8-bit vs 16-bit Precision, and Indexing

[Mango Turtl]

(08-22-2021, 08:01 AM)rich2005 Wrote: 8 bit and 16 bit for RGB images are the number of bits per channel so 8 bit = 24 bits per pixel , 16 bit = 48 bits per channel/

That determines the number of colours available. Covert from 16 bit to 8 bit and colours are lost but it all depends on the image, it might not be as severe as it sounds. 

Indexed Images are very different,  each pixel is assigned a colour from a colormap, the colour map only contains 256 values so you only get what is available in the color map. Converting from RGB to Indexed will try and make the best colormap from the image. and can 'dither' the boundary between colours to give an impression of a smooth transition.

see: https://www.cambridgeincolour.com/tutori...-depth.htm which is worth a read.

8 bit = greyscale
24 bit = 16 million colours
48 bit = 281 trillion colours

Quote:Edit: Looking at the colorcube analysis, both the original 16-bit and converted 8-bit PNGs have the same amount of unique colors. Obviously, the indexed version only has 256. Does this mean that if I don't index, no actual visible information is lost by converting it to 8-bit?

As far as I know, colourcube is stuck in the past and is only 8 bit ( 24 bit 16 million colours)

Okay, I'm not that techy so I might need a rephrase. But what I'm getting is that unless there's MORE than the 16 million color limit in the original 16-bit image, then converting it into 8-bit won't change much. And don't worry, I'm definitely not messing with indexing. Just trying to lower file size without reducing resolution or detail by much.