The latest htpertext version of this guide will be available on http://jurgen.physics.utoronto.ca:8080/~tim/Cannibal.html
Introduction
QuickSnap is a shareware application designed to work with the Connectix QuickCam. It is an improvement over the QuickPICT application supplied with your QuickCam, as it allows you to save photographs in JPEG format. Additionally QuickSnap has an automatic exposure feature and a spot-meter which allows you to work efficiently in conditions where the light level is not constant.
Version 1.0 is a major improvement on previous versions. It now supports motion detection ! A quick setup guide for doing motion detection is included on another file.
Contact me with suggestions by email (tim@jurgen.physics.utoronto.ca) or preferably via my www site which will contain future updates and other special features ...
QuickSnap has two main windows, the Viewfinder window and the Info window. The Viewfinder is just that. It contains the current view of the camera. If you take a photo, then a window will appear containing the image which filled the viewfinder at that moment. You can choose to discard photos you take or you can save them in JPEG or RAW formats.
The info window floats around the desktop filled with useful info. It contains the currrent brightness averaged over the spot meter (see below). The current exposure time in milliseconds and the number of bytes per frame. Play with the compression settings (Video menu) and see how this number varies with different compressors. This is an upper limit on the size of images. The lossless algorithms like JPEG usually produce an image much smaller than this. This means that the actual image file sizes are far smaller that this value. I find that for QuickCam images that the final JPEG image is 5 times smaller than the maximum shown in the info window. Once a picture has been saved (thus invoking the compression routines), the info windw image size contains the size of the last saved image file (in bytes). If you resize the window than this field will return to the upper limit size. Please email me any suggestions on further info needed here.
_____________________________
Taking pictures with QuickSnap
To take a photo with QuickSnap, simply plug in your QuickCam and make sure the camera is operating correctly. A good way to verify this is to launch one of the applications supplied by Connectix (I suggest QuickPICT)) and verifying that it operates. Then quit QuickPICT and follow the following simple instructions...
• Run QuickSnap and you should see the object of interest (whatever the Camera is pointing at) in the Viewfinder window. Superimposed over the image is a rectangle. This is the spot meter used to control the exposure of the camera.
• Choose 'take photo' N from the File menu. A photo window will appear containing the image you have just taken.
• Choose 'save' or 'close' from the File menu. The photo will be saved in JPEG format and you will be prompted for the filename.
New Photo N
This takes a still image of what is in the viewfinder. This image is places in a window. If you wish to save this window, select the window and choose 'save' from the file menu. IF you choose 'close' from the file menu, the window is closed and if the contents are not saved then they are lost.
Copy Photo C
You can select a window, either the viewfinder of a photo window and copy it to the desk scrap. You may then paste this photo into other applications.
Exposure Control in the Viewfinder
In the Viewfinder Settings Dialog there are three parameters which can be set. The first is the desired brightness, specified in percent. One hundred percent means that the average value of the pixels in the spot meter is saturated (i.e., white/ slow exposure time) and zero percent means the pixels being black (fast exposure time). You probably will not want to change this value outside the range 40-60 %. QuickPhoto uses a simple algorithm to adjust the exposure time of the QuickCam in such a way as to make the brightness inside the spot meter (see below) is close to the desired brightness. The default value for this parameter is 50%.
The second parameter which can be set from the Photo Settings Dialog, is the exposure damping. This determines the speed of response of the automatic exposure to fluctuations in the ambient illumination. If you wish the camera to respond very quickly then this number should be larger (try 300) and if you think the light will be varying very slowly then a good idea is to reduce this value (try 50). Smaller values reduce the possibility of the brightness oscillating around the desired value.
The third option will let you switch on the time-stamp feature. This places the current time and date in the lower right of the picture. Great for time-lapse movies when you want to figure out when an event occurred.
Spot Meter
The spot meter is a rectangle that you define in the video window. This rectange defines the are over which the automatic exposure is controlled. For example if the rectange is a small square, then QuickSnap checks to contents of that square and adjusts the exposure so that the contents of that square have an average brightness equal to that specified in the exposure dialog.
The rectangle you define must be a multiple of eleven pixels high and wide. To precisely position this rectangle it is best to click on the top left corner first and then drag (holding the mouse button down) to the bottom right corner. Try doing it the other way to see why. This shouldnt be a problem unless your spt rectangle is miniscule. Something I don't recomment as then the brightness of the backgroun can appear to fluctuate dramatically as the light intensity varies inside the spot meter rectangle.
Add Comments
Choosing this menu option will pop up a dialog which allows you to add text comments to your JPEG files. This cute feature is useful as you can effectively add captions to your JPEG images. To use this you will have to register your program ! This can be done by sending in your shareware fee (preferably by email) and you will receive a code which, typed into the registration box, will customize QuickSnap and provide these features.
JPEG Quality & Shutter Settings (Photo Settings)
This Dialog allows one to change the settings for photo files. The first option is the "beep Before Photo" option. When this is enabled, the computer will beep repeatedly for two seconds before a photo is taken. This is great for those delayed exposure photo's (see next paragraph).
The second parameter which can be set from the Photo Settings Dialog, is the shutter delay. This is the number of seconds which QuickPhoto will wait (after the 'New Photo' command (Command-N) is issued) before taking the photo. The default setting here is zero, meaning that the photo is taken immediately.
The third option is the JPEG image quality. THis is a number between 1 and 100 which determines the quality of the saved JPEG image. Selecting a number less than 25 results in low quality but smaller picture files. Because the quickCam is currently restricted to 4 bit greyscale. I recomment using a quality of 5 (this is very low but the results are still pretty good). Experiment with this parameter and see what you find is best.
_____________________________
Making Time-lapse Movies
A time lapse movie is one where a single frame is taken at fixed time intervals, usually of more than a second. This means that when the movie is played back, the subject of the movie appears to speed up. So if you take one thousand frames at ten second intervals, then play them back at ten frames per second, time in the movie will appear to have sped up by a factor of one hundred. Clouds speed across the sky, flowers burst open in seconds instead of hours. This is a MUST DO feature of QuickSnap. Make Time lapse movies and impress your friends.
To make a time lapse movie with QuickSnap, simply plug in your QuickCam and make sure the camera is operating correctly. The exposure control is achieved using the Photo menu controls. Just like when you're taking still images.
Record Movie
This begins recording a movie. Your mac or powerbook will not be able to sleep during the taking of the movie. You will be prompted for a movie file name at this point.
Stop Recording
This halts the recording of the movie and closes the movie file.
Pause Recording
This halts the recording of the movie without closing the movie file. To resume recording you must choose the Record Movie Menu Item. This option is only available if you register your version of QuickSnap.
Add Single Frame
Adds a single frame to the current movie. If no movie has been opened then one will be opened and a single frame added. This option is only available if you register your version of QuickSnap.
Time Lapse Setup
This specifies the time interval in seconds between frames in the time lapse movie. This can be specified in fractions of a second. Note that the timing is not incredibly accurate due to hard disk accesses e.t.c. Notice that if this value is less than the time required to compress an image, QuickSnap will try as fast as it can to keep up. This means that it will digitize continuously.
Compression
The compression menu item (Video Menu) pops up a standard dialog which allows the user to set the compression type for time-lapse movies. The default is ANIMATION ('rle ') compression, this allows for fast decompression and with greyscale images gives a good compression ratio. If one chooses NONE for the compression then the output is a raw binary (4 bits per pixel) dump of the camera image. All the compression formats are supported. I suggest you stick to animation compression for small frame sizes (less than 240 x 180) and the CinePak (with a low quality rating) for larger frame sizes. CinePak does require about 5 seconds to compress one frame (on my Duo 250) so this will limit the maximum frame rate.
_____________________________
KNOWN BUGS & FEATURES TO COME
• Will allow the user to save the image in a QuickTime PICT 2 format.
• GIFF output is NOT coming ! Compuserv has started to require royalties from any applications which either read or write the GIFF format. Bummer huh.
• Scriptability will be added (when the project is converted to C++)
