What is a raster: definition, classification, translation into a vector

Any designer knows what a raster is. This is important for preparing images for publication, changing them, creating layouts. For a typical network user, the difference between formats is not that great. However, these are the basics of working with graphics, which everyone must know who wants to be able to process photos.

Definition of a raster, its advantages and disadvantages

What is a raster? This is an image composed of a matrix of pixels, colored with a certain color. They are easy to see, greatly increasing the figure. The file with raster graphics stores the code containing the number of dots and their color. Photos, scanned images, illustrations in magazines and on the computer screen are raster. A grid of pixels (dots) can transmit an image of any complexity, shadows, gradients, blur, halftone, 3D effects and even animation. Photorealism is the main advantage of this kind of graphics.

The disadvantages of raster include the following:

1. Unable to scale. By increasing the image (i.e., stretching the pixel grid) or decreasing it (by pulling it down so that some of the points disappear), you can significantly degrade the picture quality.
2. The bitmap is limited to a rectangle. That is, when overlaying drawings on top of each other, the lower one "hides" under the white background of the upper one.
3. The more complex the image, the more the file weighs with it.

Characteristics of rasters

Bitmap images differ in size, resolution, color modules and the number of hues. The mesh characteristics are also excellent. The following types of rasters are known by the type of matrix: regular and stochastic.

1. Size (weight) - the total number of pixels in the image, is calculated in KB (MB, GB). The bigger and more complex the pattern, the more it weighs.
2. Resolution is the number of pixels per inch (ppi) of Internet pictures, photos or dots per inch (dpi) of printed illustrations. The larger this parameter, the better the picture, the clearer. The standard resolution of Internet images - 72 ppi, printed layouts - 300 ppi.
3. The color module defines the basic shades. This can be a common RGB, when red, green and blue are present in an amount in each pixel and, mixing, form the desired color. To prepare the layouts often use CMYK - a module consisting of cyan, magenta, yellow and black colors. LAB is "light", red-green and blue-yellow; Grayscale - shades of gray.
4. On how many bits are encoded in each pixel, the color of the picture depends. In monochrome images, each point weighs 1 bit. If there is 4 bits in the pixel, the picture consists of 16 colors. 8 bits per pixel give 256 colors, 16 bits - 65 thousand colors, 24 bits - 16 million shades.
5. Distinguish the following types of rasters depending on the matrix of pixels: a regular has a mesh structure (with darkening of dots or a grid), the stokahtical does not have a clear organization, that is, the pixels are located chaotically.

The difference between a bitmap image and a vector

In addition to the raster, there is a vector format - a way of creating a drawing, in which the minimal elements of the image are the simplest geometric figures: rectangles, ovals, circles, straight and curved lines. The vector graphics file contains mathematical formulas - parameters of shapes (diameter, length, width, fill, color, contour), their location on the canvas (X and Y coordinates) and position relative to each other. Vector drawing is easy to scale and edit - you just need to change the characteristics of the desired object. When the image is enlarged or reduced, its quality does not change. The picture in the vector is not limited to a rectangular background - they can be superimposed on each other. At the same time, the original file weighs considerably less than the raster.

With such a number of advantages that such a raster can oppose a vector? Pictures in this format are hard to call realistic - they have a little cartoony display due to the fact that pure colors and gradients are used. Modern graphic editors - Corel Draw, Adobe Illustrator - can work with complex effects: shadows, blending colors, blur, but to the possibilities of processing raster images they are far away. In the vector prepare layouts for printing.

Bitmap graphics formats

Bitmap images can be saved in different formats, and the conversion is simple - you need to open the file with any image editor, select the "Save As" menu item and the desired extension.

GIF is the simplest display format. It supports transparency and animation effects, it weighs a little, but its color is low - 256 colors. In GIF it is convenient to store charts and diagrams.

PNG uses lossless compression and supports transparency, much more colorful than GIF.

TIFF is used to convert from raster to vector, since this format does not combine the layers in the drawing.

JPEG is the most popular format used for photos, scanned images, Internet images.

How to translate from raster to vector format

The need to convert a raster image to a vector appears in the designers when making a layout, or if you want to enlarge the picture, change it without losing quality. Translation into a vector is not a trivial task, since many photo effects can not be reproduced. When auto-tracing, the picture quality is greatly reduced: colors can be distorted, details of the picture may be lost. This automatically creates objects from groups of pixels of similar colors, located on the contour of the raster image. If the drawing is complex, created objects can be very much, and editing them is not easy. Autorouting is available in the Corel Drew or Illustrator editors.

A good quality picture can only be obtained by manual tracing. At the same time, the designer traces the pattern along the contour, and shadows or volume are created by imposing shapes of different sizes and shades on each other. The easiest way to do this is on a graphic tablet, using the stylus to trace the lines. Manually created images in a vector are expensive and highly appreciated.

... and vice versa

Rasterization is a process opposite to tracing, when the vector drawing needs to be translated into a raster, in order, for example, to supplement it with complex photoeffects. In this case, all good properties of the vector disappear, that is, the resulting image can not be scaled without loss of quality. Therefore, it is desirable to save the original file in order to enlarge or change the picture if necessary.

Before transferring to a raster (Convert to Bitmaps), you need to set the following parameters:

1. Color - the number of colors in the picture.
2. Dithered - when this item is activated, colors will be formed by mixing.
3. Redolution - permission.
4. Anti-aliasing - lines and kinks of the original pattern will be smoothed.
5. Trandparent Backgrounf is a parameter that makes the background transparent.
6. Size is the size.

So, for the correct work with the drawings, you need to know what a raster and vector are. A bitmap image is formed from a set of pixels - the smallest graphic elements. Raster is colorful, it reproduces many photo effects, even animation. However, such images are difficult to scale and change. A vector, on the other hand, can easily be altered by changing a drawing object; When scaling, its quality remains the same. However, it is difficult to transmit shadows, blur, complex gradients, and color mixing . The bitmap can be roughly displayed in vector format and vice versa.