To "scan" an image (or "digitize" is) is to turn a physical image (e.g., an illustration in a book) into a digital image (i.e., one that can be posted on the web, used in a PowerPoint presentation, or inserted into a word-processing document).

Before You Scan

Be aware that the image might already exist digitally. Search for existing digital images in the

• Google Image Search at http://www.google.com (click on the Images tab);
• databases licensed for use by UVa, such as AMICO, which are available via the "Databases" link at http://www.lib.virginia.edu; and
• sources listed at http://www.lib.virginia.edu/images.html.

Where to Scan

There are image scanners available for public use located in

• the Bryan Hall public computer lab on the second floor;
• the Electronic Text Center on the third floor of Alderman Library;
• the Digital Media Lab on the third floor of Clemons Library (attached to Macs); and
• other locations listed at http://www.itc.virginia.edu/labs/microlabresource.html.

Some Digital Image Terms

A digital image is composed of thousands of pixels, or dots of a single color. A digital image's resolution is measured in terms of dots per inch (dpi ). The higher an image's resolution, the larger the file size (measured in kilobytes [Kb] and megabytes [Mb]), will be.

An image's resolution should be kept as small as possible to keep file sizes small. When an image's resolution is too low, however, the pixels can become separately visible. Such an image is pixelated, as in this example. 

A Note About Scanners and Scanner Software

Most scanners at UVa are attached to computers which have the image-manipulation software program Adobe Photoshop installed, but there are many different scanning progams [e.g., HP DeskScan] that are used in conjunction with Photoshop. The settings described below, however, are common to all scanning programs. Look for these settings (with perhaps slightly differing names) in the program you are using.

How to Scan (using Photoshop on a computer running Windows)

Place the page on the scanner in the upper right-hand corner. If the page is in a book, make sure it is as flat as possible.

Double-click on the Adobe Photoshop (or other software) icon.

Choose File --> Import [Scanner software]. The latter command might appear as "TWAIN_32"; "HP DeskScan"; or any of several other possibilities. Photoshop, which is primarily an image-manipulation program, must issue an "import" or "acquire" command to another software program that runs the scanner.

At this point, when the scanner software is first launched, there are two decisions to be made.

How many colors does this image need?

Images can be of four basic types or modes:

• Full color / sharp (millions of colors) / 24-bit color. This setting indicates a full color image; it will create the largest file size. It is the most common color setting for color photos and illustrations.
• Indexed color / 256 colors / 8-bit color. This setting uses only 256 colors, but creates a smaller file size. It is appropriate for simple cartoons and logos.
• Grayscale / 8-bit grayscale. This setting uses 256 colors: black, white, and many shades of gray. It is used for black-and-white photos and for images of text.
• B & W / 1-bit black and white. This setting uses only two colors: black and white. It is useful for drawings, cartoons, logos, and occasionally for images of text.

Choose the smallest appropriate color setting for your needs.

What resolution should this image be?

The resolution of your image will depend on the use you plan to make of it:

• 72 dpi / 75 dpi. Most computer monitors and projectors have a resolution of no more than 72 dpi. Therefore, images intended only for the web or for PowerPoint presentations need not have a resolution larger than this.
• 150 dpi. This is the default resolution setting in many scanning programs at UVa. It is double the normal screen resolution, which will enable you to enlarge a digital image to twice its physical size without pixelation.
• 300 dpi. If you need a high-quality printout of an image, or if an image is destined to be printed in a newspaper or journal, it will need to be scanned with a resolution of at least 300 dpi. Laser printers need this much information to print accurately.
• 400+ dpi. If you need to enlarge a postage stamp to the size of a poster, then you will need to scan at a high resolution. An image scanned at 450 dpi can be enlarged to 6 times its original physical size and displayed on a screen without pixelation.

Choose the smallest appropriate resolution for your needs.

Note that it is not wise to change an image's resolution after you have scanned it, though it is possible to do so in programs such as Photoshop. Once you have decreased an image's resolution, the color information acquired in the initial scan is lost forever. If you increase an image's resolution after it has been scanned, the program will fabricate color information.

Once the scanner settings are configured properly, click on "Preview" (or "Scan," or the equivalent). The scanner will begin its initial scan of its entire flatbed area; you will see and hear it begin.

When the preview scan of the entire flatbed area has completed, draw a box around all or part of your image using the mouse. Depress and hold the left mouse button, then drag the cursor across the preview image to select the area for final scanning. Only the area inside the box (the marquee) will be scanned.

Click "Final Scan," "Return to Photoshop," or the equivalent in order to begin the final scan.

When the scanning software has finished making the final scan of the image, it will automatically shut down and display the image in Photoshop. At this point, there are two common "fixes" that you might wish to make.

Rotating a skewed image

To rotate an image in Photoshop, go to Image --> Rotate Canvas. There you will see the following options:

• 180 degrees
• 90 degrees CW (clockwise)
• 90 degrees CCW (counter-clockwise)
• Arbitrary

Many images will need to be straightened slightly. Choose "Arbitrary" to enter a custom degree of rotation—such as 10 degrees clockwise or 0.5 degrees counter-clockwise.

Cropping an image

To trim unwanted material from an image, select the marquee tool (the box-drawing tool selected in the image) from the Photoshop toolbox, then drag your cursor across the image. Draw a box around those portions of the image you wish to keep, then choose Image  Crop. Only the selection inside the box will be retained.

The final step in scanning is to save your image as a file, and at this step, one last decision must be made: which file format to use.

Choose File  Save (or Save As) and click on the down arrow by the "Save As Type" box to see the list of file formats.

Which file format should this image be saved in?

There are many different image-specific file formats. Some of them are proprietary (i.e., the files are associated with one particular program), such as PSD (Photoshop Document). The most common non-proprietary file formats are these:

• .TIF – This format is lossless , which means that it is uncompressed: all information acquired in the initial scan is retained. Save high-resolution image files in this format if you plan to print them, archive them, or enlarge details from them. Files saved in this format are of extremely large size, however, and they cannot function well (if at all) on the web, in PowerPoint, or in word-processing programs.
• .PNG – Another common lossless format.
• .JPG – By far the most common format for images on the web. This format is lossy; when files are saved in this format, information that is judged to be redundant is discarded. Files in this format are of manageable size, however, and they look as good to the naked eye as uncompressed TIF or PNG files.
• .GIF – This format is used for simple 1-bit or 8-bit image files such as icons, JPG previews, drawings, cartoons, and logos. The files are very small.

Choose the smallest appropriate file format for your needs. This will usually be JPG. 

Give your file a name and save it to a folder where you will be able to find it again. Most public computers have folders dedicated to user data: on ITC lab computers, for instance, this folder is C:\LocalData; on the computers in the Electronic Text Center, this folder is C:\data. There are usually shortcuts to these folders on the Desktop.

Transferring Your Scanned Image

Once you have saved your file, you will need to move it to your personal or office computer. There are several methods of doing this:

Floppy disk. Most public computers at UVa no longer have floppy disk drives, because floppy disks do not hold much information and deteriorate after being stored for only 2 to 5 years. A floppy disk holds less than 2 megabytes of information.

Zip disk. Zip disks are more expensive than floppy disks, but they hold either 100 or 250 megabytes of information.Virtually all computers at UVa have Zip drives.

CD-Rom. Writable CDs are inexpensive, but not all computers at UVa have CD-writing ("burning") capabilities. A CD can hold 600 to 800 megabytes.

E-mail. You can e-mail an image file to yourself as an attachment using Mulberry, Simeon, or WebMail (http://www.mail.virginia.edu). But beware of sending files larger than 1 megabyte (1,000 kilobytes) through e-mail, since e-mail servers and programs are not designed to handle files this large.

Home Directory. For more information on using the convenient Home Directory file storage and web site service, see http://www.itc.virginia.edu/homedir.

Secure FX / WS-FTP. Ask a lab consultant how to use these programs.

See also the pages on this site concerning Making and Keeping and Transferring Files.