High quality DOOM palette conversion

[Maes]

Is there any known utility to make "high quality" conversions of 8-bit or truecolor images to the "one true 8-bit Doom palette" ? I know DMGRAPH and DEUTEX do this conversion internally but it only works for 8-bit BMPs, not truecolor, and it surely isn't "hi-quality" (dithering, anyone?).

So, is there any utility optimized for converting stuff to the doom palette, or a way to use a generic software to reduce colors using a specific palette?

And, assuming it is possible to create a "doom friendly" 8-bit image, how can it be imported into a PWAD without further color reductions/approximation?

Thanks in advance.

[myk]

Use your graphics editing application for that (Paint Shop, Photoshop, The GIMP, and so on), and their different dithering functions. Some work better for some sorts of pics, and others for other sorts. You might also try different dithering on different parts of a pic, and then merge the sections with cut and paste. You'll still have to do some manual fixing up, though.

[Graf Zahl]

Since Doom's palette is so limited there is no chance of 'hi-quality' conversions for many graphics. Regardless of dithering or whatever other means to account for the lack in colors most pictures not specifically designed for Doom's palette will look quite ugly. There's just too many important colors missing.

[Maes]

Hmm...exactly what I feared. I know I can obtain a high-quality 8-bit dithering e.g. from PSP, but the palette used WON'T be the DOOM one, and when I try importing it with WINTEX or DMGRAPH it will be ruined.

I followed an image processing course last year though...and one of the most "hot" assignments for course-end projects was reducing an image's colors to exactly the set of colors you desired (I chose something else but meh...).

If there IS enough request I guess someone could build such an utility with the following features:

• High quality conversion of any bit-depth to 8-bit and using ONLY the colors present in the DOOM palette
  
• Direct importing them into PWADS to avoid utilites like WINTEX that would downgrade the colors twice
  

Or , pretty please, if someone knows how to use a fixed palette with PSP or Photoshop...

[myk]

Maes said:
Or , pretty please, if someone knows how to use a fixed palette with PSP or Photoshop...

I know PSP lets you apply a 256 color palette in the PAL format (like the one that's in idgames), either retaining the indexes (generally useful when you are recoloring) or applying the new colors as well as possible (with different dithering options). At least v6.01 did. I can't walk you through the steps as I don't have it installed, but checking the help function and the menus should be enough.

[Maes]

Well, I figured I could share the steps needed to use PSP (9.x and above at least) to apply a high-quality any-bit-depth to Doom palette conversion.

First, make sure the doom.pal and heretic.pal files are in the paths configuration of PSP.

Open up your image without applying any color reductions, go to Image->Palette->Load Palette and select "Load palette" (the other options will be grayed out if you're working on images with bit depth > 8 bits).

Select "doom" (it should appear in the drop down box, if it's within a visible palette path) and then you can either select "nearest color" or "error diffusion" as a color reduction method, and also "keep indexes" if you were working on an 8-bit image already.

"Nearest color" gives very "flat" results and you shouldn't use it unless the result satisfies you. In general, the image will appear very posterized, so unless it works for you, it's generally very poor, and not much better than the way WinTex or DMGraph would do the "conversion". You just save one 24->8 bit conversion step.

"Error diffusion" tries to appear more accurate with dithering etc. but may result in excessive grainynessn (random colored pixels will appear to approximate the original hue). From a distance, especially high-resolution images may appear quite close to the original, but think about how ugly random colored pixels would appear in a lo-res texture or skybox...this method is recommended only for hi-res skyboxes with little stretching, hi-res textures, and generally for use only with very "clean" images that will yield very little "peppering".

"Keep indexes" is almost useless for converting random images, unless you are 100% sure of what you're doing or you just don't care.

Anyway, after you're done with that step and saved the image as an 8-bit BMP, import it as usual. With a little luck, your favourite WAD resource editor WON'T ruin the image twice trying to re-apply palette conversion.

Some extra experience tips to keep in mind while downconverting:

• If an image is to be seriously reduced in resolution (such as a photo) before use in the game, apply the resolution reduction first, then color reduction. This way, downscaling will be more accurate, and you won't downscale nasty chunks of approximate color. As a side effect, this will also make the job of the palette reducer easier, as there will be less pixels and less colors/details to work on
  
• Some colors just don't render well with DooM palette, especially shades of blue. If you really want to render a nice blue sky, consider hand-retouching it, as automatic color reduction will usually render light blue as grey.
  
• You can also apply some pre-processing to the image while still in truecolor mode (especially color balance, contrast, removing sharpness) in order to approach doom colors best, ease color reduction and lessen dithering artifacts.
  

Such is the path of a Doom texturer.

[deathbringer]

I always used to open the bitmap to be replaced in Wintex (into paint), using "paste from" to bring in the new image, and then closing the file, that generally gave me decent conversions though sometimes oranges and yellows (like the flames from the flamethrower tank in my Insanity Please wad) would turn green

[Bucket]

Maes said:

...

NEVER USE DITHERING NEVER EVER EVER NEVER ARRRRGH

[Maes]

Bucket said:

NEVER USE DITHERING NEVER EVER EVER NEVER ARRRRGH

I know it doesn't look pretty at typical DOOM resolutions, read my post carefully. It could only look kinda OK on 1024 x 256 skies or even larger ones, or if the FINAL RESULT doesn't appear terribly grainy.