retroimg

Convert images to appear to be reproduced on retro IBM hardware.

original (640x480, 24-bit RGB)	VGA (320x200, 256 colors, 4:5 pixels)	EGA (320x200, 16 colors, 4:5 pixels)	CGA (320x200, 4 colors + bkg)

The full image processing pipeline is composed of the following steps:

1. Image cropping and resizing to a low resolution;
2. Master palette color quantization and mapping to a restricted color palette, plus color limit with dithering;
3. Nearest-neighbor resizing to a high resolution, to make pixels look good, also enabling non-square pixels.

Note: This application does not claim to achieve a perfect emulation of old hardware, but it should hopefully attain sufficiently good results for the intended nostalgia kick.

Using

The main options are:

• -s | --standard: the video graphics standard to emulate. This only affects the colors used, not the image resolution. Possible options:
  • cga or cgamode4: CGA in mode 4, attempts to choose the best sub-palette and background color
  • fullcga: all 16 colors of the CGA master palette
  • cgamode4high1: CGA in mode 4, always subpalette 1 of high intensity (black, magenta, white, black)
  • ega: all 64 colors from the EGA master palette
  • 16bit: 16-bit color depth (4-5-4 RGB)
  • vga (default) or 18bit: 18-bit master palette
  • true or 24bit: 24-bit RGB color depth
• -R WxH: the resolution to resize the image into.
• -S WxH: the full image output size, resized from the previous option.

To convert an image to look like it was presented in VGA mode 13h, with non-square pixels:

retroimg «IMAGEFILE» -s vga -R 320x200 -S 1440x1080 -o «out.png»

This chooses the 256-color palette with the least loss. To use less colors (e.g. 100):

retroimg «IMAGEFILE» -s vga -R 320x200 -S 1440x1080 -c 100 -o «out.png»

To choose an output width or height and let the program pick the other dimensions based on pixel ratio:

retroimg «IMAGEFILE» -s vga -R 320x200 --height 1080 -r 4:5 -o «out.png»

This will stretch the image proportionally to the pixel size 4:5, meaning that it works best for images designed for this.

The full list of options is presented via retroimg -h or retroimg --help.

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.