Raster Image

Updated 22 Sep 2026

•
What it is
- •
  an image represented as a grid of pixel values
•
Representaion
- •
  grayscale - typically an $H\times W$ array
- •
  RGB - typically an $H\times W\times3$ array
- •
  RGB with alpha - typically an $H\times W \times 4$ array
•
Storage example
- •
  an uncompressed $640 \times 480$ image with three 8-bit channels contains $640 \cdot 480 \cdot 3 = 921{,}600$ bytes of pixel data before headers, padding, or metadata
•
Caution
- •
  compressed file size can differ greatly from the decoded array size
- •
  "bitmap" can refer generically to a raster representaiton; BMP is one specific file format
•
Distinguish from
- •
  Vector Graphics

Linked references 4