A digital image is made up of pixels arranged in a rectangular grid. For this reason, the size of an image is usually described in terms of the size of the pixel grid, for example 1280 x 800, which means 1280 pixels horizontally by 800 pixels vertically, giving a total of 1280 × 800 = 1024000 pixels or 1.024 mega-pixels. The higher the number of pixels an image has, the higher the level of detail it can contain. This is referred to as resolution and is normally used as a measure of image quality, although it is possible for an image with a large number of pixels to be of poor quality if the pixels are not used efficiently.
Pixels do not have a specific physical size attached to them, which in turn means that digital images do not have a definite physical size and may therefore be reproduced at any size. When a digital image is reproduced by way of printing, it is often desirable to have a specific physical size attached to it to govern the size of the print-out. This is done by adding information that indicates the physical area that should be covered by each pixel. The most common way of doing this is adding a parameter that indicates how many pixels should be fitted into a specific area, for example, “200 pixels per inch”.
Setting the Size
In Chasys Draw IES, image size is set using the dialog box shown below. It allows you to set the size in several ways: you can specify the pixels dimensions directly or choose a physical size and a PPI setting and have the pixel dimensions selected for you automatically, you can also set it as a percentage of the current size or you can pick a preset value from a long list of standard paper and screen sizes:
The user interface supports automatic calculation, so you can enter math equations instead of actual values, for example 2*(1024+16). Additionally, it automatically detects standard paper and screen sizes and displays their names at the bottom to guide you.
