Image dithering..

[Anon]

How can you dither a image on the fly....

[Anon]

Well, you need the original image with all of its original colors.

Then you need to know what you want to dither the image to, 16bits, or 256 colors? Or, you may have a specific palette in mind, like the 216 color internet palette.

Once you have those two things, you could use the standard ordered-dither or error-diffusion-dither algorithms to dither the image on the fly (optimized implementations of these two algorithms are quite fast).

[Anon]

Let's take an example, say, we have a JPEG image which we've loaded using ImageCreateFromJPEG(); and I'd like to convert it to black and white, (with the intent of dumping it out with ImageWBMP() )

I believe this to be a useful example for discussion of dithering techniques; especially as it's a problem I'm currently trying to solve :o)