Plugin/Filter to limit colours to more than 256? or to 18bit

[lemony]

I would like to make an image fit to a specific number of colours well above the 256 limit of a GIF. Or perhaps just to make it into an 18-bit one (262,144 colours).


Thanks

[xnview]

I would like to make an image fit to a specific number of colours well above the 256 limit of a GIF. Or perhaps just to make it into an 18-bit one (262,144 colours).

Sorry it's not possible to make a colormap picture with more than 256colors

[lemony]

Thanks,

To clarify, I didn't mean a GIF specifically. I would save it as a JPG, PNG or BMP..etc.

The saving format isn't my concern..it is more the ability to reduce the colors of an image (preferably to a set of "equaly spaced"/"balanced" predefined colours in a spectrum so that the image wuld get dithered to those).

So i guess it is a filtering really, not a format.

[foxyshadis]

Something like posterize? In xnview it's in image->map. It's a per-channel color reduction, but it's very coarse and unconfigurable. No dithering at all, no adaptive palettes. 18-bit is 6-bits per channel, which is labeled 64 in xnview.

Otherwise there are probably photoshop plugins in that vein out there, I haven't run into them but I've never needed one.

[XnTriq]

• Telegraphics – digital technology for the visual arts
  • Free plugins for Photoshop & Illustrator and other software
    • 12bits Filter
      Reduces colour depth of each channel of an image to 4 bits/16 values (4096 colours). Useful for cell phones and mobile devices.
    • 5_6_5 Filter
      Reduces colour depth of channels to 5 bits red, 6 bits green, 5 bits blue (total 16 bits or 65536 colours). Applies error diffusion dither. Useful for some mobile devices. Also includes 5/5/5 variation (32768 colours).
• Graphest: DepthDither
  Graphest DepthDither is a free filter plug-in for Photoshop, it mainly concerns on generating color dither in Photoshop. When you wants to use the image on LCD screen, such as mobile phone, the color depth is not 24 bit, and mostly it's 16 bit. If the image fills with gradient colors, the screen will display color steps, not continuous color. If you use the DepthDither to process the image, the result on PC and on mobile phone will be the same. DepthDither uses 3 ways to make the image seems to be continuous when the color is below 24 bit. It's just like Photoshop, provides diffusion, pattern and noise as the dither modes. You can choose the destination color depth, such as 2 bit, 4 bit, 12 bit, 15 bit, 16 bit, 18 bit, this is the main difference from Photoshop, the latter only provides less than 256 colors mode.

All of these filters are freeware.
DepthDither does not work with XnView (nor Fireworks v4, nor Paint Shop Pro v9, nor Photo-Paint v11, nor Picture Publisher v9, nor I****View v4, ...).

[XnTriq]

Ximage Quantizer is a photoshop plugin for image color quantization (color reduction) & dithering.

• Provides 10 color quantization methods.
• Provides 11 dithering methods.
• Calculates RMSE of the transformation.
• Allow choice of colorspace RGB or YCbCr
• Can be also used in other compatible plugin hosts (The Gimp, Irfanview, Xnview, Photo paint ....)
• Allow you to apply the algorithm to the selected portion of the image and not only to the full image.