Glossaire des formats d'image

PNG (Portable Network Graphics)

A lossless raster image format with alpha transparency support. Ideal for logos, icons, screenshots, and any graphic where crispness matters more than file size.

Outils associés: PNG to JPG Converter, JPG to PNG Converter, SVG to PNG Converter

JPG / JPEG

A lossy raster format that compresses photographs aggressively using DCT. Ubiquitous compatibility — every OS and app reads it. No transparency support.

Outils associés: PNG to JPG Converter, HEIC to JPG Converter, Image Compressor

WebP

A Google-developed format offering both lossless and lossy modes plus animation and transparency. Typically ~25–30% smaller than JPG at similar quality; supported in every modern browser.

Outils associés: WebP Converter, Image Compressor

AVIF (AV1 Image File Format)

A modern image format derived from the AV1 video codec. Delivers ~50% smaller files than JPG at the same quality. Supported in all current Chrome, Edge, Firefox, and Safari.

Outils associés: AVIF Converter, AVIF to JPG Converter

HEIC / HEIF

Apple's default photo format on iPhone since iOS 11. Uses HEVC compression to halve the file size of an equivalent JPG. Limited support on Windows and Android without plugins.

Outils associés: HEIC to JPG Converter

EXIF (Exchangeable Image File Format)

Metadata embedded in images by cameras and phones — camera model, lens, timestamps, and GPS coordinates. Strip it before sharing publicly to avoid leaking location.

Outils associés: EXIF / Metadata Remover

Alpha channel

The fourth color channel (alongside R, G, B) that encodes per-pixel transparency. PNG, WebP, and AVIF carry it; JPG does not.

Outils associés: JPG to PNG Converter, AI Background Remover, SVG to PNG Converter

DPI / PPI

DPI (dots per inch) describes printer output density; PPI (pixels per inch) describes on-screen display density. Web images are sized in pixels — DPI only matters for print.

Outils associés: Image Resizer

Lossy vs. lossless compression

Lossy compression discards image information to save size (JPG, AVIF, WebP lossy). Lossless compression shrinks files without quality loss (PNG, WebP lossless).

Outils associés: Image Compressor, WebP Converter

Chroma subsampling

A JPG/AVIF compression trick that stores color (chroma) at lower resolution than brightness (luma), exploiting the eye's lower color sensitivity. '4:2:0' halves chroma resolution in both axes.

Outils associés: Image Compressor, WebP Converter, AVIF Converter

ICC profile

A color profile that tells a viewer exactly which colors the image's pixel values represent. Critical for print work and wide-gamut displays.

Outils associés: EXIF / Metadata Remover

Progressive JPEG

A JPG variant that renders low-resolution first, then refines — so users see something before the whole file loads. Slightly larger than baseline JPG but better perceived performance.

Outils associés: Image Compressor

Animated GIF vs. APNG

GIF caps at 256 colors per frame and is ancient; APNG extends PNG with frames and full-color alpha but is larger. For rich motion, WebP or WebM often outperform both.

Outils associés: GIF Maker

SVG (Scalable Vector Graphics)

An XML-based vector format. Scales to any size without pixelation, making it ideal for logos, icons, and illustrations.

Outils associés: SVG to PNG Converter

ICO

A Microsoft container that packs multiple raster sizes (16–256 px) of the same image into one file. Used for favicon.ico and Windows app icons.

Outils associés: ICO / Favicon Maker

QR code

A two-dimensional barcode that encodes text, URLs, or small payloads. Standardized by Denso Wave in 1994 and now the default offline-to-digital bridge.

Outils associés: QR Code Generator

QR error correction (L/M/Q/H)

QR codes include Reed–Solomon parity so they remain scannable when partially damaged. L tolerates ~7% loss; H tolerates ~30% but stores less data.

Outils associés: QR Code Generator

Aspect ratio

The proportional relationship between an image's width and height. Common values: 1:1 (square), 4:3 (classic), 16:9 (widescreen), 9:16 (vertical video).

Outils associés: Image Cropper, Image Resizer

Bit depth

The number of bits per color channel — 8-bit gives 256 levels and 16.7 M colors; 10- or 12-bit enables HDR and reduces banding in gradients.

Outils associés: Image Compressor

Favicon

The small square icon associated with a website — appears in browser tabs, bookmarks, and history. Typically served as favicon.ico, SVG, or a set of PNGs.

Outils associés: ICO / Favicon Maker