1. The image
Sample image
Image: 256 × 256
0.066 megapixels
Grid: 16 × 16
CV Lab – 1
Computer Vision Lab: Pixels as Numbers
Explore how a grayscale image can be stored as a 2D grid of numbers. Change brightness, contrast, resolution and zoom, then compare the picture with its pixel values.
1 pixel = 1 byte
In this grayscale example, each pixel stores one 8-bit value.
0 to 255
0 = black, 255 = white, and values in between = shades of gray.
8 bits = 256 values
Eight binary digits can represent 2⁸ = 256 different values (0 through 255).
Shift pixel values darker or lighter.
Separate dark and light values.
More cells show more image detail.
Enlarge or shrink the pixel picture.
2. The bitmap of numbers
Each cell = 1 pixel value
Hover over a cell to inspect it.
Pixel: —
Dark cells have low values; light cells have high values.
The grid shows the same adjusted grayscale data used to draw the image.
What should you notice?
Pixel value: Each cell stores a number from 0 to 255. A value of 0 appears black; 255 appears white.
Grayscale: One number per pixel is enough because the pixel represents only brightness, not a colour.
Image dimensions: An image with width × height pixels has that many pixels. For an uncompressed 8-bit grayscale image, the pixel data uses approximately width × height bytes, excluding file headers and other metadata.
Resolution vs zoom: Resolution changes how many pixel samples are used. Zoom only changes how large the image appears on screen.
Try this: Move brightness to −60, then +60.
Set contrast to 40%, then 160%. Reduce grid resolution to 8 × 8
and increase it to 32 × 32. What happens to the values and the
visible detail?