Description
Unlike most of the other elements in Arbortext IsoDraw , image elements contain raster data, as described earlier. These are usually the result of a manual illustration or a photo being scanned in and saved as a TIFF or BMP file, for example. They may, however, originate from a drawing or image processing program.
Image elements are distinguished by the attributes of their pixel data. In other words, the appearance and quality of the printout are defined by the image type, resolution and size.
Image Type
There are three different types of image elements which you generally specify during the scanning stage. These are
Line-art images
Line-art images contain only black and white pixels. They are best suited for scanned illustrations which are to be electronically processed at a later stage.
Grayscale images
Grayscale imagescan only contain pixels with gray values. It is possible to have up to 256 different gray values. Photos are normally scanned as grayscale images.
Color images
In color images, the number of colors that can be used depends on the bit depth. The bit depth governs how much memory an individual pixel can occupy. 8-bit images can generate 256 colors, while 16-bit or 24-bit images can generate from several thousand to 16.7 million different colors.
Resolution and Size
When you scan an image, you define the quality of the scan in terms of its detail by the resolution you choose. The resolution specifies how many dots are scanned per inch (dpi = dots per inch). The higher the resolution, the better the quality of the printout - but only if the printer is capable of producing this high resolution on paper.
The size of the file increases rapidly as you increase the resolution. For this reason, you should make sure that you choose an appropriate resolution for the quality you require.
Take, for example, a photograph 100 mm wide scanned at 300 dpi. If you change the resolution subsequently, the size will also change and vice versa. It is thus possible to enlarge the size of the displayed image to a width of 200 mm, for example. Doubling the width halves the resolution to 150 dpi.
