Tools to convert from 16-bit RGB to 24-bit RGB and vice versa


Are there any image editing or research tools, commercial or otherwise which will allow me to:

  • map colors (images) from 16-bit RGB (565) space to 24-bit RGB (888) space or vice versa
  • save files in PNG, GIF, or JPEG
  • give user the ability to control how colors are mapped from 16-bit space to 24-bit space.

Here's a little background for this request.

I'm working on a project evaluating an LCD display panel. The native bit depth of the panel is 24-bits (RGB 888) and it is currently available on an evaluation kit that uses an LCD controller that supports 24-bit output only.

The LCD controller on the product for which this panel is being evaluated only supports 16-bit output (RGB 565). In the final design the remaining bits for each color channel on the panel will be connected in some way.

The evaluation kit does not take RGB inputs (as mentioned above it only takes PNG, JPEG, or GIF). I'm looking for a way to create 16-bit and 24-bit RGB files which will then be converted to a PNG. By manipulating the values of the R, G and B channels in the source files (16-bit and 24-bit) I want to compare the difference between driving a 24-bit display with 24-bits of color and 16-bits of color (extended to 24-bits).

I'd also be interested in learning about others experiences with this sort of evaluation and the sanity of my proposed test methodology.


11/12/2012 9:19:00 AM

Accepted Answer

I don't think you'll be able to accurately mimic the 16bit display without knowing more about the dithering method it uses. Some 16bit and 18bit displays animate their dither pattern, meaning they actually look better than you may expect (I believe lots of laptop displays use 18bit with an animated dither).

Also, there's quite a few dithering methods (patterned, stochastic etc), with a big range of results.

Photoshop's indexed colour mode converts to index colour (of course!), but it tops out at 256 colours, so it doesn't do what you're after.

If you save an image as a BMP from Photoshop, you are given the option to save as 16bit with the R5 G6 B5 mode (click Advanced Modes when saving). If you want to convert that image back to 24bit, simply open it again in Photoshop. The image won't gain any quality back, but I assume that's what you're after.

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11/12/2012 11:45:00 AM