Computer Graphic Images
Graphic images that have been processed by a computer can usually be divided into two distinct categories. Such images are either bitmap files or vector graphics.
Bitmap is a representation, consisting of rows and columns of dots, of a graphics image in computer memory.
Also called a raster image, the bitmap image is made of pixels or dots that are arranged and colored differently to form an image or pattern such as a photograph. For simple monochrome images, one bit is sufficient to represent each dot, but for colors and shades of gray, each dot requires more than one bit of data. The more bits used to represent a dot, the more colors and shades of gray that can be represented.
When you zoom in, you can see the individual squares that make up the total image. Increasing the size of a bitmap has the effect of increasing individual pixels because extra pixels are added that did not originally exist, making lines and shapes appear jagged and/or distorted. Reducing the size of a bitmap also distorts the original image, because pixels are removed to reduce the overall image size and quality.
A graphic representation of a bitmap image can be seen on the next image. The right image is 300 percent enlarged of the area selected from the original picture. The image consists of hundreds of rows and columns of small elements that all have their own color. One such element is called a pixel-short for picture element. The human eye is not capable of seeing each individual pixel so we perceive a picture with smooth gradations.
Bitmap images are resolution dependent. Resolution refers to the number of pixels in an image and is usually stated as dpi (dots per inch).
Bitmap images are displayed on your computer screen at screen resolution: 72 or 96 dpi, but printed in high resolution postscript printers at 600-1200 dpi, and color separated for Offset, Digital, Screen or Pad printing at 1200-3600 o more dpi. Unless the image you probably see right on your computer monitor contains the resolution required to output high resolution plates from the graphic arts equipment, output will looks jagged or distorted. Because a bitmap image is created as a collection of arranged pixels, its parts cannot be manipulated individually. Bitmaps have a fixed resolution so a bitmap looks best when you display or print it at its original size.
Bitmap images are opened and manipulated in software programs like Adobe Photoshop and Corel Photo-Paint.
The following is a black and white image at 300 dpi resolution, and represents a company logo. Because Promotional Products Industry uses high resolution printers and plate setters, those lines you could see even on your computer monitor are printed more like the enlarged portion of image, where it's clearly notable how edge cuts unevenly.
Using bitmap images in the Graphic Arts and Promotional Products Industry
The bitmap image plays an important role in the Graphic Arts and Promotional Products industry. Digital pictures, photos, transparencies, etc. which will be printed in full process color are normally bitmap images. Bitmap images are transferred to the computer by taken it digitally, or by means of scanning a previously taken picture. When the picture is transferred from a digital camera or scanned directly into the graphic software, it's converted from RGB to CMYK format. The CMYK is the format used in the Promotional Products industry and it stands for Cyan, Magenta, Yellow and Black.
Bitmap images are used in the Promotional Products industry for printing full color designs in Calendars, Christmas Cards, T-shirts, Mouse Pads, Bags, Bumper Stickers, Decals, Magnetic Business Cards, Ceramic Coffee Mugs, 3-M Post-It Notes, Scratch Pads, Full Color Magnetic Car Signs, Banners, Posters, and some Pens, Flashlights and Office Accessories using Digital Printing technology.
Bitmap images are not recommended and cannot produce a high quality printing job for printing logos and designs in one or more spot colors. In such cases, a vector file is required.
Vectors are a way of defining images on a computer and are defined by points and curves rather than by pixels. They are scalable and therefore are not resolution dependent. Vector graphics are made up of independent objects, each of which can be individually selected, sized, moved and manipulated, which gives the Graphic Arts and Promotional Products industry outstanding advantages for image manipulation. The vector graphic is created through a sequence of commands or mathematical statements that place lines and shapes in a two-dimensional or three-dimensional space. Vector elements are graphical objects that have a precise direction, length, and shape and can be points, lines, polygons, arcs, rectangles, circles, text, ellipses, elliptical arcs, arc wedges, elliptical arc wedges, and symbols.
Vector graphics primarily originate from software and is prepared in a vector-drawing program and is based on PostScript® page-description language. A designer "plots" vector points and the points are connected with straight or curved lines. The shapes can be filled with a color, a gradient, a pattern or nothing at all. Because a vector image uses PostScript language, the image scales perfectly.
Following images are representations of the bitmap image, the bitmap image with the anti-aliased transition applied (used some times to overcome the appearance) and the smooth vector image.
Smooth Vector Graphic
Use of Vector Graphics in the Graphic Arts and Promotional Products Industry
Vector graphics is the format for logos and other computer graphics except photographs. Because it's scalable capability, vector graphics are the best option to create logos and graphics and use it to print promotional products. By creating initially your corporate logo in a vector software program, it can be used for all purposes in the future. The vector file could be used by printers and promotional products companies to achieve a high quality printing. Once you have created your vector logo, it can be easily converted to a bitmap format for web presentations, CD catalogs, and other low resolution requirements. It's important to understand the conversion process is irreversible, so always keep an original copy of the vector file.
New graphic technology allows more full process color material than before. Some companies are taking advantage of this technology and are using more and more printing products in full color. For such cases, your graphic designer could make a full color version of your logo. This high resolution bitmap version can be close to the vector counterpart, and provides extra benefits by using a high quality logo for these materials.
Computer graphics are essentials to properly identify companies, products or services. Each of these two major types of graphic formats is important to the Graphic Arts and Promotional Products industries. Each format conforms to special requirements and necessities according to the printing process to be done, helps other one in filling these holes commonly found, and both together helps the graphic designer and promotional products community to create a complete sets of options and be able to provide professional presentations and promotional material.