BMP2Sixel
Convert BMP images into Sixel images
This is a console application but also has an optional GUI interface.
Converts a BMP with 256 colors or less into the Sixel format. Sixel supports a maximum of 256 colors although many terminals only support 16 colors. If your BMP has more than 256 colors, or fewer colors but uses greater than 8 bits per pixel, reduce the color count using a program like IrfanView and "Decrease Color Depth".
This program and its older brother PCX2SIX (circa 1995) are responsible for many of the Sixel images floating around the internet today.
The original BMP2SIX program written April 2001, now is updated to compile under PellesC, and provides a GUI interface. BMP2SIX output examples can be found on SourceForge under the SixelViewer program at this location, https://sourceforge.net/projects/sixelviewer/files/Sixel_Pics/
Release date 10/31/2022 version 1.2 adding Sixel HLS as an output option