Along with a scanner, you may want to capture images with a video camera. The camera focuses on the image and then transfers that image to the PC through a special interface board that converts the analog video signal to a digital format. This digitizer simplifies the image by combining palette values and setting the resolution. It also converts the digitized image into a standard graphics format such as TGA or PICT, which can be easily converted by the MDK's Convert tool. This setup lets you grab images with the video camera that can be read and enhanced by software the same as a scanned image.
Many different types of cameras exist and they can deliver images in many different formats (such as direct video, composite video, and National Television Standards Committee (NTSC)). After you've captured the image, you still must convert and enhance the image for incorporation within your application. The following paragraphs summarize the steps involved in this process.
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A video camera usually digitizes images faster than a scanner, but it doesn't necessarily provide the best quality for the money. So, unless you're willing to get the best equipment, you might be better off buying a scanner for your basic image capturing.
A proper setup and lighting can cut hours of image processing time. Using a copy stand as it comes out of the box invites trouble because quite often the lights are set to light the center of the stand. Often, one strong light (say, 1000 watts about five feet from the picture), will give you the proper, even illumination levels. Sometimes it is quite effective to tack the image to the wall and shoot it using a tripod-mounted camera.
To digitize images, you must plug a digitizer board into your computer, install the digitizer software, and connect the camera to the PC through the board. You may also want an extra monitor for viewing the camera image and some test equipment to ensure the best quality. Make sure all video equipment used is properly calibrated for color accuracy and reproduction.
Digitizers only accept RGB input, so you'll need to ensure your VCR or camera can output RGB. If you are capturing an NTSC signal, you'll need to convert it to an RGB signal first by using a special NTSC decoder.
Use a video camera whenever possible as it provides a more stable and higher resolution signal than a VCR. The next best signal is usually a live feed from cable, broadcast TV, or videodisc. Use VCR images only as a last resort. They produce highly unstable signals and low resolution output (around 240 lines of resolution).
Focus the camera on the object(s) whose image you want captured. Use the video capture hardware and software to grab the image and store it to disk.
All frame grabbers tend to distort the image slightly due to motion. The frame grabbing software is designed to compensate for this to some degree, however, for best results use still or slow moving images. Avoid grabbing in pause as the image is the most unstable in pause mode.
If you are capturing an entire sequence of video frames for an animation sequence, you'll have to shrink the original frames to a size that can be played back at a particular rate by the hardware. The standard Multimedia PC can play back at approximately 10-15 frames per second, with a frame size of approximately 100 pixels by 150 pixels by 8 bits. Reducing the frame size is probably best done with the original videotape before digitizing since the entire sequence will then be a consistent size. Some video boards can shrink a full screen video source. Otherwise, you may need to hire technicians in a TV studio at a greater cost.
Your targeted aspect ratio is the VGA monitor at 640:480 (or 4:3). The resolution of your camera or video image is bound to be different so you'll want to be sure the capture software you use can convert and correct the aspect ratio.
You'll need to crop the image to size and perform any necessary color, edge, or contrast enhancements. Edit the image to clean up any problems introduced when captured. Use the greatest color or monochrome depth possible. For instance, when touching up a 24-bit color image, use a software package capable of handling 24-bit colors. The Windows with Multimedia tools only handle 8-bit color manipulation.
By scaling the image down to less than full screen, you won't notice the lower resolution of the original video image. If you capture multiple video frames for an animated sequence, you'll have to shrink the original frames to a size that can be played back at a particular rate by the hardware. Contact a television studio for details as this requires professional expertise.
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.