apply a color value depending on decimal value imported

Question

To start with, I'm very new to C#!

I have a file with approximately 3 million lines. Each line contains a number between 0 and 1 (6 decimal places).

What I want to do is create a RGB value for each number depending where between 0 and 1 that number lies. For example, 0 would be green, 1 would be red, and all the numbers between would have a RGB value between green and red, created to represent how far down the color scale it is.

How do I calculate that RGB value?

Answer 1

Well, the simplest approach would be:

int red = (int)(Num * 255);
int green = (int)((1 - Num) * 255);
int blue = 0;

This way you get a gradient between red and green with green at 0 and red at 1.

However it sounds like you want to produce a visual scale for values that range from "good" to "bad". In that people often also want to place yellow in the middle to denote "okayish" values. Here's the code for that:

int red, green, blue;
if ( Num < 0.5 )
{
    red = (int)(Num * 2 * 255);
    green = 255;
    blue = 0;
}
else
{
    red = 255;
    green = (int)((2 - 2 * Num) * 255);
    blue = 0;
}

Answer 2

You'll need to derive an algorithm to convert your decimal value to three separate values, Red, Green, and Blue. Then use the built-in Color type to create your color with those values ( https://msdn.microsoft.com/en-us/library/cce5h557(v=vs.110).aspx ).

What you do with the colors from there is up to you.