À propos des fichiers JPG

JPG (JPEG Image · Format d'image)

Lancement 1992 Par Joint Photographic Experts Group

JPEG Image (.jpg) est un format de fichier pris en charge par KaijuConverter pour l’archivage, l’échange professionnel et la conversion multiplateforme.

Famille

Raster & Vector Images

Extension

.jpg

Type MIME

image/jpeg

Utilisable comme

Entrée Sortie

L'histoire

COMMENT JPG
A VU LE JOUR.

1992

1996

JPEG was defined in 1992 by the Joint Photographic Experts Group — a committee of researchers from ISO, IEC, and ITU that spent five years solving a problem the rest of computing had ignored: how to make photographs small enough to transmit over a 9600-baud modem. Their answer was a clever lossy compression scheme that exploits how the human eye perceives color and detail: the algorithm discards information the eye can't easily see, keeping what matters.

JPEG's dominance was cemented by early digital cameras and the commercial web. By 1996 every camera manufacturer shipped JPEG as the native save format, and every browser rendered it natively. Thirty years on, roughly one out of every three files on the internet is a JPEG.

CURIOSITÉS ET
ANECDOTES.

The name is always JPEG — the committee — but the usual file extension is .jpg because MS-DOS only supported 3-letter extensions.

JPEG compression uses the Discrete Cosine Transform — the same math as MP3 audio compression.

You cannot truly edit a JPEG: every save re-compresses and degrades the image. This is called "generation loss".

A 1-megapixel JPEG at quality 80 is about 250 KB. The same image as uncompressed BMP is 3 MB.

Progressive JPEG was invented so images would load top-to-bottom in a low-res preview first — still useful today.

POINTS FORTS ET
LIMITES.

Points forts

Excellent compression ratio for photographs (10:1 or better without visible quality loss).
Universal support — every camera, phone, OS, and browser reads JPEG natively.
Adjustable quality setting balances file size against visual fidelity.
Embeds EXIF metadata (camera model, GPS, exposure) automatically.
Progressive rendering for graceful loading over slow networks.

Limites

Lossy — every save degrades the image further (generation loss).
No transparency channel (use PNG or WebP for that).
Visible compression artifacts on text, sharp edges, and flat colors.
Limited to 8 bits per channel — poor for HDR or print work.
Baseline JPEG tops out at 65,535 × 65,535 pixels.

Tailles et poids typiques

Phone photo (12 MP, quality 85)

2–5 MB

Web thumbnail (400px)

20–60 KB

Full-page magazine photo

500 KB – 2 MB

Social-media square (1080×1080)

100–400 KB

Spécifications techniques

MIME type: image/jpeg
Compression: Lossy — Discrete Cosine Transform + quantization + Huffman coding
Color depth: 8 bits per channel (24-bit RGB or 8-bit grayscale)
Max dimensions: 65,535 × 65,535 pixels (baseline)
Transparency: Not supported
Typical quality: 75–90 for web, 95+ for print

CONVERTIR DEPUIS
JPG

jpg jpg jpg png jpg webp jpg avif jpg gif jpg bmp jpg tiff jpg ico jpg svg jpg psd jpg eps jpg pdf jpg tga jpg exr jpg pcx jpg sgi jpg dpx jpg pnm jpg xbm jpg xpm jpg wbmp jpg miff jpg ai

CONVERTIR EN
JPG

png jpg webp jpg heic jpg svg jpg bmp jpg tiff jpg gif jpg avif jpg pdf jpg ico jpg psd jpg dng jpg eps jpg heif jpg cr2 jpg nef jpg arw jpg orf jpg rw2 jpg tga jpg exr jpg hdr jpg xcf jpg jp2 jpg jxl jpg pptx jpg cr3 jpg raf jpg sr2 jpg pef jpg icns jpg svgz jpg jpeg jpg jfif jpg pgm jpg ppm jpg pbm jpg emf jpg wmf jpg dds jpg pcx jpg sgi jpg dpx jpg pnm jpg xbm jpg xpm jpg fits jpg wbmp jpg cin jpg miff jpg raw jpg ai jpg doc jpg docx jpg odt jpg rtf jpg xls jpg xlsx jpg ods jpg ppt jpg odp jpg csv jpg tsv jpg indd jpg cdr jpg mp4 jpg mov jpg mkv jpg avi jpg webm jpg flv jpg wmv jpg mpeg jpg 3gp jpg ogv jpg vob jpg m4v jpg ts jpg m2ts jpg mts jpg swf jpg mpg jpg asf jpg dv jpg f4v jpg h264 jpg h265 jpg m2v jpg mjpeg jpg mxf jpg rm jpg rmvb jpg divx jpg nut jpg y4m jpg jpg jpg dcm jpg

Cas d'usage courants

Web photos, digital photography, email attachments, social media images.