JPG File Interchange Format .JFIF, .JPG, .JPEG File Description

JPG File Interchange Format .JFIF, .JPG, .JPEG File Description

Grapher imports and exports JPEG JFIF raster image files.

The JPEG File Interchange Format, .JFIF, is an image file format standard. It is a format for exchanging JPEG encoded files compliant with the JPEG Interchange Format .JIF standard. It solves some of JIF's limitations in regard to simple JPEG encoded file interchange. As with all JIF compliant files, image data in JFIF files is compressed using the techniques in the JPEG standard, hence JFIF is sometimes referred to as "JPEG/JFIF".

JFIF defines a number of details that are left unspecified by the JPEG standard (ISO/IEC IS 10918-1, ITU-T Recommendation T.81):

Resolution and aspect ratio

The JPEG standard does not include any method of coding the resolution or aspect ratio of an image. JFIF provides resolution or aspect ratio information using an application segment extension to JPEG. It uses Application Segment #0, with a segment header of 'JFIF\x00', and specifies that this must be the first segment in the file, hence making it simple to recognise a JFIF file. Exif images recorded by digital cameras generally do not include this segment, but typically comply in all other respects with the JFIF standard.

Color Space

JPEG does not define which color encoding is to be used for images. JFIF defines the color model to be used: either Y for greyscale, or YCbCr as defined by CCIR 601. Since this is not an absolute color space — unless an ICC profile, colorspace metadata, or an sRGB tag is provided and interpreted – a decoded JFIF image will be in a device-dependent RGB colorspace. Hence, JFIF does not by itself provide a mechanism for accurately transporting color-managed images across the Internet.

File Format

The JFIF meta data resides in the JPEG Application Segment APP0, having the zero-terminated ASCII string "JFIF" as segment header.

Import Options Dialog

No import options dialog is displayed.

Import Automation Options

No import options are available.

Export Options Dialog

See JPEG Export Options Dialog

See Scaling and Spatial References for additional information.

Export Automation Options

See Image Bitmap Export Automation Options for additional information

Legal Notice

This software is based in part on the work of the Independent JPEG Group.

See Also

File Format Chart