Representing Images Using Pixels and Colour Depth

Introduction

Digital images are made up of tiny squares called pixels. Each pixel represents a single point of colour in the image. The number of pixels an image contains determines its resolution, and the way each pixel's colour is represented determines its colour depth.

Pixels

A pixel is the smallest unit of information in a digital image. It is a single point of colour, and when millions of these points are arranged together, they create the image we see.

Colour Depth

Colour depth refers to the number of bits used to represent the colour of a single pixel. The higher the colour depth, the more colours can be displayed.

Here's a breakdown of common colour depths:

• 1-bit: This represents two colours, typically black and white.
• 8-bit: This allows for 256 colours (28), commonly used in grayscale images.
• 24-bit: This allows for 16.7 million colours (224), a standard colour depth for most digital images. Each colour component (red, green, blue) uses 8 bits, resulting in 256 shades per component.
• 32-bit: This allows for the same number of colours as 24-bit, but uses an additional 8 bits for transparency.

Representing Colour

The most common way to represent colour in digital images is using the RGB colour model. RGB stands for red, green, and blue, the three primary colours of light. Each pixel is represented by three values, one for each primary colour. These values are usually represented as integers between 0 and 255, where 0 represents the absence of the colour and 255 represents the maximum intensity of the colour.

For example, the colour red is represented by (255, 0, 0), green by (0, 255, 0), and blue by (0, 0, 255). White is represented by (255, 255, 255), and black by (0, 0, 0).

Example

Let's consider a simple image of a red square on a white background.

     +---+---+
     |   |   |
     +---+---+
     | R |   |
     +---+---+
     |   |   |
     +---+---+

Each pixel in this image can be represented by an RGB value:

• White pixels: (255, 255, 255)
• Red pixels: (255, 0, 0)

By combining these pixel values, we can reconstruct the entire image.

Conclusion

Understanding the concept of pixels and colour depth is crucial for comprehending how digital images are stored and processed. By representing images as a collection of individual pixels, we can manipulate and analyze them in various ways, from editing software to image recognition algorithms.