lv_vfw.zip_Capture_LabVIEW webcam_labview image_webcam_webcam la

- Video for Windows frame capture driver for LabView 4.0. - Snappy frame capture driver for LabView 4.0 and Snappy 2.0. by Eric Eilebrecht (eilebrec@colorado.edu) ---------------------------------------------------------------------- NOTE: When unzipping these files, make sure you set your "unzip" program to preserve the directory structure. Otherwise you'll have a bunch of source files in your main directory. Also, make sure you use an "unzip" program that preserves long filenames. I recommend the "Info-zip" suite of ZIP file programs - they will do both of these things by default. ---------------------------------------------------------------------- This is a basic hacked-together driver for LabView that allows single frames of video to be captured from any Video For Windows (VFW) video capture device, or Snappy framegrabber. I personally have used the VFW vi's with both the VideoLogic Captivator card and the Connectix QuickCam. The Snappy vi's require Snapy 2.0 software. Examples of how to use these drivers are in "vfw example.vi" and "snappy example.vi" Thie displays a preview window, captures a single frame, and displays it on screen. For best results, make sure your video mode is set to 16-bit color or better. To use the example, start by executing the VI. This will display a preview window, with some menu options. Play around with the options, then go back to the VI and press the "Snap!" button. You should then see the captured frame on the VI's panel. There are four values across the bottom of the screen. Try adjusting them to see what their effects on the captured frame are. These are the parameters to the frame capture routine. They work as follows: rWeight, gWeight, and bWeight are all all weighting values for the R, G, and B components of the image. They only have meaning relative to each other. Values of (1, 1, 1) give you an evenly weighted greyscale image. (1, 0, 0) gives you just the red component. (1, .5, .5) weights red twice as heavily as green or blue, and so on. allWeight is the maximum possible value that can be present in the final image array. Pixel values will be scaled between 0 and allWeight. Here's the basic idea of how to use this library: 1) Create a capture window using "Create Capture Window.vi" or "Create Snappy Window.vi" This will return a "window handle," which will be used by the other VI's. These take one parameter, which is a boolean. Set this to "true" if you want to see a preview window, or "false" if you don't. 2) When the camera is pointed at the thing you want to capture, execute one of the "Capture*.vi" vi's. The differences between these are in whether or not they save the image to disk. For the Snappy, you must use "Snap From Snappy.vi." 3) If you used "Capture to Temporary File.vi" or "Capture Frame.vi" in the previous step, then call "Get Frame Data.vi" to get a 2-D array of all of the pixel values that were just captured. This is where you specify the weightings discussed above. If you used a different vi above, then you already have the image data. Step 3 may be repeated many times for the same frame. This is useful if you want to get the same image with different color weightings. Step 2 may also be repeated if you want to capture more than one frame durring the execution of your VI. 4) When you are all done, destroy the capture window with "Destroy Capture Window.vi" or "Destroy Snappy Window.vi." BUGS: If you stop your VI before destroying the capture window, you may have trouble creating another one. The only way I know of to make it work again is to reboot. :( With some old 16-bit VFW drivers (like the VideoLogic Captivator), you will get a blank capture window every other time the window is created. You may be able to fix this by re-selecting the capture driver from the "Device" menu of the capture window. If you have any problem that you can't figure out, send me email (eilebrec@colorado.edu)