Image format glossary
The concepts behind every conversion — compression, transparency, metadata, and resolution — defined in plain English, each linked to the tool that puts it to work.
- Image Compression→Image compression reduces an image file's size by removing redundant or imperceptible data. Two methods exist: lossy compression discards detail for much smaller files, and lossless compression shrinks files with no quality loss.
- Lossy vs Lossless Compression→Lossy compression discards image data to shrink files, causing slight quality loss; lossless compression reduces file size with no quality loss by encoding data more efficiently. JPG is lossy; PNG is lossless.
- Alpha Transparency→Alpha transparency is a channel that stores how opaque each pixel is, letting parts of an image be fully or partly see-through. PNG, WebP, AVIF, and GIF support it; JPG does not.
- EXIF Metadata→EXIF metadata is information a camera embeds inside a photo — date, time, GPS location, camera model, and exposure settings. It travels within the file and can reveal private details when images are shared.
- DPI vs PPI→PPI (pixels per inch) measures image density on a screen; DPI (dots per inch) measures ink dots a printer lays down. Both describe resolution, but PPI applies to digital displays and DPI to physical printing.
- Color Depth→Color depth is the number of bits used to store each pixel's color. 8-bit holds 256 shades per channel — about 16.7 million colors total; higher depths store more shades, reducing visible banding in gradients.
- Chroma Subsampling→Chroma subsampling shrinks files by storing color at lower resolution than brightness, exploiting the eye's weaker sensitivity to color detail. JPG and WebP use it, written as 4:4:4, 4:2:2, or 4:2:0.