[dahart]

I still use dithering daily with 24 bit color images. In fact, my test for whether a modern image editor is serious and good is whether it supports dithering when converting from floating point color channels down to 8 bits per channel. Photoshop does this.

The most important reason for me is not display on the monitor, but printing the image. I do a lot of large format printing, and printers smash parts of your color space and make some gradient/banding problems stick out like a sore thumb. Dithering is critical when printing!

Gradients with banding can easily show up when you resize a large image down to a smaller size. This is a good reason that resizing probably anything less than 16 bits per channel images should be done in a higher precision format than the image.

I haven't tried to use an error diffusion dither when converting 16 bits per channel down to 8... I'm not sure how much that matters. It might make a difference, and it sounds fun to code either way, but in my experience, a good random number generator suffices to make color bands vanish.