When describing grayscale algorithms, I’m going to focus on step 2 - using math to turn color values into a grayscale value. Replace the original red, green, and blue values with the new gray value.Use fancy math to turn those numbers into a single gray value.Get the red, green, and blue values of a pixel.How all grayscale algorithms fundamentally workĪll grayscale algorithms use the same basic three-step process: Different color models have different channels (sometimes the channels are colors, sometimes they are other values like lightness or saturation), but this article will primarily focus on RGB channels. Layering these channels on top of each other creates a full-color image. Most digital images are comprised of three separate color channels: a red channel, a green channel, and a blue channel. I will also refer frequently to color channels. This article will primarily reference the RGB and HSL color spaces. The RGB color space is represented as a cube, HSL can be a cylinder, cone, or bicone, YIQ and YPbPr have more abstract shapes. Different ways of representing color lead to different color spaces. A color space is a way to visualize a shape or object that represents all available colors. Several other technical terms will be used throughout my explanations. It tends to abstract the subject, allowing the photographer to focus on form and interpretation instead of simply reproducing reality.īecause the terminology black-and-white is imprecise - black-and-white photography actually consists of many shades of gray - this article will refer to such images as grayscale. Monochromatic photography is sometimes considered the “sculpture” variety of photographic art. If anything, the digital revolution has actually increased the popularity of monochromatic photography because any digital camera is capable of taking black-and-white photographs (whereas analog cameras required the use of special monochromatic film). Despite the eventual introduction of color photography, monochromatic photography remains popular.
So without further ado, here are seven unique ways to convert a full-color image to grayscale.īlack and white (or monochrome) photography dates back to the mid-19th century. To my knowledge, this is the only project on the Internet that presents seven unique grayscale conversion algorithms, and at least two of the algorithms - custom # of grayscale shades with and without dithering - were written from scratch for this very article. So rather than add one more “here’s a grayscale algorithm” article, I have spent the past week collecting every known grayscale conversion routine. I don’t like adding projects to this site that offer nothing novel or interesting, and there are already hundreds of downloads - in every programming language - that demonstrate standard color-to-grayscale conversions. I’m glad to finally have a place to send those queries!ĭespite many requests for a grayscale demonstration, I have held off coding anything until I could really present something unique. I have uploaded a great many image processing demonstrations over the years, but today’s project - grayscale conversion techniques - is actually the image processing technique that generates the most email queries for me.