Computer Science – 1.2 Multimedia | e-Consult

Increasing the bit depth of a bitmap image directly impacts the number of possible colours that can be represented for each pixel. The bit depth determines the number of bits used to store the colour information per pixel. For example, an 8-bit image can represent 2⁸ = 256 colours, while a 24-bit image can represent 2²⁴ = 16,777,216 colours.

Image Quality: Higher bit depth leads to improved image quality. With more colours available, smoother gradients and finer details can be represented. This reduces the likelihood of colour banding (visible steps in colour transitions) and posterization (loss of colour detail). The image appears more realistic and less 'pixelated', especially when viewed at different zoom levels.

File Size: The relationship between bit depth and file size is generally linear. Increasing the bit depth increases the amount of data required to store the image. A 24-bit image requires four times the amount of data as an 8-bit image (since each pixel has four bytes). Therefore, higher bit depth results in a larger file size. This can be a significant consideration for storage space and bandwidth when dealing with large numbers of images.

Trade-offs: The choice of bit depth involves a trade-off between image quality and file size. Higher bit depth provides better quality but increases file size. Lower bit depth reduces file size but can compromise image quality. The optimal bit depth depends on the intended use of the image. For example, a photograph intended for printing would benefit from a higher bit depth than an image used for a website where file size is a priority.