What graphic formats are used in web - design?exist rather large number of various formats of graphic files Now. Nevertheless, everything them can be divided into two groups. These are the files storing the vector graphics and files storing raster graphics.
The raster graphics is when the image is stored in a type of small points - pixels. Respectively quality of such picture is limited to two factors: it is actually the size of the picture in pixels, and permission of the image - that is the number of pixels per unit length (it is most widespread pixels per inch). The files storing raster graphics it is of jpg, gif, bmp, tiff, png, psd and other.
The vector graphics is when the image is stored in a view of the massif of the numbers describing creation of the image in the form of curve and key points - tops. Formats of vector graphics - of swf, cdr, max, ai, partially pdf. by
in practice of web of graphics generally use two formats of raster graphics - of jpeg and gif , and one format of vector graphics - of swf . The png format is much less often used .
The jpeg and gif formats differ with various algorithms of compression of the image. As in web the file size still plays very essential value for a variety of reasons, therefore, the small weight of the graphic file significantly increases the speed of loading of the image. For different “ types “ pictures this or that format of graphics approaches.
Definition of a necessary format - a basic skill of web - the designer. The jpeg format best of all is suitable for photos, portraits, pictures of the big size sated with difficult details - .
Algorithm of compression of this format works in such a way that at reduction “ weight “ pictures, and consequently qualities, image as if “ it is washed away “ accurate transitions between flowers become badly distinguishable, and parasitic color pixels as a side effect of action of algorithm appear. Degree of a compression of the file is defined every time by the designer proceeding from his needs, but size / quality of the image is considered an optimum ratio the compression percent equal 65.
The gif format in the best way is suitable for images of the small size, there where transparency (an alpha - the channel), and is necessary for the animated raster graphics.
Algorithm of compression of this format is based that to the image the fixed color palette (from 2 to 256 flowers) is set, and all close shades are thrown out or replaced in the next flowers. Also the algorithm counts the image lines - from left to right, and stores information not about each pixel separately, and considers how many pixels of identical color stand in a row, and saves information only on color and the number of pixels. It significantly loses file weight. It is easy to notice that the vertical gradient (from above - down) will weigh in that case much less gradient horizontal (at the left - to the right). It should be considered during creation of images, especially during creation of the animated banners where weight consists also of quantity of frames and there is literally a war for each byte.
The png format is used extremely seldom. Its difference from the gif format that of png allows to store more information on the file. In particular, information about an alpha - the channel. In the gif format each separate pixel can be either completely transparent, or completely opaque. It imposes restrictions for use of transparent transitions to transparency because of what the gif files with transparency often look “ fragmentary “ at the edges. But, in connection with the big weight of png of files, they are practically not used, and apply various visual cunnings in the gif format , in particular addition “ transitional “ pixels at the edges of the image.
At a name of files it is necessary to follow the simple rules. In - the first, it is necessary to avoid as senseless, and “ speaking “ names. The name of the file has to define its place in structure a web at once - pages. That is, if it is the picture to article, then it has to settle down in the articles folder and as its name serves article id. If it is a position in the catalog, then in the corresponding folder (items, groups) the picture has to have the name ID of group, subgroup or goods.
At the same time if, for example, on the website articles are very seldom written, it is possible not to enter additional folders, but then the file has to be associated unambiguously according to the name with this section. It can be made for example addition of the word news or art before picture id ( for example news - 34. jpeg ). If several pictures of the different size belong to one id - it is necessary to add after picture id the expansion designating the size (for big pictures - b, for small - s) ( an example 38 - s. gif, art - 08 - b. jpeg ). For several pictures of one size, it is possible to enter serial numbers (an example: art08 - b_01. gif).
At a name of the pictures forming registration of the website it is necessary to adhere to the following designations: top - for a cap of the website, bottom - for the cellar of the website, but - for different buttons, ico - for icons, img or pic - for other pictures of registration with addition of serial number at the end.
As the main programs for work with images at the designer serve Adobe Photoshop and Adobe ImageReady for raster graphics; Corel draw and Macromedia Flash for vector. Also the Adobe illustrator program - but it already a matter of taste of the designer because programs are in essence identical is used by time for vector graphics, and have similar functionality. All products of Adobe firm (and Flash belongs to them also recently), possess similar tools and the hot keys that simplifies work in different programs upon transition from one to another.
The flash format - one of most “ fashionable “ and popular in a web. To it serves several its features. In - the first because it is a vector format, creation of rather difficult and colourful images is possible with rather small weight of the file. In - the second, due to use of the built-in scripting Action Scrip language t in flash is an opportunity to create interactive banners, applications, to write various scenarios, to create online of system of calculation, game, stand-alone programs, etc.