Imaging Glossary

This is a glossary of common terms used in imaging. If you need more assistance please contact us and we will help describe it to you.

ADF: Automatic Document Feeder. A device that holds pages and feeds them one after another into a scanner.

Annotation: Graphics or text which is added to an image page that was not part of the original image.

ASCII: American Standard Code for Information Interchange (ASCII) is an ANSI binary-coding scheme consisting of 128 seven-bit patterns for printable characters and control of equipment functions. ASCII is the basis for information exchange between many computer systems.

Bitmap: A matrix of pixels representing an image. Each pixel location has a unique memory location in the computer, allowing efficient localized image processing.

Bitmap/BMP: A Bitmap image is a representation of a graphic image, displayed by setting individual pixels to white, black, or a color. this type of image is typically used by the Windows Paintbrush applet and has a filename extension of .BMP.

Black-and-White(Bi-Level, Bitogonal, Bitonal): The Black-and-White image type displays one bit of data per pixel on the screen as either black or white.

CCITT Group 3: Data compressed in one dimension yielding on average data reduction of about 5:1 or 6:1. The most common implementation of CCITT Group 3 is the data reduction circuit found in FAX machines. This technique is also known as “run length encoding.”

CCITT Group 4: Compression in two dimensions yielding and average data reduction of 25:1 or better. CCITT Group 4 compression requires the execution of 80-million bit oriented operations. The resulting compressed file is roughly the same size as a vector file consisting of graphics.

Compression: Compression is the process by which image data is reduced to require less storage space. The higher the compression, the lower the disk space requirement; the higher the resolution, the greater the image quality.

Crop: To select an area of an image and discard the unselected part.

Despeckle: Advaced capability of OCR that removes dots and speckles that commonly show up in faxed documents.

Deskew: Advanced capability of OCR that straightens an image that was scanned (or faxed) at an angle.

DPI: Dots per inch. A measurement of scanner resolution. The number of pixels a scanner can physically distinguish in each vertical and horizontal inch of an original image. Documents are normally scanned at a resolution of between 200 dpi and 400 dpi.

Duplex: The ability of a scanner to scan both sides of a sheet simultaneously.

Flatbed: A scanner design in which the document is placed in the scanner’s bed, either manually or by an automatic document feeder, and remains stationary during scanning. As a result, flatbed scanners provide a more stable target that other scanner designs, but they are generally slower.

GIF: The GIF (Graphics Interchange Format) file type was made popular by CompuServe and continues to be used by many graphic programs.

Gray Scale: There are two types of gray-scale images: Gray4 and Gray8. A Gray4 image uses 4 bits of data per pixel. Every pixel on the screen can be displayed in 16 shades of gray, giving the image much better clarity than black and white images. A Gray8 image uses 8 bits of data per pixel. Every pixel can be displayed with 256 shades of gray, producing better image clarity than Gray4. Gray8 images are particularly effective for storing pictures and photographs.

HTML: Hypertext markup language, used to describe World Wide Web documents and to provide links to other documents or hypertext.

Hyperlink: Annotation that produces a hot spot on an image page. When the hot spot is selected user’s view will move to another location. Imaging for Windows Professional Edition’s hyperlink annotation includes: movement to another page in the same image document, movement to another image document, or movement to an Internet address (URL).

Image: An image is a photograph, line drawing, or text document that has been converted to digitized form, usually by a scanning device. A scanned image is saved in a particular image format. Typically, an image is displayed in a window that can be sized or moved. Images can also be annotate, e-mailed, faxed, or printed.

ISIS: ISIS is a Scanner Interface developed by Pixel Translations. It was developed originally for SCSI-based scanners to be used with an Adaptec SCSI card.

JPEG: The Joint Photographics Experts Group compression type is used to compress 24-bit color (RGB24) and 8-bit gray-scale (Gray8) image files. JPEG produces a high compression ratio, but some image data is actually lost during compression.

Microfiche: Usually a 4″x 6″ sheet of film containing optically reduced images in a grid-like pattern, with a title section that can be read without magnification.

Microfilm: A film strip or roll of film, 16mm or 35mm, containing sequentially ordered documents that have been optically reduced to fit the film.

Optical Character Recognition (OCR): Optical character recognition (OCR) is the process of conversion of an unsearchable, image-based form of text into a searchable, character-based form. OCR can be performed on either machine printed or handwritten characters, or sometimes, on intermixed machine printed and handwritten.

PDF: Adobe Portable Document Format (PDF) is the de facto standard for electronic distribution of documents because it’s the best way to keep the look and feel you created intact. PDF files are compact, cross platform and can be viewed by anyone with a free Acrobat Reader.

Pixel: Short for picture element – describes a single element of a display or image on a computer. The Pixel is the basic building block of all images. In bitonal images, 1-to-256 possible values of gray (for and 8-bit scale image).

Portrait Orientation: An image registered so that it is taller that it is wide, with the narrow edge running along top and bottom.

PPM: Pages per minute. A measurement of the throughput speed of a scanner – how many letter-size pages the scanner can scan in one minute.

Resolution: Indicates the number of dots, often measured in dpi, that make up an image on a screen or printer. The larger the number of dots, and thus the higher the resolution, the finer and smoother images can appear when displayed at a given size. Low resolution caused jagged characters. The ideal resolution is a trade-off between quality and the overhead in storage power and processing strength required to use it.

Scale-to-gray: A technique for improved viewing quality of an image when it is scaled to view smaller that 100 percent. When viewing binary images (black & white) on a color or grayscale monitor, it is possible to substitute shades of gray as a quality of the image by maintaining more information on the screen than would be there if the pixels were simply removed. the quality of the scale-to-gray algorithm used directly effects the viewing quality of the image. Scale-to-gray has no effect on the quality of the original image.

Scaling: An operation that changes the dimensions of a drawing by an operator entered multiplication factor. This operation can be performed in one or more directions. A mechanism for re-sizing part or all of an image.

Scanner Interface: Software which provides interface between the scanner hardware and the application that initiates a scan process. It is made necessary by the wide variety scanner available on the market today.

SCSI: Small Computer System Interface. Pronounced “scuzzy”. An industry standard (of sorts) for connecting peripheral devices and their controllers to a microprocessor. SCSI defines both hardware and software standards for communication between a host computer and peripheral. Computers and peripheral devices designed to meet SCSI specifications should work together.

Skew: Misalignment of pages usually the result of poor page feeding in a fax machine or scanner.

Simplex: A document scanner that copies single-sided documents.

Speckle: The small dots and miscellaneous marks that show up on image pages that were not on the original. Most often the result of telephone line noise that occurs during a fax transmission.

Sticky Notes: Annotation that places text in a separate note (often yellow) that is then placed on the image page.

Thumbnail: Small representation of an image page. Properly constructed, thumbnails graphically represent the content and layout of the image represented. Good thumbnails help the user find a specific page in a document for viewing.

TIFF: The file format for Tag Image File Format (TIFF) images. TIFF supports multi-page black-and-white, gray-scale, and color images; several compression types; and a variety of options. TIFF is compatible with all image densities.

TWAIN: TWAIN is an open public scanning interface developed by a coalition of imaging hardware and software manufacturers. TWAIN defines the way in which a scanner, or other image acquisition device, communicates with the application program. With TWAIN, an application program can acquire images through any device that complies with its specification (for example, a scanner or camera). It is the standard for low-end scanners and comes in 16 and 32 bit versions.

Zoning, Automatic: OCR feature that automatically preselects text and graphics areas of the document prior to OCR. This is one of the more complex operations associated with OCR. If the quality of the resulting OCR is poor, particularly the document reconstruction, the user may wish to perform manual zoning.

Zoning, Manual: OCR feature that allows the user to reselect text and graphics areas of document prior to OCR. This helps improve OCR quality and accuracy as well as the quality of document reconstruction.

Zoom: The process of magnifying of the display of an image in a window to more closely inspect areas of a drawing.