JFIF
From Just Solve the File Format Problem
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| + | == Overview == | ||
'''JFIF''' (JPEG File Interchange Format) is a standard that defines a portable subset of the [[JPEG]] interchange format. Most of the JPEG files in existence conform to JFIF. | '''JFIF''' (JPEG File Interchange Format) is a standard that defines a portable subset of the [[JPEG]] interchange format. Most of the JPEG files in existence conform to JFIF. | ||
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* The image has a particular orientation. | * The image has a particular orientation. | ||
* If the image is subsampled, it uses a particular subsampling position. | * If the image is subsampled, it uses a particular subsampling position. | ||
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| + | == Identification == | ||
| + | Valid JFIF files begin with <code>FF D8 FF E0 ?? ?? 'J' 'F' 'I' 'F' 00</code>. Some technically-invalid files exist in which the JFIF segment has been relocated, and for them this signature will not match. | ||
== History == | == History == | ||
Revision as of 18:51, 3 March 2013
Contents |
Overview
JFIF (JPEG File Interchange Format) is a standard that defines a portable subset of the JPEG interchange format. Most of the JPEG files in existence conform to JFIF.
JFIF defines JPEG application segments which serve to identify JFIF files, and to store a small amount of metadata: the pixel density, and a thumbnail image.
The presence of a JFIF segment implies that:
- If the image has three components, its color format is YCbCr. If it has one component, its color format is grayscale.
- The image has a particular orientation.
- If the image is subsampled, it uses a particular subsampling position.
Identification
Valid JFIF files begin with FF D8 FF E0 ?? ?? 'J' 'F' 'I' 'F' 00. Some technically-invalid files exist in which the JFIF segment has been relocated, and for them this signature will not match.
History
- JFIF 1.00 (PRONOM: fmt/42) was the original version.
- JFIF 1.01 (December 10, 1991; PRONOM: fmt/43) may have changed the subsampling position to centered.
- JFIF 1.02 (September 1, 1992; PRONOM: fmt/44) added an optional JFXX segment, capable of storing a compressed thumbnail image.
Specifications
- JFIF version 1.01
- JFIF version 1.02
- ITU Recommendation T.871
