Classic Computer Magazine Archive CREATIVE COMPUTING VOL. 11, NO. 7 / JULY 1985 / PAGE 70

Choosing an image processor; which is right for you? (evaluation) Owen W. Linzmayer.

Choosing An Image Processor


Recently adapted from Digital Vision's Apple II model, ComputerEyes for the Commodore 64 is an inexpensive slow-scan device that plugs into the user I/O port on the back of the computer. Physically, the C64 ComputerEyes is a small 3 X 4 X 1-5/8 box very similar to its Apple cousin (see review in "Apple Cart,' October 1984) and is supplied with an Executive software program that handles all of the image acquisition routines. A high-contrast image is scanned in less than six seconds, and realistic grey scale images can be captured using a unique multi-scan process in which the threshold level is automatically increased with each scan. Eightlevel grey scale images may take up to 50 seconds to acquire. ComputerEyes is a video acquisition system, not a digital image processor. The Executive program serves to obtain an image and subsequently store it to disk--it does not have sophisticated image processing routines such as noise reduction or edge detection. The user must develop his own software if his needs are not met by the Executive program.

Fortunately, the software is not copy-protected. Digital Vision is now offering, at additional expense, software packages for both the C64 and Apple that allow the user to transform any standard hi-res image into a graphic that is compatible with Broderbund's bestselling Print Shop, so custom images can be used in greeting cards and posters.


Originally developed in England by Laurence Payne, the Diplomat digitizer is available in two models: one for the Apple II + and a more expensive IIe version that includes 64K Extended 80-Column Card facilities. The Apple IIe card occupies the auxiliary slot and fully supports double hi-res graphics. The Apple II + model may reside in any slot. Both versions are compatible with DOS 3.3, Pascal, and CP/M. The Diplomat differs from most other Apple units in that it can digitize continuously in real time at 60 frames per second, meaning that the subject need not be completely still. A video switch and cable are provided so that you can select "raw' video or digitized images, thus making it easy to fine tune the system on the fly. Moreover, all features of the digitizer can be controlled from the keyboard, and the video thresholds can be set by means of game controllers. The resolution of the Apple II + version is limited to the standard 280 X 192 pixel hi-res screen. However, in addition to double hi-res capabilities, the IIe unit features "quad' hi-res: 560 X 384 pixels. This is achieved by digitizing alternate video frames into double hi-res pages 1 and 2 using different thresholds computed from those set by the user. This mode provides nine simulated grey scales by rapidly switching the display between the double hi-res pages 30 times per second, yielding a picture that flickers slightly on most monitors with low persistence phosphor. The Diplomat is available with sophisticated digital image processing software in DOS 3.3 format or ROM firmware and is supported by a company newsletter. The Diplomat requires a closed circuit television camera with external synchronization like the Panasonic WV 1500 series and can be used with video tape recorders that have freeze frame capabilities.

DS-88 Digisector

Like all of the other digitizers for the IBM-PC, the DS-88 Digisector from Micro Works is an internal board that accepts interlaced RS-170 as well as broadcast NTSC signals. Micro Works was the first company to market digitizers and has been in business since 1977. The DS-88 version of the Digisector provides 512 X 512 pixel scans and yields a maximum of 256 grey scales. A typical 256 X 256 scan takes only four seconds to complete. For set-up and monitoring purposes, the DS-88 produces output comprised of the camera's raw video signal with a superimposed cursor which shows exactly where the Digisector is looking. The DS-88 comes with a menu-driven program called P-See that provides a variety of picture taking and image processing functions. User-definable color palettes allow assignment of up to 16 colors to different grey scale values for emphasis of desired shades with a color monitor. The P-See software requires a PC or XT with 192K, and an IBM color graphics card. The manual supplied with the DS-88 is short and to the point. It contains few diagrams, yet has detailed technical explanations of how the Digisector operates, including two schematics.


The Scion FAX640 is a single card that digitizes one frame of a monochrome RS-170 video image to a 16-level grey scale 640 X 408 or 544 X 480 pixel resolution image--all in 1/30 of a second. Because the image memory and all refresh logic are completely contained on the board, the FAX640 occupies no host memory and can maintain the grabbed image indefinitely. The digitized image can then be transferred in full or in part over the IBM PC data bus to Scion's PC640 for storage, modification, or display. Transfer of the full image takes about a second.

Graphicom Video Digitizer

The Graphicom Video Digitizer is designed to be fully compatible with Cheshire Cat's popular Graphicom graphics program for the TRS-80 Color Computer. The digitizer plugs into the CoCo via a multi-pak cartridge slot extender or a "Y' cable (available for $19.95). Images are digitized at close to real time, allowing you to take a snapshot of a video frame from any RS-170 video source simply by pressing the fire button on the joystick. External controls include horizontal and vertical position, horizontal width, image brightness and contrast. The Graphicom Video Digitizer requires a 64K CoCo with two joysticks and at least one disk drive. Printers supported include Epson, C. Itoh, Gemini-10, Okidata, and Tandy.

Image Capture and Video Display Adaptor

Imaging technology has taken a giant step forward with the recent introduction of the Image Capture and Video Display Adaptor boards from AT&T. These boards fit IBM PC, AT&T, and compatible computers, affording them the ability to store, retrieve, and manipulate color images of very nearly photographic quality.

The AT&T Image Capture Board (ICB) is an ultra hi-res frame grabber and buffer. It enables a microcomputer to digitize television-quality images from a standard composite source (such as a video camera) and to display these images on an analog RGB or NTSC composite monitor. The number of available colors is staggering: up to 32,768 can be displayed simultaneously.

Image capture is accomplished in a sixtieth of a second, and so can use a fullmotion video source as well as stills. Resolution is 256 X 256 pixels. The ICB is accompanied by driver and utility software under MS-DOS.

The AT&T Video Display Adaptor (VDA) can display digitized images at the same resolution, with up to 256 simultaneous colors from a palette of over 32,000. The capability to display subtile shading and color transitions gives VDA images a clarity and realism previously obtainable only with complicated systems costing many thousands of dollars.

The high-speed system also allows for graphic manipulation of images without the need for massive amounts of memory. Pictures can be transmitted via modem, and an image can be transmitted at 1200 baud in as little as 15 seconds.

VDA software includes image compression, bit area manipulation, and overlay graphics routines, including geometric shapes and three fonts.--JJA


Coming from the folks who brought touch tablets to the masses, MacVision from Koala Technologies has been the focus of a lot of attention lately, and rightly so. MacVision is a small, slick box the size of an external 5.25 drive for the Apple II. It was one of the first Mac digitizers to market and has become a favorite among Mac enthusiasts. MacVision also requires the use of one of the Mac's RS-442 serial ports.

The software works as a desktop accessory. Thus, it can be installed on any application disk and used at will given sufficient memory. A small window scan takes approximately five seconds, and scanning the entire Mac video screen requires 22 seconds. The resulting image can be stored in MacPaint format for enhancement.

MacVision images are displayed on the Mac screen at the maximum resolution offered: 320 X 240. Each pixel is digitized at 8 bits per pixel. The MacVision software is eloquent--a fine job of programming from Bill Atkinson, the author of MacPaint. Although MacVision does not offer extensive image processing capabilities, it does offer the best set-up routines.


Like all of the current Mac digitizers, the Magic digitizer is an external unit with a footprint slightly larger than a modem. RS-170 video is fed into a jack on the back of the box which is in turn connected to one of the Mac serial ports. The Magic must then be plugged into a wall outlet. Opening the camera icon on the desktop brings up a complex control panel from which you can scan, view images, adjust contrast and brightness, and change patterns. To get the most out of the software the user must maintain a working knowledge of this control panel from which all of the important functions of the system are accessed. For instance, the grey levels are reproduced in a variety of patterns ranging from all black to all white. The patterns in between can be edited by the user to bring out the best in delicate shading areas. And Magic saves its pictures as MacPaint documents as well. The Magic system produces images 768 X 480 pixels, but is limited by the Mac screen to display only 512 X 342 pixels--roughly 66% of the digitized image.

MicronEye Bullet

The MicronEye Bullet comes complete with hardware, software, user's guide, camera, and tripod. Images are saved as MacPaint files, and the software supports grey tone imaging capabilities through multiple scans.


The Micro-Imager is a large unit with a footprint rivaling that of the Mac itself. The system works like most of the others: RS-170 video into the box, digitizer in a serial port on the Mac. The Micro-Imager takes approximately five seconds to scan an image. Like the New Image Magic, the Micro-Imager also allows the user to define the graduated shaded patterns that represent a pseudo grey scale. The user can also select which of six patterns will be used to produce the overall picture. This is a thoughtful special effect and results in stunning images. Lines from both fields of the video frame are used to digitize individually every dot in a 512 X 322 dot image. For highcontrast images like line drawings, the two-shade mode is best. For portraits and such, the multi-shade (grey scale) mode is preferable. Contrast and brightness adjustments are made via knobs on the front control panel. Another hardware feature is an effective color rejection filter that removes virtually all chrominance (color) information from a color signal, yielding the highest quality b & w images.

Slightly less expensive than many of the other digitizers, the Micro-Imager offers good basic processing software, leaving the fancy stuff to designers of sophisticated graphics utilities.


Chorus Data Systems has introduced the newest member of the company's image processing family, the PC-Eye PC-1200. This high-resolution board is designed to produce up to 640 X 512 X 8-bit (256 levels of grey or color), approaching photograph quality on the computer monitor. The PC-Eye PC-1200 plugs into a full-length expansion slot in the IBM-PC, XT, AT and compatibles. Video images can be input through any of the four separate video input channels and are subsequently stored directly into PC main memory or graphics adapter memory. A 640 X 480 X 8-bit image can be captured in 0.6 seconds. Unique features include external trigger, NTSC color filter option, 4-bit digital input and output, and programmable gain and offset "trim.' Support is provided for graphics display adapter cards including IBM and compatibles, Hercules, and Tecmar. The GA-3 "revolution' card offers full display of 256 levels of grey or colors with 512 X 512 resolution. The GA-3 color pallette includes 16.7 million colors. An on-board graphics controller provides hardware speed for such functions as pan, zoom, and drawing.

PCvision Frame Grabber

PCvision Frame Grabber, a realtime video image acquisition and display module for the IBM PC and XT, includes a hardware module that plugs directly into an expansion slot in the IBM, comprehensive software driver routines, full user documentation, and all required interconnecting cables. The PCvision Frame Grabber digitizes images into 6-bit pixel data and stores them in an on-board 512 X 512 frame memory. Two additional bits enable two planes of graphic overlays, which can be used for generating and positioning text or graphics anywhere on the image without disturbing the stored video data. The unique architecture of the Frame Grabber enables it simultaneously to acquire and display 30 frames per second. Programmable look-up tables on the output signal allow arbitrary transformation of pixel intensity prior to display on an external monitor. The Frame Grabber can use its internal crystal to generate composite sync or horizontal and vertical syncs to drive the video source. Using three Frame Grabbers allows full-color image processing. In this configuration, one module is designated a master and generates the system timing for the other two modules. Each board digitizes, stores, and displays one primary color: red, green, or blue. NTSC composite color is, unfortunately, not supported.

PI-101 Photolmager

The PI-101 PhotoImager is actually an entire digital image processing system designed around a digitizer card initially introduced in late 1982. The PI-101 includes everything needed to digitize, display, communicate, and store hi-res grey scale and color photos. The PhotoImager consists of the PC-100 PhotoCaster digitizer/slow-scan television modem board; PV-100 PhotoViewer color graphics display board; a b & w RS-170 camera with lens, tripod and cables; four software disks; and two reference manuals. Images are digitized in eight seconds at a resolution of 128 X 128 pixels, with dithering of 16 levels of grey in the black and white mode and 4096 colors per pixel in the color mode. To achieve color digitization with a b & w camera, the PI-101 makes three successive scans, prompting the user to place a red, green, or blue filter in front of the lens before each scan. Although tedious, the result is a surprisingly realistic color image. When routed through the companion PhotoViewer color graphics board, images contain 320 X 200 pixel resolution on a true 16-level grey scale.

One very interesting feature of the PhotoCaster digitizer board is that it is equipped with a slow-scan television modem that can be connected to a radio transmitter and receiver to send and receive pictures. The PhotoCaster modem is compatible with most amateur SSTV equipment in use today. Additionally, the PhotoCaster can digitally transmit high quality photos over the telephone lines in one to four minutes. The PhotoViewer board also satisfies the proposed NAPLPS videotex/teletext protocol standards for resolution, color and grey scale.

Private Eye

Probably the most impressive feature of Private Eye is that it can capture moving video images, so the object being scanned does not have to remain still for the length of the scan. In fact, Private Eye can capture a complete video frame in real time (1/30 second) compared to conventional digitizers which require several full seconds. Each video frame is digitized into a 512 X 512 pixel image that may be viewed on the Mac with a movable window. As is standard with all Mac digitizers, the images can be saved as MacPaint files to insure compatibility with all graphics packages. According to the manufacturer, Private Eye uses a patent-pending "spray paint' random dot pattern generator, which provides images with near continuous shades of grey. Unlike the other Mac digitizers, Private Eye allows TV adjustments to be made when viewing the image on the Mac itself, rather than on an external monitor.


The ThunderScan unit is unique in that it does not accept RS-170 video input from any video source--it is a self-contained unit that replaces the ribbon cartridge inside the Imagewriter printer. True to its name, ThunderScan "scans' any document, drawing, or image that can be fed into the Imagewriter like paper. It shines a beam of light at precise spots on the paper, and a sensitive photosensor detects how much light is reflected and determines a grey scale value from 1 to 32 for that spot. Like the Koala software for the MacVision, the ThunderScan software was written by an Apple author. The man behind the keyboard this time was Mac team member and software priest, Andy Hertzfeld, author of the Switcher accessor. The ThunderScan software allows you to scan images of various sizes up to 8 X 10 with a 512K Mac. However, this process takes up to 20 minutes to complete--a rather long time, compared to the scant seconds it takes most video digitizers. But remember, this is optical digitization, and provides precise reproduction of flat documents since there is no need to bother with correct lighting and contrast levels. ThunderScan also lets the user enlarge or reduce the image before scanning. Image magnification is available from 25 to 400% of the original. Other useful adjustments are available after the image has been digitized. These include contrast, brightness, and pattern editing.

One major drawback of ThunderScan is that the scanning unit must be replaced by the printer ribbon each time a picture is printed. This blow can be softened by waiting to print a group of images at the end of an acquisition session. Images can be stored in MacPaint in ThunderScan format and selected by the user. Like all digital information, ThunderScan images use large amounts of internal memory and disk space.


The Vidx-1 video digitizer is a small box that plugs into the RS-232 serial port on the back of the TRS-80 Color Computer. Unlike the Computize unit, there is no need for Y-cables or multi-paks. In addition, the Vidx-1 digitizer is the only system that runs on the basic 16K cassette CoCo, as well as systems with additional memory and disk drives, including the Color Computer 2.

The Vidx-1 hardware has two knobs; one controls image contrast, the other, image width. The width knob controls the speed at which Vidx scans the RS-170 image and can horizontally stretch or compress the digitized image on the CoCo screen. It takes approximately four seconds to digitize an image, and the resulting picture can be saved to disk in either Graphicom or Radio Shack standard binary formats. Most users will want to get hardcopies of their images; the Vidx software supports printouts on the Prowriter 8510. Cost: $99.95 (Vidx-1), $124.95 (Vidx-2, includes a two-port RS-232 switcher).

Table: Digital Image Processors

Photo: Sample images. This page: above, Diplomat; left, Computer Eyes. Opposite page: top, Magic; bottom, MacVision.

Photo: ThunderScan sample image.

Products: ComputerEyes (computer apparatus)
Diplomat (computer apparatus)
DS-88 Digisector (computer apparatus)
FAC640 (computer apparatus)
Graphicam Video Digitizer (computer apparatus)
Image Capture and Video Display Adaptor (computer apparatus)
MacVision (computer apparatus)
MicroEye Bullet (computer apparatus)
Magic (computer apparatus)
Micro-Imager (computer apparatus)
PC-Eye (computer apparatus)
PCvision Frame Grabber (computer apparatus)
PI-101 Photolmager (computer apparatus)
Private Eye (computer apparatus)
Thunderware Thunderscan (Scanning device)
Vidx-1 (computer apparatus)