There are programs purely for viewing graphics, but a graphics application program is used to draw and edit images. There two distinct sorts of graphics file and not all programs can manipulate both sorts.
Image you are told to draw a picture but there is catch-you can only use dots on a grid.
You can use as many colors as you like and you can use as many dots as you like, but the picture must be entirely dots. This is one way that graphics program can draw pictures.
Images draw like this are known as bitmap graphics (or ‘ raster graphics’). The application program works by dividing the drawing area into lots of small squares called ‘pictures elements’(or ‘ pixels’).
As the user moves a pointing device representing a pen, brush or spray can of a particular color, the program shades in the selected pixels.
That pictures shows a dog draw using a bitmap, with only 30 squares and in monochrome(black and white). More squares and colors would mean that a better drawing could be made
A bitmap or raster graphics file, such as Microsoft Paint produces, stores the resulting image as a two-dimensional array of numbers that ‘map’ the individual colors of the pixels.
This is the only way of storing digital photographs or scanned images, although bitmap graphics can also be produced by drawing tools.
The information sent to a monitor screen, projector and almost all printers needs to be in the from of a bitmap.
A disadvantages is that as the image is enlarged, eventually the pixels become visible. This is known as ‘ pixellation’.
Other disadvantages are that drawn elements do not retain their identities and so are not independently editable and that data have to be stored for each one possibly millions of pixel, in up to 16 million colors, so the file can be very large.
The other method of drawing pictures is known as vector graphics.
A vector graphics file stores the drawn image as numbers that represent the properties of each graphical object that has been drawn.
The file is usually much smaller than a bitmap graphics file with similar appearance because relatively few numbers are required to recreate the drawn image.
An example of a vector graphic is one you might draw using the drawing toolbar in microsoft word.
When a vector graphics file is enlarged there is no pixellation.
Features of graphics programs may include:
R Drawing tools for lines, geometrical shapes and freeform objects
R Painting tools, such as brush, pencil and airbrush, for bitmaps only
R Input form special hardware
R Separate layers to keep bitmap images editable, to facilitate hiding or locking part of the user`s work while they work on other parts to prevent unintended editing or deletions
R Resize, rotate and flip tools
R Creation of animated graphics
R Exporting data in graphics file formats other than the program`s native format, often with reversible or irreversible compression
A bitmap image drawing program has additional features:
R Selection tools including rectangle, rounded rectangle, ellipse, free and fuzzy
R A foreground extraction tool to remove a figure from its background
R A cropping tool removing unwanted regions from the edges
R Adjustment and automatic correction of brightness, contrast and color
R Photo enhancement using image transformation tools, such as shear and distortion correction, and photo retouching with ‘red-eye’ removal, healing and clone tools.
R Home work
What means a vector graphics? How that method draw in a graphics?
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