Legacy ImageMagick Discussions Archive

How come when I take an 24-bit grayscaled image (65 kb), and apply the following command to it:

convert a.bmp +dither -colors 256 a.bmp

I get a file that's 3.21kb? And when I use that file for another program, the other program doesn't accept the image as an input because it's an "unsupported bmp"?

The readme for that other program says that it will ONLY accept "uncompressed plain BMP formats".

So what do I do?

Thanks.

When you reduced the number of colors it becomes an 8bit BMP file, not a 24 bit file.
Obviously that program does nto accept 8bit BMP's. IM probably compressed it too!

If you work it out make sure you update here for other. I also will copy it into the BMP section of IM Examples, File formats

No, that other program explicitly says that it accepts 8-bit BMP alpha files, but I just can't get it to work.

If I take an image in Photoshop, and go to Mode -> Adjustments -> Grayscale, and save it as 8-bit, it works though.

I just need to get the image to about 65kb...

And when I perform the -colors 256 operation on a 192kb BMP (I think 24-bit TrueColor or something), it gives me an image that's only 3 kb, when I need 65 kb.

I don't know if this will help, but I'm using 256x256 sized images.

Thanks.

Could somebody please help?

If it's not possible to do it with ImageMagick, could somebody recommend a free command-line program that would do it?