Raster Image

A raster image represents a picture as a grid of pixels, each carrying color information. Also called bitmap images, common formats include PNG, JPEG, GIF, BMP, and WebP. Raster images excel at complex color reproduction like photographs, and formats such as PNG and JPEG can be displayed on a wide range of devices and software.

PNG is the usual raster format for QR code export. Its lossless compression preserves the sharp black-white module boundaries that JPEG's lossy compression would blur. JPEG introduces compression artifacts at module edges that can reduce scan accuracy, making it unsuitable for QR codes.

The main weakness of raster images is quality degradation when scaled up. Enlarging beyond the original resolution stretches pixels, creating jagged edges (aliasing) and blur. A QR code generated for a business card will fail to scan if enlarged to poster size. To avoid this, either generate at sufficient resolution for the intended use (work back from the print size and print resolution to the pixel count you need), or use SVG (vector format). SVG stores shapes as coordinates and path descriptions (lines and curves) that are redrawn at the displayed size, so it does not degrade when scaled. In practice, use SVG for web display; for print, follow the printer's file requirements, preferring a vector format (SVG or PDF) and falling back to a PNG at sufficient resolution only where vector files are not accepted.