Image Formats

JPEG/JFIF, JPEG 2000, TIFF, GIF, PNG

JPEG / JFIF:

JPEG (Joint Photographic Experts Group) is a compression method; JPEG-
compressed images are usually stored in the JFIF (JPEG File Interchange Format)

file format. JPEG compression is (in most cases) lossy compression. The JPEG/JFIF

filename extension is JPG or JPEG. Nearly every digital camera can save images

in the JPEG/JFIF format, which supports 8-bit gray scale images and 24-bit color

images (8 bits each for red, green, and blue). JPEG applies lossy compression to

images, which can result in a significant reduction of the file size.

JPEG 2000:

JPEG 2000 is a compression standard enabling both lossless and lossy storage.

The compression methods used are different from the ones in standard JFIF/JPEG;

they improve quality and compression ratios, but also require more computational

power to process. JPEG 2000 also adds features that are missing in JPEG. It is not

nearly as common as JPEG, but it is used currently in professional movie editing and

distribution (some digital cinemas, for example, use JPEG 2000 for individual movie

frames).

TIFF:

The TIFF (Tagged Image File Format) format is a flexible format that normally saves

8 bits or 16 bits per color (red, green, blue) for 24-bit and 48-bit totals, respectively,

usually using either the TIFF or TIF filename extension. TIFF's flexibility can be

both an advantage and disadvantage, since a reader that reads every type of TIFF file

does not exist. TIFFs can be lossy and lossless; some offer relatively good lossless

compression for bi-level (black & white) images.

GIFF:

GIF (Graphics Interchange Format) is limited to an 8-bit palette, or 256 colors. This

makes the GIF format suitable for storing graphics with relatively few colors such as

simple diagrams, shapes, logos and cartoon style images. The GIF format supports

animation and is still widely used to provide image animation effects. It also uses a

lossless compression that is more effective when large areas have a single color, and

ineffective for detailed images or dithered images.

PNG:

The PNG (Portable Network Graphics) file format was created as the free, open-
source successor to GIF. The PNG file format supports 8 bit paletted images (with

optional transparency for all palette colors) and 24 bit truecolor (16 million colors) or

48 bit truecolor with and without alpha channel - while GIF supports only 256 colors

and a single transparent color. Compared to JPEG, PNG excels when the image has

large, uniformly colored areas. Thus lossless PNG format is best suited for pictures

still under edition - and the lossy formats, like JPEG, are best for the final distribution

of photographic images, because in this case JPG files are usually smaller than

PNG files. The Adam7-interlacing allows an early preview, even when only a small

percentage of the image data has been transmitted.