A script to capture a screenshot from the framebuffer (using fbgrab) and recolor white pixels to look like the display on the LEGO MINDSTORMS EV3.

capture-docs-screenshot.py

#!/usr/bin/env python3

# Import system utilities
import sys
from subprocess import call
# Import imaging library to resize and recolor the screenshot
from PIL import Image

# Choose the name for the screenshot to save. It defaults to "screenshot.png",
# but you can supply a custom name as a command-line argument.
out_name = sys.argv[1] if len(sys.argv) > 1 else "screenshot.png"

# Call the fbgrab utility to have it save a screenshot
call(["fbgrab", out_name]);

# Load the screenshot that fbgrab saved so that we can modify it
image = Image.open(out_name)
# Convert the black-and-white screenshot (where each pixel is just "black" or "white")
# to an image with red, green and blue channels. This lets us make it more colorful later.
image = image.convert("RGB")
# Resize the image to be twice the dimensions, making sure to preserve crisp edges
image = image.resize(tuple(i * 2 for i in image.size), Image.NEAREST)

# Get access to the underlying pixel data so that we can modify it
pixel_data = image.load()

# Loop through each pixel
for y in range(image.size[1]):
    for x in range(image.size[0]):
        # If the pixel is white, make it #adb578 (the color we
        # use as an approximation of the LCD screen) instead
        if pixel_data[x, y] == (255, 255, 255):
            pixel_data[x, y] = (173, 181, 120)

# Save the image again
image.save(out_name);