The best way to describe the scanning process is to explain the steps involved in converting a photographic print to a Windows DIB (Device Independent Bitmap). The DIB format is the standard format for all Windows bitmaps—it is the recommended target format for all your bitmapped images.
Each image starts out as a separate photographic print with its own unique palette. The process of getting an image ready for the final application goes something like this:
Your images may look great on your display, but if your production monitor is improperly adjusted the final image may not look right when displayed on other monitors. Since you can never be sure how well adjusted the delivery system monitor will be, make sure you have at least created the image in the truest, most accurate color.
The best way to adjust a production monitor is to buy a color bar generator that outputs pure RGB and plug it directly into your monitor. You can also look for software that generates a color bar, and then adjust your monitor settings accordingly. Without these tools, adjustments are purely subjective as they rely solely on your ability to visually evaluate color.
Many scanners offer several image-depth settings. Because Windows with Multimedia supports 1-bit, 4-bit, and 8-bit bitmaps, any palette can contain up to 256 unique colors. The quality of a scanned bitmap depends on how well a system can re-create the effect of a continuous-tone image using these 256 colors. Whenever possible you should always create and enhance bitmaps using large image depths.
Good color scanners can scan with a color resolution of up to 24 bits per pixel, allowing 16 million colors in the palette. Most scanning programs let you reduce the colors in the image from 24 to 8 bits or less. If you want to scan an image once and store the highest quality image possible, scan it at 24 bits and reduce it after you're totally satisfied with the results. If you don't need the original high-quality image, you might as well reduce it as you scan, since it will require far less space to store.
Set the size or resolution of the screen image by specifying the number of dots per inch (DPI) in the image. Adjust the DPI setting (sometimes called the scanning resolution) to be as close to the desired image size as possible. VGA screens with 640 by 480 resolution display images at about 72 DPI; a scan setting of 72 DPI produces approximately a 1:1 ratio in size.
You control the size of the screen image with the scanning resolution. To shrink the screen image of an illustration, set the scanning resolution to less than 72 DPI. To enlarge the screen image, set the scanning resolution to greater than 72 DPI.
A quick way to determine the desired scanning resolution is to divide the number of pixels you want to cover on the screen in one dimension by the same dimension of the area of the picture you want to use. For example, say your original image is 10-by-8 inches and you want it to fill half the screen (320 by 240). Divide 320 by 10 and you obtain a scanning resolution of 32 DPI.
Hint:
Although paint programs allow you to resize images, building a digitized image of the correct dimensions with the digitizing software gives you a better image. Paint programs make intelligent guesses when reducing or enlarging an image. In contrast, digitizing software doesn't guess; it uses information from the original illustration to build the digitized image.
Always pre-scan the image. Pre-scanning takes only a few seconds and provides a quick, low-resolution scan of the entire scanning bed. Pre-scanning your image lets you set cropping boundaries for the digitizing software and saves time during scanning. Pre-scanning is present in all decent capturing programs.
After pre-scanning, eliminate the portion of the picture you don't want. This not only limits the size of the image file, it also reduces the total number of colors included in its color palette. Since you'll probably have to adjust the image's palette if you want to display it with other images, a smaller palette can simplify this process.
Now scan in the image. After you've scanned the image, look at it and see what adjustments you might like to make. Scanner software sometimes includes a paint or draw package to clean up any problems introduced during the scan. If you have the time, cut out all unnecessary elements of each image, especially in the background. Again, this makes for a smaller image file and a smaller palette.
If you capture digital images on a different computer than your multimedia application development system, you'll need to transfer your images to the development platform. There are several ways to move images from one system to another, but using a network is probably the fastest and most efficient method if you are moving lots of large files, such as images.