Tagged Image File Format (abbreviated TIFF) is a file format for storing images, includingphotographs and line art. It is as of 2009 under the control of Adobe Systems. Originally created by the company Aldusfor use with what was then called “desktop publishing”, the TIFF format is widely supported by image-manipulation applications, by publishing and page layout applications, byscanning, faxing, word processing, optical character recognition and other applications.Adobe Systems, which acquired Aldus, now holds the copyright to the TIFF specification. TIFF has not had a major update since 1992, though several Aldus/Adobe technical notes have been published with minor extensions to the format, and several specifications, including TIFF/EP and TIFF/IT (ISO 12639)have been based on the TIFF 6.0 specification.
Flexible options
TIFF is a flexible, adaptable file format for handling images and data within a single file, by including the header tags (size, definition, image-data arrangement, applied image compression) defining the image’s geometry. For example, a TIFF file can be a container holding compressed JPEG and RLE (run-length encoding) images. A TIFF file also can include a vector-based Clipping path (outlines, croppings, image frames). The ability to store image data in a lossless format makes a TIFF file a useful image archive, because, unlike standard JPEG files, a TIFF file using lossless compression (or none) may be edited and re-saved without losing image quality. Of course this is not the case when using the TIFF as a container holding compressed JPEG. Other TIFF options are layers and pages.
Although the currently accepted standard format, when TIFF was introduced its extensibility provoked compatibility problems. Programmers were free to specify new tags and options — but not every implemented program supported every tag created. As a result, TIFF became the lowest common denominator image file. Today, most TIFF images and readers remain based upon uncompressed 32-bit CMYK or 24-bit RGB images.
TIFF offers the option of using LZW compression, a lossless data-compression technique for reducing a file’s size. Until 2004, this option’s use was limited, because the LZW technique then was under several patents; however, these patents have expired.
Every TIFF begins with a 2-byte indicator of byte order: “II” for little endian and “MM” for big endian byte ordering. The next 2 bytes represent the number 42, selected “for its deep philosophical significance”. The 42-reading depends upon the byte order indicated by the 2-byte indicator. All words, double words, etc., in the TIFF file are read based per the indicated byte order. The TIFF 6.0 Specification (Section 7: Additional baseline TIFF Requirements) says that compliant TIFF readers must support both byte orders (II and MM), however, TIFF writers may choose the byte order convenient for their image. The image-processing community’s joke about the early TIFF’s standardized-consistency problems is Thousands of Incompatible File Formats.
The TIFF file format uses 32-bit offsets, and as such, file size is limited to 4 GiB (4,294,967,296 bytes).
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