Design · 3 min read
How Image to ASCII Art Conversion Works
ASCII art draws a picture with text characters. Converting a photo is a neat demonstration of how images are just grids of numbers.
Try it yourself with the related tool.
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Brightness to characters
The image is shrunk to a grid — say 100 columns — and each cell's brightness is measured. A ramp of characters ordered from dense to sparse, such as @%#*+=-:. , assigns a dense character to dark cells and a space to bright ones. On a dark background, reverse the ramp.
Fix the aspect ratio
Characters are about twice as tall as they are wide, so a square grid of characters looks stretched. Sample half as many rows as columns to keep proportions right.
Getting a good result
High-contrast images with a clear subject work best; busy photos turn into noise. Boost contrast before converting, crop tightly, and view the result in a monospace font — in a proportional font, the columns will not line up.