16 bit to 8 bit
simple instructions will allow you to change your high color image to the 256 color format JJ2 uses. There are other ways, but this is the easy way.
First open up your 16bit (or higher) image and then save it as a copy (never work on the original image when you don't know what you're doing ;).
example: Open 'myset.bmp', and save it as 'myset2.bmp'
In 'myset2.bmp', in PSP, go "Colors -> Decrease Color Depth -> X Colors (4/8 bit)...", or press Ctrl+Shift+6
In the space provided in the window, type in the a number from around 176-159 (it may be higher or lower... test 'em out) - it depends on your tileset. Start in the higher range, but you may have to come back and lower it more. I prefer nearest color, because it's better ;). Make sure "Include Windows" colors is NOT selected. Also you may want to select "Reduce color bleeding", but I don't because, well I never used anything higher than 256 colors :]
Make sure your mask file is also in an acceptable file format (Bitmap is my favorite)... Now save them files.
Then build the tileset using the temporary image ("myset2.bmp") in JCS "WITH" selecting the remap palette option (YES!! BELIEVE OR NOT I WANT YOU TO HAVE THIS OPTION ON!!!). If it gives you an error saying it couldn't remap "xx colors" undo untill it's back in 16bit and then after Ctrl+Shift+F6 type in "the number you entered before" minus "the number JCS said it couldn't remap".
Once JCS compiles it without an error, run a level using this tileset (it doesn't have to be a whole level - just a background will do because it gets annoying with the blurring). Take a screenshot and open it up in PSP. If you only took one, it should be called Jazz0001.pcx (I think) in your JJ2 directory.
Then go "Colors -> Save Palette", and type in something to call it (ex: "C:\myset.pal"). It's best to have the type as "PAL - JASC Palette".
Then open your original image ("myset.bmp") and go "Colors -> Load Palette", Shift+O, and select the palette you just saved ("C:\myset.pal") and select "Nearest Color Matching" and hit Open. Then of course you save the image and rebuild the tileset using it.
This is the best palette you can get without doing a ton of work. Even with the ton of work, it doesn't turn out much better, and in a lot of cases - it turns out worse.
Added on: Saturday, June 2 7.05 am. Made by Ice M A N.