Plotting raster images

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Pen plotters can only draw lines, typically in a single color, so getting them to reproduce a photograph is difficult. This page collects some ideas for how to plot images that are represented as a grid of colors, or a raster.

Resources

Stippling

Stippling puts more points in darker regions of an image.

Line density

This system puts more discrete lines in darker regions, and includes approaches like cross-hatching.

Line deviation

One way a plotter can generate a darker region is to deflect the pen’s movement when entering a shaded area and add more lines in darker areas.

Thickness-based

These approaches rely on changing the thickness to represent density and shading. A pen plotter usually cannot vary the thickness of the lines it draws, so these will need modification to work for plotting.

Artistic

These techniques compromise the faithful reproduction of the image for artistic purposes.

Image vectorization

Vectorizing raster images is a bit more loose than techniques which can only target pen plotters, but there might be useful techniques to glean from these approaches.