Bitmap

A bitmap (raster image) is a digital image stored as a rectangular grid of pixels, each carrying color information. Its quality is defined by resolution — the pixel count horizontally and vertically — and bit depth, the number of colors each pixel can represent. Bitmaps are the most common way of storing images: every digital photograph, screenshot and scan is a raster.

How a bitmap works

File size grows with pixel count and color depth, so bitmaps are almost always compressed. Lossy compression (JPEG, and most uses of WebP and AVIF) discards detail the eye barely notices, achieving dramatically smaller files; lossless compression (PNG, GIF) preserves every pixel at the cost of size. The key limitation of rasters shows up when scaling: enlarging requires interpolation and produces blur or visible pixelation, whereas vector graphics, described by mathematical curves, scale without any loss. PNG, WebP and AVIF additionally support an alpha channel — true transparency, useful for overlays and product cutouts.

Practical applications

Bitmaps are the right choice wherever continuous tones appear: product photography, article images, textures, documentation screenshots. On the web their optimization matters enormously — converting to modern formats such as WebP or AVIF can cut image weight by tens of percent, while responsive images (the srcset attribute) and lazy loading reduce transfer on mobile devices. This feeds directly into Core Web Vitals, especially the LCP metric, and therefore into search rankings. For print work the rules differ: a minimum of 300 DPI at the target physical size is the standard, and color is prepared in CMYK rather than RGB.