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Figure 9. 3 - Fractal graphics

9.3.1 BIT-MAPPED GRAPHICS

The principle of coding graphic information in a bit-mapped graphics have been discovered
and used by people for many centuries before computers, monitors and scintiscanners. These
principle drawing "on cells" are productive methods of transferring the image from a preparatory
cardboard on the wall, intended for a fresco. Such directions of monumental and applied art, as a
mosaic, stained-glass window, embroidery: in each of these technics the image is made from
discrete and coloured elements as a rule.
A computer bitmapped image is represented in the form of rectangular matrix, every cell of
which is represented by a coloured point. Being digitised the images is divided into such little cells,
that man’s eye does not see them, perceiving the whole image as a unit. A scale got its name of a
raster card, from the English word «bitmap», and its single element (a square cell) is named a pixel
(from English PICture ELement). A pixel is the smallest element bitmap display which has the
address. A bitmap card is a set (array) of three of numbers: two first values are the co-ordinates of
pixel on a plane, the third determines its color. With the help of bit-mapped graphics it is possible to
represent and pass all range of nuances and thin effects, the real image possesses. Bitmapped image
is near to the picture as it allows precisely reproduce basic descriptions of a picture: luminosity,
transparency and depth of sharpness.
According to the structure bitmapped images consist of great number of small coloured points.
Every pel, as a pebble in a mosaic, is independent from each other. However, the amount of colors
in nature is endless, similar colors are numbered by identical numerals. In dependence of the
amount of used colors, it is possible to code a more or less realistic image. It is clear, that less colors
are in the picture, less numbers are used, and it is more simple to code the image. Only black and
white colors are used in the most simple case. For representation of every pixel in a black-and-white
picture one bit is enough. A bit is minimum unit of computer’s memory which can keep a value 0 or
1. While working with color it is obviously not enough. However approach to the coding of the
colored images remains unchangeable. Any picture is broken up to pixel, i.d. small parts, each of
them has its color. The amount of information which describes color of a pixel determines the depth
of color. The more information determines color of every point in a picture, the more variants of
color exists. If we set the size of a pixel, we can restore the coded picture without any problems.
Without defining the size of a pixel, it is impossible to make an image on the basis of the coded
information. However the sizes of pixels are not used in practice, but two other sizes are set: size of
picture and its discriminability. A size describes physical sizes of an image, i.d. its height and
width. It is possible to set sizes in meters, millimetres, inches or any other sizes. But in computer
graphics a size is usually set in pixels. Being reflected on the monitor and typed on the printer every
pixel appears as a separate point, if the equipment does not do any special transformations. Old
monitors, with large grain of kinescope, shows a big picture, and on the modern printer which uses
small points, a picture will be very little. And what kind of picture must be in fact? The
discriminability of an image is set up for this purpose. A discriminability is a closeness of placing
pixels which form an image, i.d. the an amount of pixels on the set segment. More frequently all a
discriminability is measured in the amount of points on an inch - dpi (Dot Per Inch). To reflect

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