cablet

Camera track the tip of a pen to use as a drawing tablet

Setup

You will need:

Writing utensil with a colored tip (preferably blue or green)
Background that contrasts with the colored tip
Webcam

Download either the compiled executable from the releases page, or the source code (needs opencv, numpy and win32api).

Position the webcam so that as much of the colored tip is visible at all possible positions. It can also be helpful to lower the camera's exposure time (reduces motion blur).

You can change settings in settings.ini

screen_width, screen_height: Your screen resolution
camera_index: Which camera to use, 0 being the first camera
color_lower_bound, color_upper_bound: If the color of a pixel is between these two colors, it will be tracked. Format: HSV, 0-179, 0-255, 0-255
dilate_iterations: How much to scale down the mask, helps with reducing background interference, at the cost of reducing tracking resolution
contouring: Whether or not to check for the biggest group of pixels, generally leave this on
interp: How much to interpolate the cursor position (0 for off)
noshake: Don't move the cursor unless it's moved this much (camera pixels)

Don't change anything in the calibration section, these are set automatically by the program.

After running the program, you need to calibrate:

press C once to begin the process
Position the pen at the top-left corner of your drawing area and press C again
Repeat step 2 for the other three points (top-right, bottom-left, bottom-right)

Finally, you can press E to enable output to mouse.

To exit, you can click on the X button, press Q, or if things really go wrong, opening Task Manager will stop the mouse output.