I know how to rotate with a transform strip, but I need to rotate around an arbitrary point that is not in the center of the image.
It is possible friend, just follow these steps
import your image file in Blender VSE
click image offset
- Another step should be adding your transform strip to it but this is the place where you go wrong so before adding transform strip change these values by the formula -
x dimension = (video dimension x - file dimension x)/2
y dimension = (video dimension y - file dimension y)/2
so here my video dimensions are - (1920,1080)
and my image dimension are - (620,387)
to x = (1920-620)/2 = 650 Y = (1080-387)/2 = 347
so what we did here is all because to put the pivot point of image file in center.
now add your transform strip and rotate
Now it will rotate from center you can change the x and Y points of your transform strip to position your image anywhere but do not change the X Y points of original file .....Use transform strip only to position and rotation.
Could you not combine Position: and Rotation: to get the desired effect? I see that you are using the Transform strip, so a rotation such as this is possible. Note how it appears as if it is being rotated around the bottom left corner:
I did this by using the Transform strip with these settings:
To determine these settings, I first rotated it to the desired angle. I then moved it so that the left bottom corner was in the original spot; so that it looked like a rotation.
Alternately, you could jump out of the VSE to get a more accurate effect.
In the 3D Viewport, load your image onto a plane as shown here. Also align the camera as displayed. Next, from camera view, left click on the plane to bring the 3D Cursor to the point on the plane that you want to rotate around. With the plane selected, key Shift + Ctrl + Alt + C (yes, really) and select Origin to 3D Cursor:
Lastly, key R and Z to rotate your image around the point on just the right axis.
I did a couple of tests with but it doesn't like that is possible. This could maybe be done by editing the curves in the graph editor (which I tried). You could render an animation with the image being shadeless and the background being transparent. There might be a way to do it. Hope I was helpful.