Tagged Image File Format (abbreviated TIFF) is a file format for storing images, including photographs and line art. It is now under the control of Adobe Systems. Originally created by the company Aldus for use with what was then called "desktop publishing", the TIFF format is widely supported by image-manipulation applications, by publishing and page layout applications, by scanning, 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, have been based on the TIFF 6.0 specification.
TIFF was originally created as an attempt to get desktop scanner vendors of the mid-1980s to agree on a common scanned image file format, rather than have each company promote its own proprietary format. In the beginning, TIFF was only a binary image format (only two possible values for each pixel), since that was all that desktop scanners could handle. As scanners became more powerful, and as desktop computer disk space became more plentiful, TIFF grew to accommodate grayscale images, then color images. Today, TIFF is a popular format for high-color-depth images, along with JPEG and PNG. Adobe Systems, which acquired the PageMaker publishing program from Aldus, now controls the TIFF specification.
The 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 can be a container file holding compressed JPEG and RLE (run-length encoding) images. A TIFF also can include a vector-based Clipping path (outlines, croppings, image frames). The ability to store image data in a lossless format makes the TIFF file a useful image archive, because, unlike standard JPEG files, the TIFF using lossless compression (or none) may be edited and re-saved without losing image quality; other TIFF options are layers and pages.
Although the currently accepted standard format, when the 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. Resultantly, the TIFF became the lowest common denominator image file. Today, the most TIFF images and readers remain based upon uncompressed 32-bit CMYK or 24-bit RGB images.
The 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 are 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 standardised-consistency problems is Thousands of Incompatible File Formats.
The Tiff file format uses 32bit offsets, and as such, each file is limited to 4 gigabytes.
The TIFF format is the standard in document imaging and document management systems using CCITT Group IV 2D compression, which supports black-and-white (bitonal, monochrome) images. In high-volume storage scanning, documents are scanned in black and white (not in colour or in grayscale) to conserve storage capacity. An average A4 scanning produces 30 KB of data at 200 ppi (pixels per inch of resolution) and 50 KB of data at 300 ppi; 300 ppi is more common than 200 ppi.
The TIFF format can save multi-page documents to a single TIFF file rather than a series of files for each scanned page. Multi-page support and 2D compression of bitonal images led to the TIFF's becoming the standard storage format facsimiles, especially on Fax Servers.
Storing a sequence of images in a single TIFF file is also possible, and is allowed under TIFF 6.0, provided the rules for multi-page images are followed.
Multiple buffer overflows have been found in Libtiff. Some of these have also been used to execute unsigned code on the PlayStation Portable, as well as run third party applications on the iPhone and iPod Touch.