C# – Conditional formatting — percentage to color conversion

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What's the easiest way to convert a percentage to a color ranging from Green (100%) to Red (0%), with Yellow for 50%?

I'm using plain 32bit RGB – so each component is an integer between 0 and 255. I'm doing this in C#, but I guess for a problem like this the language doesn't really matter that much.

Based on Marius and Andy's answers I'm using the following solution:

double red = (percent < 50) ? 255 : 256 - (percent - 50) * 5.12;
double green = (percent > 50) ? 255 : percent * 5.12;
var color = Color.FromArgb(255, (byte)red, (byte)green, 0);

Works perfectly – Only adjustment I had to make from Marius solution was to use 256, as (255 – (percent – 50) * 5.12 yield -1 when 100%, resulting in Yellow for some reason in Silverlight (-1, 255, 0) -> Yellow …

Best Answer

I made this function in JavaScript. It returns the color is a css string. It takes the percentage as a variable, with a range from 0 to 100. The algorithm could be made in any language:

function setColor(p){
    var red = p<50 ? 255 : Math.round(256 - (p-50)*5.12);
    var green = p>50 ? 255 : Math.round((p)*5.12);
    return "rgb(" + red + "," + green + ",0)";
}
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