Image Glossary
Clear definitions of the image terms that actually matter — and a tool to put each one into practice.
Alpha Channel (Transparency)
An extra channel that records how transparent each pixel is.
Aspect Ratio
The proportional relationship between an image’s width and height (e.g. 16:9).
Compression Ratio
How much smaller a compressed file is versus the original.
DPI (Dots Per Inch)
A print-resolution measure: how many ink dots fit in one inch of paper.
EXIF Metadata
Hidden data stored in a photo — camera, date, settings and sometimes GPS.
Image Metadata
Information stored inside an image file beyond the pixels themselves.
Lossy vs Lossless Compression
Lossy trades some detail for much smaller files; lossless keeps every pixel.
Pixel
The smallest single point of color in a raster image.
PPI (Pixels Per Inch)
The pixel density of a screen or image — the digital counterpart of DPI.
Raster vs Vector
Raster images are grids of pixels; vector images are math-defined shapes.
sRGB Color Space
The standard color space for the web and most screens.
WEBP Format
A modern image format with smaller files and transparency support.