(b) TIFF image format
TIFF is the most complicated bitmap file format. TIFF is a tag-based file format that is widely used for the storage and conversion of images with high image quality requirements. Due to its flexible and inclusive structure, it has become a standard for image file formats. Most image systems support this format.
1. File Structure Overview TIFF files have a .tif extension. Its data format is a three-level architecture, from high to low, in order: file headers, one or more directories and data called IFDs containing tagged pointers.
(1) File header (IFH). The first data structure in each TIFF file is called the image file header or IHF, which is the highest layer of the image file architecture. This structure is unique in a TIFF file and has a fixed location. It is located at the beginning of the file and contains the necessary information to properly interpret the rest of the TIFF file.
(2) Image File Directory (IFD). IFD is the second data structure in a TIFF file. It is a table called a tag to distinguish one or more variable-length data blocks. The tag contains all the information about the image. The IFD provides a series of pointers (indexes) that tell us where each of the relevant data fields begins in the file and gives the data type and length of each field. This method allows the data field to be located anywhere in the file and can be of any length, so the file format is very flexible.
(3) Image data. According to the address pointed to by IFD. Store related image information.
2. TIFF image format features (1) a wide range of applications. 1TIFF can describe many types of images; 2TIFF has a series of compression schemes to choose from; 3TIFF does not depend on specific hardware; 4TIFF is a portable file format.
(2) TIFF is extensible. Many extensions are defined in TIFF 6.0. They allow TIFF to provide the following general functions: 1 several main compression methods; 2 more color representation methods; 3 image quality enhancement; 4 special image effects;5 document storage and retrieval assistance.
(3) The format is complicated. The complexity of the TIFF file brings some problems to its application. On the one hand, it is very difficult to write software that can identify all the different tags. On the other hand, a TIFF file can contain multiple images, each with its own IFD and a series of tags, and uses a variety of compression algorithms. This also increases the complexity of the programming.
3. Summary TIFF has nothing to do with the structure, operating system and hardware of the computer. It can handle black and white, grayscale, and color images, allowing users to debug the unique capabilities of a scanner, monitor, or printer. Its format extensibility is strong. For data exchange between media, TIFF is one of the best choices for bitmap mode. However, it also requires a lot of programming to achieve full decoding. At present, the TIFF image format has become a main image format in the prepress system. (to be continued)