Sind alle JPEG-Dateien JFIF?

Question

Active Directory kann Bilder im JPEG File Interchange Format (JFIF) gemäß dem jpegPhoto Attribut Definition . Ich möchte dies benutzen, aber ich habe noch nie davon gehört JFIF.

Zunächst werden alle JPEG-Dateien JFIFs?

Zweitens, eine WPF JpegBitmapEncoder eine JFIF-Datei erzeugen? Ich denke, wenn die erste wahr ist, dies sein wird, aber wenn es nicht ...?

Answer 1

JPEG = the compression algorithm (Joint Photographic Experts Group)

JFIF = the file format (JPEG File Interchange Format)

Effectively when you mention jpeg/jpg you are actually talking about JPEG/JFIF, although there is a spec for JPEG/TIFF and JPEG/EXIF (usually digital photos is where you'll see these)

A lot of the time whatever produces the EXIF file will also include what JFIF parsers need to decode properly, so it is transparent to the end user, but not entirely a "valid" and "to spec" EXIF file.

For internet use and transmission the default is JFIF, but not all jpegs are necessarily JFIF when you look under the covers.

Answer 2

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. So all JPEGs are JFIF.

Answer 3

I've checked Wikipedia. Apparently, JFIF is a more detailed subversion of the JPG format.

More details here...

Also, it seems that JpegBitmapEncoder supports different codecs. Thus it could be that you use a Codec that does (or does not) create JFIF files. You would have to check the codec for this.