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Help pages about ImageGrab    
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Last update on Wednesday, September 15, 2010
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The intervalometer is a powerful feature of ImageGrab for extracting and saving images automatically at a given time interval, or if you prefer to extract a frame every x frames. To
display the intervalometer click on the button
When the intervalometer is visible, set the interval between two snapshots. You must indicate the time unit and the value. The time unit is either frames, seconds or minutes. I am sorry, you can only request an entire number of one unit, so you cannot request 3 minutes and 12 seconds. But of course, you get the same result in converting all to seconds, and setting 3x60+12=192 seconds.
The number of images to be saved with that interval and that given video duration is then displayed in purple at the right. Before launching the intervalometer, you must also choose between the Normal mode and the Precise Mode.
The Normal mode for the intervalometer is selected if the checkbox Precise is not checked. In that case, the intervalometer tries to advance directly to the position of the next image to be grabbed, until there is none left. The advantage of this mode is that it is fast. The drawback appears with some video types, in particular mpeg, where it is very difficult to advance to the next image if it is close to the current one. If you want to take snapshots at short intervals, like every frame, or for a frame every two frames, the image will sometimes remain still and you may grab the same image several times.
To avoid this issue, ImageGrab features the Precise mode. It is selected when the checkbox Precise is checked. In this mode, ImageGrab plays the whole video fully (but at maximum speed), and displays on the video screen every single image, so that it can surely grab those of interest. In this mode you should be able to grab even at intervals of one frame, that is to say extract every frame as an image file. The drawback is that this mode is slow and sometimes very slow because it must play the whole video file.
Start the intervalometer by clicking on its switch or by typing CTRL+I. If you want to break before it has stopped by itself at the end of the video, click again on the switch or type again CTRL+I. You may also type the Esc key.
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Help pages for ImageGrab: 
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Display the intervalometer
. Set
the time interva
.
Use Precise mode to grab images
separated by short intervals
. Start
and Stop the intervalomete
.
Display the intervalometer
or type ALT+J.
The navigation buttons are replaced with the intervalometer's
interface. 
. Set
the time interval
.
Use Precise mode to grab images separated by short intervals
.
Start and Stop the intervalometer