Материалы для проведения занятия иностранного языка на тему : "Графические форматы"

Image file formats

Image file formats are standardized means of organizing and storing digital images. Image files are composed of digital data in one of these formats that can be rasterized for use on a computer display or printer. An image file format may store data in uncompressed, compressed, or vector formats. Once rasterized, an image becomes a grid of pixels, each of which has a number of bits to designate its color equal to the color depth of the device displaying it.

rasterize - растеризовать, преобразовывать в растровый формат                     store – хранить

uncompressed – распакованный                compressed – сжатый                      grid – сетка, решетка

Generally speaking, in raster images, Image file size is positively correlated to the number of pixels in an image and the color depth, or bits per pixel, of the image. Images can be compressed in various ways, however.

Compression uses an algorithm that stores an exact representation or an approximation of the original image in a smaller number of bytes that can be expanded back to its uncompressed form with a corresponding decompression algorithm. Considering different compressions, it is common for two images of the same number of pixels and color depth to have a very different compressed file size. Considering exactly the same compression, number of pixels, and color depth for two images, different graphical complexity of the original images may also result in very different file sizes after compression due to the nature of compression algorithms. With some compression formats, images that are less complex may result in smaller compressed file sizes. This characteristic sometimes results in a smaller file size for some lossless formats than lossy formats. For example, graphically simple images (i.e. images with large continuous regions like line art or animation sequences) may be losslessly compressed into a GIF or PNG format and result in a smaller file size than a lossy JPEG format.

Vector images, unlike raster images, can be any dimension independent of file size. File size increases only with the addition of more vectors.

color depth – глубина цвета                       compression – сжатие

representation – изображение                    approximation – приблизительное соответствие

expand – расширять, увеличивать             corresponding –соответствующий

decompression – распаковка, восстановление (сжатых файлов)

complexity – сложность                              lossless – не имеющий потерь, без потерь

lossy – с потерями                                        i.e. – т.е.

region – пространство, область                  line art – штриховой рисунок

sequences – ряд, очередность, серии          GIF (Graphics Interchange Format) 

PNG (Portable Network Graphics)               JPEG (Joint Photographic Experts Group)

dimension – размер, величина, объем, измерение                       independent – независимый

There are two types of image file compression algorithms: lossless and lossy.

Lossless compression algorithms reduce file size while preserving a perfect copy of the original uncompressed image. Lossless compression generally, but not always, results in larger files than lossy compression. Lossless compression should be used to avoid accumulating stages of re-compression when editing images.

Lossy compression algorithms preserve a representation of the original uncompressed image that may appear to be a perfect copy, but it is not a perfect copy. Often lossy compression is able to achieve smaller file sizes than lossless compression. Most lossy compression algorithms allow for variable compression that trades image quality for file size.

lossless compression - сжатие (информации) без потерь

lossy compression - сжатие (информации) с потерями

reduce - сокращать, уменьшать                 preserve – сохранять

avoid – избегать                                           accumulate – накапливать; увеличиваться

stage – стадия, ступень, этап                      edit – редактировать

appear – выглядеть, казаться                     achieve – достигать              trade – менять(зд.)

Including proprietary types, there are hundreds of image file types. The PNG, JPEG, and GIF formats are most often used to display images on the Internet. These graphic formats are separated into the two main families of graphics: raster and vector. In addition to straight image formats, Metafile formats are portable formats which can include both raster and vector information. Examples are application-independent formats such as WMF and EMF. The metafile format is an intermediate format. Most Windows applications open metafiles and then save them in their own native format.

proprietary – собственнический, патентованный           raster – растровый   vector – векторный

metafile - метафайл (файл, используемый для создания изображений, независимых от устройств, такой файл хранит не само изображение, а команды GDI, используемые при его создании)

portable – малогабаритный, портативный                       intermediate –переходный, промежуточный

WMF / EMF (Windows Metafile / Enhanced Metafile)

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