color reduction tool

by **StephC** » Jun 22, 2003 @ 4:17pm

Is there a *good* (and free) tool to reduce colors to 16 (565) and 12 bits ?

Please don't mention Photoshop or Paint Shop Pro...

by **DillRye** » Jun 22, 2003 @ 7:45pm

you could try "the gimp". Its a free open source alternative to photoshop/paint shop pro. Im pretty sure theres a version for windows.

by **sponge** » Jun 22, 2003 @ 8:40pm

The Gimp has a windows port, GTK is included. Other than that, PSP is the best solution, you might just have to shell out for it.

by **Sm!rk** » Jun 22, 2003 @ 9:02pm

I use Debabelizer for all my image conversion, its a commercial product however ($450).

by **Digby** » Jun 23, 2003 @ 1:18am

Why would you want to convert an image to 12 bits?

by **StephC** » Jun 23, 2003 @ 11:23am

Digby wrote:Why would you want to convert an image to 12 bits?

Old devices (ipaq 36xx and 37xx) have 12bits screens (4096 colors).

16 bits pictures are not perfectly rendered on 12 bits screens...

For now I'am trying to use ImageMagick, it's color reduction algorithm seems to be very efficient and versatile.

by **Dan East** » Jun 23, 2003 @ 1:30pm

It's a shame to compromise the quality for all devices, just for a limitation found on only 10% of the devices. 12 bit really looks bad compared to 16 bit in most cases.

Dan East

by **Guest** » Jun 23, 2003 @ 2:01pm

Dan East wrote:It's a shame to compromise the quality for all devices, just for a limitation found on only 10% of the devices. 12 bit really looks bad compared to 16 bit in most cases.

Dan East

I do not want to compromise the quality for all devices, I want to release 16 bits AND 12 bits versions.

by **Digby** » Jun 23, 2003 @ 4:29pm

The 12 bit devices have 16 bit frame buffers, or am I missing something?

by **StephC** » Jun 23, 2003 @ 8:27pm

Digby wrote:The 12 bit devices have 16 bit frame buffers, or am I missing something?

12 bits devices HAVE 16 bits frame buffer, but they can't display all the 65536 colors... only 4096 of them.

by **Dan East** » Jun 23, 2003 @ 8:38pm

Yes, so it uses the closest color. The 16 bit to 12 bit conversion is done at the hardware level. Are you wanting a converter that will dither the images to decrease banding? That is the only point I can see in pre-processing the images to 12 bit. Even so, I would prefer to do the dithering at load-time for the devices that need it (assuming I could find such an algorithm).

Dan East

by **Kzinti** » Jun 23, 2003 @ 10:31pm

Dan East wrote:Even so, I would prefer to do the dithering at load-time for the devices that need it (assuming I could find such an algorithm).

I would also like to do that. But how does one detect such devices? The only way I know is to explicitely detect the iPAQ 36xx devices. Are there any others with 12 bits display?

by **Dave H** » Jun 24, 2003 @ 12:08pm

Thierry wrote:
Dan East wrote:Even so, I would prefer to do the dithering at load-time for the devices that need it (assuming I could find such an algorithm).

I would also like to do that. But how does one detect such devices? The only way I know is to explicitely detect the iPAQ 36xx devices. Are there any others with 12 bits display?

As a halfway compromise without going to too much effort, I just applied a bit of random noise to my 16-bit graphics. This looks alright on 12-bit devices (because it provides a bit of stipple) and 16-bit devices (the noise doesn't look too bad, just looks textured).

I'm too lazy to specifically target 12-bit and 16-bit, I'd rather spend my effort targetting 4-bit like Triums and 31xxs ;)

by **StephC** » Jul 16, 2003 @ 5:50am

So, I've made an implementation of ordered dithering for 16 and 12bits :

This may be useful to generate smooth gradients etc..

Enjoy :)

Code: Select all

1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 
32 
33 
34 
35 
36 
37 
38 
39 
40 
41 
42 
43 
Uint32 dither4[4][4] = { {0, 4, 1, 5}, {6, 2, 7, 3}, {1, 5, 0, 4}, {7, 3, 6, 2} };

PIXEL Dither16(Uint32 x, Uint32 y, Uint32 Red, Uint32 Green, Uint32 Blue)
{
  Uint32 dither;
  Uint32 pRed, pGreen, pBlue;

  dither = dither4[y&3][x&3];

  pRed   = Red  >>3;
  pGreen = Green>>2;
  pBlue  = Blue >>3;

  if((dither < Red&7)   && pRed   < 31) { pRed   = pRed++;    }
  if((dither < Green&3) && pGreen < 63) { pGreen = pGreen++;  }
  if((dither < Blue&7)  && pBlue  < 31) { pBlue  = pBlue++;   }

  return (pRed << 11) | (pGreen << 5) | (pBlue );

}

/////////////////////////////////////////////////////////////////////////////////

PIXEL Dither12(Uint32 x, Uint32 y, Uint32 Red, Uint32 Green, Uint32 Blue)
{
  Uint32 dither;
  Uint32 pRed, pGreen, pBlue;

  dithy = y & 0x3;
  dithx = x & 0x3;

  dither = 2*dither4[y&3][x&3];

  pRed   = Red  >>4;
  pGreen = Green>>4;
  pBlue  = Blue >>4;

  if((dither < Red&15)   && pRed   < 15) { pRed   = pRed++;    }
  if((dither < Green&15) && pGreen < 15) { pGreen = pGreen++;  }
  if((dither < Blue&15)  && pBlue  < 15) { pBlue  = pBlue++;   }

  return (pRed << 12) | (pGreen << 7) | (pBlue<<1 );
}
43 lines; 8 keywds; 48 nums; 220 ops; 0 strs; 1 coms    Syntactic Coloring v0.4 - Dan East

PS : isn't "code" section buggy ? (I use Opera)

by **Dan East** » Jul 16, 2003 @ 10:12am

Thanks for sharing your code.

StephC wrote:PS : isn't "code" section buggy ? (I use Opera)

No, it's been fixed (however there is a report of an issue with IE 5).

Dan East

color reduction tool

color reduction tool

Sort

Forum Description

Moderators:

Forum permissions