Compositing
Foreground

Sometimes it is nice to have a foreground in front of the animation, like a curtain or a picture frame.
You need to use a picture which includes opacity (or ‘alpha channel’) information to act as a foreground. PNG and TIFF are two image formats which can include opacity data.
By clicking “Source”, you can select a source folder that will be scanned for images. Now you need only to select an image from the image browser and click to apply it to your animation. If you want to use video elements, be sure that they also contain opacity data.
To remove the foreground, just click .
As the intended use for iStopMotion in creating stop motion clips and not editing film material, only one foreground can be used per project.
Background

“Background” contains one of the special features of iStopMotion: Chroma keying
To add a background, you first need to set a background image or movie. Click “Source” and select a folder containing your background footage. Then you can select them from the image browser. After selecting one, click , activate Chroma keying and select the background element. iStopMotion will now try to detect the background color automatically. It searches for the most common color in the current preview. This means it would be helpful to use a uniform background with a color that isn't present on the target objects.
In the case that the doesn't work as you wish, you have further possibilities to adjust it.
By clicking “Pick color”, the mouse pointer changes to an eyedropper with which you can select the color from the image.
By clicking the action button (with the gear icon), you can access “Advanced Settings” and “Autodetect Color”.
The chroma keying settings are only applied to the frames recorded after setting the chroma key.
There is no single solution good for all situations, but in most cases the results of the autodetection are suitable with an appropriate background.
As the intended use for iStopMotion in creating stop motion clips and not editing film material, only one backround can be used per project.