How do RGB values from 0 to 1 get converted to a number from 0 to 255?

Is the RGB value simply scaled to a number from 0 to 255 to determine the colour of a pixel on the screen?

Answer 1

[Image Analyst]

RGB images have 3 color channels (planes). The values in each plane can be in the range of 0-255 if you want to display them.

[Anna]

I thought that they had to be in the range 0 to 1, at least in colormaps in MATLAB the RGB values are always 0 to 1. I want to know whether for example the color [0.5 0.5 0.5] is outputted to the screen as [128 128 128], or whether the mapping is non-linear. The actual color of the pixel must eventually be determined by three 8 bit numbers (i.e. 0 to 255) - or does it depend on the monitor?

[Adam]

It is a simple linear mapping. I don't know off-hand whether [0.5 0.5 0.5] maps to [128 128 128] or [127 127 127], but the scaling is definitely linear.

[Image Analyst]

The color of the pixel is 3 numbers for R, G, and B. If you're displaying them on the screen, they must be uint8 which means they'll be in the range 0-255. Of course you can work with any range you want (0-1 or -999 to +12345 or whatever) or even floating point values internal to your program - nothing wrong with that. But to display you'll need to scale into the range 0-255 and cast to uint8.

Answer 2

[Tabitha]

check out

http://www.rapidtables.com/web/color/RGB_Color.htm