Image Types - Raster VS Vector

Raster Graphics

Raster graphics, or bit-mapped graphics, are digital images stored as arrays of pixels for display and modification. In raster data there are no lines, circles, or polygons, only pixels that are grouped to give the appearance of these elements. Because scanned images and photos are saved as raster graphics, it is common for customers to submit images in this format.

The most common challenge with working in raster format is resizing the graphic. Raster graphics are measured by the number of individual pixels per inch of the total graphic when the image is created. For example, if a graphic is created to have 300 pixels per inch and the graphic is 3 inches tall by 2 inches wide, the total graphic will be 6 square inches and will be made up of 1,800 pixels. If you take an image created in this way and attempt to change the overall size to 6 inches by 4 inches, you will now have a 24 square inch image area but you will still only have the same 1,800 pixels with which to cover that area. Because each pixel is intended to cover a very small area and must be stretched considerably to cover the new larger area, the overall quality of the graphic will suffer considerably.

Raster VS Vector

Another challenge of working in raster format is the creation of straight lines. Because raster graphics consist of a series of small circles, it is impossible to ever truly create a straight line. For this reason, things like typed fonts and geometric images are not recommended for creation in raster format. Raster Graphic Software The most commonly used raster graphic art creation program is Adobe Photoshop. Photoshop can be purchased for download and installation, or for a monthly fee, users can access the program via the Internet. In either case, Photoshop allows users to create, edit and print raster graphic artwork.

Vector Graphics

Vector graphics use geometrical primitives such as points, lines, curves, and shapes of which are all based on mathematical expressions, to represent images. Vector graphics are comprised of groups of solid colors and do not contain gradient color shifts. Because of this, images that have a lot of shading are not recommended for use as vector graphics as they will increase the total color count of the image to an unreasonable number.Because vector graphics are based on mathematical expressions, it is easy to resize them. When a vector graphic is resized, the program is able to use information related to the size of the graphic and simply adjust the math to account for the change. Simple resizing is a great feature if you will be creating an image for use on both the front and back of a garment. If you will be printing a 4 by 4 inch image on the front of a shirt and the same image in 12 by 12 inch size on the back, you will need only create the image once and resize it for the different placements. Conversely, if you want to create this image in raster form you would need to create the image twice to ensure that the image quality was the same for both images.

Most vector artwork programs include tools that will allow you to convert an image from raster to vector. When converting images it is important to remember that the quality of the raster image will directly affect the quality of the converted vector image. Images that are of poor quality or are too small will often become distorted during the conversion process and will require that all or part of the image be recreated.

Vector Graphic Software

There are two vector graphic software products on the market today that the vast majority of printers will use. The first product is Corel's Draw program, most commonly just called Corel Draw. Corel Draw is a simple and inexpensive software that packs in a plethora of useful tools. It is important to keep in mind however that Corel Draw is not compatible with Apple Macintosh computers.

The second option for vector graphics software is Adobe Illustrator. Like Photoshop, Illustrator is available for purchase and download and is also available as an online application with a monthly subscription. Illustrator is great for people that like to use Photoshop for their raster needs because it has a similar look and feel. Another great feature of Illustrator is that it is compatible with both Mac and PC hardware. Regardless of the software you choose, you will be glad that you have a good vector program.

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