMP Python? - Printable Version

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How to work with effects in GIMP Python? - joeyeroq - 04-02-2025

In GIMP 2 you could threshold the alpha channel (Layer > Transparency > Threshold Alpha...), in Python console equivalent was:

Code:

image = gimp.image_list()[0]

layer = image.layers[0]

# image,layer,threshold.

pdb.plug_in_threshold_alpha(image,layer,0)

In GIMP 3 Threshold Alpha has become a filter ("fx" icon next to the layer)
I can do in GIMP 3:

Code:

image = Gimp.get_images()[0]

layer = image.get_selected_layers()[0]

# Add Threshold Alpha layer fx (Layer > Transparency > Threshold Alpha...).

filter1 = Gimp.DrawableFilter.new(layer, 'gimp:threshold-alpha', 'My Threshold Alpha')

# Add Gaussian Blur layer fx (Filters > Blur > Gaussian Blur...).

filter2 = Gimp.DrawableFilter.new(layer, 'gegl:gaussian-blur', 'My Gaussian Blur')

layer.append_filter(filter1)

layer.append_filter(filter2)

But this does the filters in default settings.
How do I change the settings of the filters, for example how do i set the alpha value to 0 of 'My Threshold Alpha'?
[attachment=13334]

RE: How to work with effects in GIMP Python? - joeyeroq - 04-02-2025

I couldn't find any usefull documentation on DrawableFilterConfig methods. I googled some more found this thread on gimpchat.com GIMP 3 now has GEGL automation in python console. So to set parameters for filters you do this:

Code:

# Get image and selected layer.

image = Gimp.get_images()[0]

layer = image.get_selected_layers()[0]

# Add Threshold Alpha layer fx (Layer > Transparency > Threshold Alpha...).

filter_threshold_alpha = Gimp.DrawableFilter.new(layer, 'gimp:threshold-alpha', 'My Threshold Alpha')

To print the parameters in the console you can use DrawableFilter.get_config().list_properties():

Code:

for parameter in filter_threshold_alpha.get_config().list_properties():

    parameter.get_name(), parameter.get_default_value()

# To set the parameter to 0 you do

filter_threshold_alpha.get_config().set_property('value', 0.0)

# Append Threshold Alpha filter to the layer.

layer.append_filter(filter_threshold_alpha)

Now let's add Gaussian Blur

Code:

# Add Gaussian Blur layer fx (Filters > Blur > Gaussian Blur...).

filter_gaussian_blur = Gimp.DrawableFilter.new(layer, 'gegl:gaussian-blur', 'My Gaussian Blur')

# set properties for Gaussian Blur.

filter_gaussian_blur.get_config().set_property('std-dev-x', 5.5)

filter_gaussian_blur.get_config().set_property('std-dev-y', 5.5)

# If you set the properties after adding the filter to the layer you have to use:

filter_gaussian_blur.update()

I tried to add all properties for Gaussian Blur at once but

Code:

filter_gaussian_blur.get_config().set_properties(('std-dev-x', 1.5), ('std-dev-y', 1.5), ('filter', 'auto'), ('abyss-policy', 'clamp'), ('clip-extent', True))

and

Code:

filter_gaussian_blur.get_config().set_properties(5.5, 5.5, 'auto', 'clamp', True)

didn't work either. To merge the filters down use:

Code:

layer.merge_filters()

[attachment=13336]

How do you find out what the filter operation’s name are like 'gimp:threshold-alpha' and 'gegl:gaussian-blur' when using Gimp.DrawableFilter.new(drawable, operation_name, name)?

RE: How to work with effects in GIMP Python? - Ofnuts - 04-03-2025

Some pointers (no time to develop more that this ATM):

https://gegl.org/operations/ (there may be some more that are gimp-specific).
https://gitlab.gnome.org/GNOME/gimp/-/merge_requests/2008
https://developer.gimp.org/api/3.0/libgimp/method.Drawable.merge_new_filter.html

RE: How to work with effects in GIMP Python? - joeyeroq - 04-06-2025

Thanks to HoneyBadger at GIMP Discord:

HoneyBadger wrote 2025-04-05T06:28:14.224Z about getting the name of operations like 'gimp:threshold-alpha' and 'gegl:gaussian-blur':
You can extract the names of operations from the filters applied to the layer:

Code:

Gimp.get_images()[0].get_layers()[0].get_filters()[0].get_operation_name()

HoneyBadger wrote 2025-04-04T21:04:43.798Z about adding all properties of a filter at once in stead of one by one:
It turns out the documentation is not complete, the method really exists
You can use it like this:

Code:

config.set_properties(prop1=value1, prop2=value2)

But if the property name contains a hyphen, you will have to do it differently:

Code:

my_props = {

'std-dev-y': 3,

'std-dev-x': 3

}

config.set_properties(**my_props)

Or:

Code:

config.set_properties(**{ 'std-dev-y': 3, 'std-dev-x': 3 })

You can even mix them together if you want:

Code:

config.set_properties(filter='auto', **{ 'std-dev-y': 3, 'std-dev-x': 3 })

RE: How to work with effects in GIMP Python? - Ofnuts - 04-06-2025

In practice for a similar call I use a wrapper:

Code:

def callProcedure(procId: str, run_mode=Gimp.RunMode.NONINTERACTIVE, **kwargs):

    procedure=Gimp.get_pdb().lookup_procedure(procId)

    if procedure is None:

        raise Exception(f'Procedure "{procId}" no found')

    config: Gimp.ProcedureConfig = procedure.create_config()

    #config.set_property('run-mode',run_mode)

    for name,value in kwargs.items():

        if isinstance(value,list):

            config.set_core_object_array(name.replace('_','-'),value)

        else:

            config.set_property(name.replace('_','-'),value)

    result=procedure.run(config)

    results = [result.index(i) for i in range(result.length())]

    if results[0] is not Gimp.PDBStatusType.SUCCESS:

        raise Exception(f'Error returned from procedure "{procId}": {results[0].value_name}')

    return results[1:]

So you can call the procedure with Python keyword arguments:

Code:

   res = callProcedure('plug-in-sel2path', image=image,

                        drawables=[selectableLayers[0]],

                        align_threshold=.05,

                        corner_surround=1,

                        error_threshold=.05,

                        filter_epsilon=1,

                        filter_iteration_count=1,

                        filter_percent=0.

                        )

And the callProcedure code converts python-friendly argument names such as filter_epsilon into Gimp friendly names such as filter-epsilon.