Blackstripes python extensions

Your drawbot will like it!

This is a python module written in c. It turns an png image into a svg line drawing. The output is very suitable for vsg capable drawbots. We use it every day on blackstripes.nl.

This also comes with a command-line interface for using it, installed at the same time as the python module. Check blackstripes --help for detailed usage.

How to use

This module exposes 3 drawing styles.

1. Sketchy

from blackstripes import sketchy

sketchy.draw("ali.png",                 # input
         	 "ali_sketchy.svg",         # output
            1,                          # nibsize (line size in output svg)
            100,                        # max line length
            "#000000",                  # line color
            0.32,                       # scaling factor
            1,                          # line size (internal line size for calculations)
            540, 1021, 0.7              # signature transform tx, ty, scale
        )

Using the CLI:

blackstripes sketchy ali.png --output ali_sketchy.svg

How does it work

1. Calculate the brightness of the input image.
2. Place the pen at pixel 0,0.
3. Get a random line length between 10 and the max segment length.
4. Evaluate 360 lines by making a 360 degree sweep with the selected line length.
5. Get the line covering the largest average darkness in the input image.
6. Draw this line white in the input image.
7. Draw this line black in the ouput image.
8. Calculate the brightness of the output image.
9. Repeat from step 2 until the brightness of the output image is equal to the inpute image.

2. Crossed

from blackstripes import crossed

crossed.draw("ali.png",             # input
        	 "ali_crossed.svg",     # output
            2.0,                    # nibsize (line size in output svg)
            "#2200aa",              # line color
            0.32,                   # scaling factor
            200, 146, 110, 56,      # levels
            2,                      # type
            540,1021,0.7            # signature transform
        )

Using the CLI:

blackstripes crossed ali.png --output ali_sketchy.svg

3. Spiral

from blackstripes import spiral

spiral.draw("ali.png",                  # input
       	    "ali_spiral.svg",           # output
            2.0 ,                       # nibsize (line size in output svg)
            "#aa0000",                  # line color
            0.32,                       # scaling factor
            180, 108, 180, 108,         # levels
            2,                          # linespacing
            540,1021,0.7                # signature transform
        )

Using the CLI:

blackstripes spiral ali.png --output ali_sketchy.svg

How to build

(This module is tested with python 2.7 and python 3.4 on mac-osx and linux, but it will probably work on most platforms.)

1. Clone this repo
2. navigate to the src folder
3. python setup.py build
4. python setup.py install
5. navigate to the test folder
6. python sketchy-test.py
7. python crossed-test.py
8. python spiral-test.py