Sunday, 1 October 2017

What is the difference between Monochrome, grayscale and 8-32 bit color images?

I am sure there are many of us who must have heard words like Monochrome, Black & White, Grayscale and 32 bit color images. These words carry more meaning when you have to deal with images being a dslr lover or photographer. I was trying to scan an image recently, and noticed the quality difference when I selected grayscale instead of black&white. It served as the source of motivation for this post. Let's dive in and see what's the difference in all these terminologies.
Monochrome photos: Monochrome image is known as binary image. Each pixel is stored as a single bit (0 or 1). A 640 x 480 monochrome image requires 37.5 KB of storage. It can also contain varying tones of only one color.
Black & White photos:
It has no Gray. It can also be considered as a special case of monochrome images. A good example of black & white would be chess board. All black & white printings are monochrome but not all monochrome printings are black and white. 

Grayscale photos:
Grayscale image has values varying from black to white. In other words, it has varying shades of gray. In simple words, a grayscale image has more details than a black&white image. A 640 x 480 sized grayscale image would require over 300 KB of storage.

Color images or photos: Can be either 8 bit, 24 bit or 32 bit.
8 bit: One byte for each pixel. Supports only 256 out of the millions color possible.(Calculated as 2^8)
24 bit: Each pixel is represented by 3 bytes as 1 byte=8 bits. These bytes are known as red, blue and green. 24 bit color images offer the largest possible color combinations. 256x256x256. (Calculated as 2^8 multiplied by 2^8 multiplied by 2^8).
32 bit: These images have 8 additional bits for alpha (transparency).
Tip for photoshop: Any RGB image that has 8 bits/channel is known as 24 bit image. 8 Bit for each red, blue and green color. Photoshop lists the bit depth as bits/channel. Sometimes organizations will ask for a 24 bit JPEG which means 24 bits in total or 8 bits/channel in the language of photoshop.

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