Imaging Software Glossary: Terms & Concepts: L
The imaging software glossary provides definitions for document and web imaging, in addition to terminology specific to Snowbound Software’s imaging technology.
| Layer | The layer is the organization of programming into separate functional components that interact in some sequential and hierarchical way, with each layer usually having an interface only to the layer above it and the layer below it. |
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| Library | The library is a collection of software functions that can be called by a higher level program. Most libraries are collections of similar routines such as those used for graphical or image processing. |
| Linear Interpolation | Linear interpolation is used for resizing an image. It takes 2 pixels, separated by x pixels, then averages the x + 2 pixels to create an intermediate value. This resulting value is then used to represent the entire range of pixels. Linear interpolation is not very effective for resizing 1-bit documents since much of the visual data is lost. |
| Look-up-table | A look-up-table is an indexed list of numbers used to change pixel values in a predefined way. A look-up-table is used to determine the colors and intensity values with which a particular image will be displayed. |
| Lossless Compression | Lossless compression is a method of image compression where there is no loss in quality when the image is compressed or uncompressed. Lossless compression is used when it is important that the original and the decompressed data be identical. Some image file formats, notably PNG, use only lossless compression. |
| Lossy Compression | Lossy compression is a method of image compression where some image quality is lost during higher compression. A lossy data compression method is one where compressing data and then decompressing it retrieves data that may well be different from the original, but is close enough to be useful in some way. The advantage of lossy methods over lossless methods is that in some cases a lossy method can produce a much smaller compressed file than any known lossless method, while still meeting the requirements of the application. The most common lossy image compression method is JPEG. |
| LZW | Lempel Ziff Welch (LZW) is a lossless image compression method found in the popular GIF format and patented by Unisys. Two commonly-used file formats in which LZW compression is used are the GIF and TIFF format. LZW compression is also good for compressing text files. It only supports up to 8-bit data. |