Gimp Automating Image Processing with Python Fu // First Mission

What a large volume of adventures may be grasped within the span of his little life by him who interests his heart in everything.

~ Laurence Sterne.

Hi guys, one night I decided to create an online store and sell some drop ship products. The plan sounded simple: grab some pictures from the wholesale seller, customize them with a bit of store branding, and put them up for sale. The part I did not plan for was the volume.

There were a hundred images that I wanted to customize. By hand it would take ages, so I decided to create a batch script. My first thought was to use Gimp (an open source image manipulator) and Script-Fu, its native scripting language. After trying out what the result would be on the Python-Fu console, I settled with Python instead. It was a simple design, but I was satisfied, and more importantly, it was repeatable.

Here is the script that I use. Try it out on the Python-Fu console and call it convert_to_poster(n), where n is the image number in the image list inside Gimp. You could for loop it for faster batch processing.

🧪 The Script, Step by Step

First we set the variables. We grab the current image from Gimp’s image list, compute its center, and decide on a fixed canvas size of 600 by 600 pixels. The c_size_d is simply half of that size, which we will use to center the canvas crop:

current_image = gimp.image_list()[n]
center_x = current_image.width / 2
center_y = current_image.height / 2
c_size = 600
c_size_d = c_size / 2

Then we resize the image and canvas. This squeezes whatever dimensions the source photo had into our uniform 600 by 600 square, using the offsets to keep the original centered:

pdb.gimp_image_resize(current_image, c_size, c_size, c_size_d - center_x, c_size_d - center_y)

We create an empty background layer and just fill it with white. Every poster needs a solid base, and white keeps the branding readable:

bg_layer = pdb.gimp_layer_new(current_image, c_size, c_size, RGBA_IMAGE, "bg", 100, LAYER_MODE_NORMAL)
pdb.gimp_drawable_fill(bg_layer, FILL_WHITE)
pdb.gimp_image_add_layer(current_image, bg_layer, 1)

We will also set the main background and foreground color that would be used in future instruction sets. Indigo foreground, black background, these two colors are the whole brand palette:

pdb.gimp_context_set_foreground("#960acc")
pdb.gimp_context_set_background("#000000")

Create a branding layer and fill the rectangular region with indigo. This draws the colored band at the top of the poster where the text will eventually live:

branding_layer = pdb.gimp_layer_new(current_image, c_size, c_size, RGBA_IMAGE, "branding", 100, LAYER_MODE_NORMAL)
pdb.gimp_image_add_layer(current_image, branding_layer, 1)

pdb.gimp_selection_none(current_image)
pdb.gimp_image_select_rectangle(current_image, CHANNEL_OP_ADD, 0, 0, c_size, 260)
pdb.gimp_drawable_edit_fill(branding_layer, FILL_FOREGROUND)

Get the poster image and resize its layer to fit the canvas. The add_alpha call makes sure the layer supports transparency before we stretch it:

poster_layer = current_image.layers[0]
pdb.gimp_layer_add_alpha(poster_layer)
pdb.gimp_layer_resize_to_image_size(poster_layer)

Select non-alpha on the poster layer and grow. Growing the selection by 3 pixels gives us a slight edge outside the photo, which makes the next step look deliberate instead of accidental:

pdb.gimp_image_select_item(current_image, CHANNEL_OP_REPLACE, poster_layer)
pdb.gimp_selection_grow(current_image, 3)

Create a mask and fill it with the background color that we set. This creates a subtle black outline around the photo, separating it from the white base:

mask = pdb.gimp_layer_create_mask(branding_layer, ADD_MASK_WHITE)
pdb.gimp_layer_add_mask(branding_layer, mask)
pdb.gimp_layer_set_edit_mask(branding_layer, 1)
pdb.gimp_drawable_edit_fill(mask, FILL_BACKGROUND)

Add a text node with the color set to white. The store name goes on the indigo band, and the font is one that ships with the system:

pdb.gimp_context_set_foreground("#ffffff")
text_layer = pdb.gimp_text_fontname(current_image, None, 10.0, 10.0, "Psyche Digital", 0, 1, 24.0, PIXELS, "SF Compact Display Heavy")

We select the main layer and add a legacy drop shadow. That soft shadow behind the photo is what makes the poster feel like it has depth instead of looking like a flat collage:

pdb.gimp_image_select_item(current_image, CHANNEL_OP_REPLACE, poster_layer)
pdb.script_fu_drop_shadow(current_image, poster_layer, 10.0, 10.0, 10.0, (0, 0, 0, 255), 80, 0)

📜 The Full Script

Here is the full script code, all the pieces we walked through as one function:

def convert_to_poster(n):
    current_image = gimp.image_list()[n]
    center_x = current_image.width / 2
    center_y = current_image.height / 2
    c_size = 600
    c_size_d = c_size / 2 
    
    pdb.gimp_image_resize(current_image, c_size, c_size, c_size_d - center_x, c_size_d - center_y)

    bg_layer = pdb.gimp_layer_new(current_image, c_size, c_size, RGBA_IMAGE, "bg", 100, LAYER_MODE_NORMAL)
    pdb.gimp_drawable_fill(bg_layer, FILL_WHITE)
    pdb.gimp_image_add_layer(current_image, bg_layer, 1)

    pdb.gimp_context_set_foreground("#960acc")
    pdb.gimp_context_set_background("#000000")
    
    branding_layer = pdb.gimp_layer_new(current_image, c_size, c_size, RGBA_IMAGE, "branding", 100, LAYER_MODE_NORMAL)
    pdb.gimp_image_add_layer(current_image, branding_layer, 1)

    pdb.gimp_selection_none(current_image)
    pdb.gimp_image_select_rectangle(current_image, CHANNEL_OP_ADD, 0, 0, c_size, 260)
    pdb.gimp_drawable_edit_fill(branding_layer, FILL_FOREGROUND)

    poster_layer = current_image.layers[0]
    pdb.gimp_layer_add_alpha(poster_layer)
    pdb.gimp_layer_resize_to_image_size(poster_layer)

    pdb.gimp_image_select_item(current_image, CHANNEL_OP_REPLACE, poster_layer)
    pdb.gimp_selection_grow(current_image, 3)

    mask = pdb.gimp_layer_create_mask(branding_layer, ADD_MASK_WHITE)
    pdb.gimp_layer_add_mask(branding_layer, mask)
    pdb.gimp_layer_set_edit_mask(branding_layer, 1)
    pdb.gimp_drawable_edit_fill(mask, FILL_BACKGROUND)

    pdb.gimp_context_set_foreground("#ffffff")
    text_layer = pdb.gimp_text_fontname(current_image, None, 10.0, 10.0, "Psyche Digital", 0, 1, 24.0, PIXELS, "SF Compact Display Heavy")

    pdb.gimp_image_select_item(current_image, CHANNEL_OP_REPLACE, poster_layer)
    pdb.script_fu_drop_shadow(current_image, poster_layer, 10.0, 10.0, 10.0, (0, 0, 0, 255), 80, 0)

Run this code in the Gimp console or in the Script-Fu console.

🧠 Final Thoughts

That night I learned the most valuable lesson in automation: the first hour you spend writing the script is an hour that repays itself a hundred times over. A hundred images, one loop, zero boredom. If you ever find yourself doing the same image edit more than three times, stop and write a script, future you will be grateful.

🥰😝😜😁😎

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