PPM to Braille Art Converter

Uses some code from my image generator.

Takes input on stdin as ppm, outputs to stdout as text.

Usage:

• brailleart: No arguments: default, black background, white foreground, 0.5 threshold
• brailleart invert: Single invert argument: white background, black foreground, 0.5 threshold
• brailleart 0.3: Single double argument: black background, white foreground, given threshold
• brailleart invert 0.3: Two arguments (first invert, second double): white background, black foreground, given threshold
• No other argument formats are supported at this time.