How is a sepia tone created?

Question

What are the basic operations needed to create a sepia tone? My reference point is the perl imagemagick library, so I can easily use any basic operation. I've tried to quantize (making it grayscale), colorize, and then enhance the image but it's still a bit blurry.

Answer 1

Sample code of a sepia converter in C# is available in my answer here: What is wrong with this sepia tone conversion algorithm?

The algorithm comes from this page, each input pixel color is transformed in the following way:

outputRed = (inputRed * .393) + (inputGreen *.769) + (inputBlue * .189)
outputGreen = (inputRed * .349) + (inputGreen *.686) + (inputBlue * .168)
outputBlue = (inputRed * .272) + (inputGreen *.534) + (inputBlue * .131)

If any of these output values is greater than 255, you simply set it to 255. These specific values are the values for sepia tone that are recommended by Microsoft.