How I Dither Images to Mimic Printed CMYK Using ImageMagick
My Images Are Dithered
I share my process for dithering images to create a printed, black-and-white aesthetic with pink accents. By using ImageMagick, I simulate Amplitude Modulated (AM) print grids to avoid Moiré patterns and reduce file size. I explain the evolution from a simple monochrome method to a more accurate CMYK simulation that varies dot sizes, achieving a distinct retro look while maintaining image details.
Who said blogging about your stupid idea isn't useful?
- trentor
I was a rotogravure printer in another life, and this post made me a bit nostalgic. In intaglio printing you usually don't see these patterns because the electrostatic assist pulls the ink out of the cells, and the colors blend together more. It's more akin to a developed photo. I mainly remember them from having to do offset printing for the intermediate exam during my apprenticeship.
Our paper was about 3.5 meters wide, and a single roll length was 2–3 kilometers which ran for 20-30 minutes. The process delivered high quality at high speed, so we printed titles like Playboy and the IKEA catalogue in every language (for a language change we only had to swap the black cylinders, since the data was optimized so the text was mostly single color black). A print run of the IKEA catalogue, around 40 million copies, took about two months. It was brain numbing but also really zen. I miss it sometimes.
- AyanamiKaine
Ohhhh that is so cool, but I agree with the others its more halftoning. When you want to dither/pixelate an image you can use Image-to-Pixel [0].
- ReactiveJelly
> Dithering can reduce file size
Yeah, if you're using lossless compression like PNG or GIF, adding a lossy step to reduce the number of colors in the palette can help.
If you're compressing photos, you should use JPEG or WebP.
Anecdotally, JPEG usually beats dithering, and WebP always does.
It's fine to dither images but please please admit that you're doing it for the aesthetic. WebP has very broad browser support and absolutely blows dithering out of the water for compression. You are not going to beat years of research and tuning with "use fewer colors".
I remember a YouTube video about "How we did the impossible and got full-motion video for this Sonic game on a system that couldn't do FMVs", and the answer was like, "Well, we used a low resolution, and then we reduced the color palette, and then we cut the frame rate, and then we did interlacing." None of that's impossible! That's like saying you built the Pyramid at Giza using only a bucket of Lego bricks! It's not the same pyramid! Anyone can use a lower resolution! It takes effort and teamwork to come up with a codec that actually compresses data without artifacts!
- rahimnathwani
If you're doing halftoning with the intent to get custom DTF (direct to film) prints for t shirts, you might find this tool helpful:
It aims to 'knock out' some areas of the image: make them transparent in the digital image so those areas are not part of the final film. This means less of the surface of the t shirt has film on it, allowing it to be breathable and flexible.
I got some DTF prints made before I knew you were meant to do this. The tutorials online required a lot of steps so I made the above for next time. Not tested for real yet.
- xnx
Title here is missing "How" as in "How My Images Are Dithered"