I have a couple of solutions for that:
- remove the background of the saved preview
- do not change the image size and the project size
- do not move the vector layer that receives the image texture, but rather put it in a parent layer and move that layer instead
- paint in your paint program on a new layer, on top of the imported image layer
- paint outside the lines in your paint program (see below)
- fill solid colors with vector fillings in Anime Studio, rather than in your paint program
- if your design allows it, use thick outlines on your vector drawing
Here was the file I exported from Anime Studio Pro (vector drawing). I had to remove the background from the saved preview file with an image editor.
Here was the file I created with Artrage 2.5. Notice the colors are applied outside the lines, to ensure there will be no matching errors:
Both images are 640 x 480 pixels. I that is your project size, you should keep it at that size. If you start to change the width : height ratio, there will be matching error (meaning that the texture filling will not line up with the vector image).
Here is the resulting animation (not very good, but it demonstrates the technique):
Here is the project folder:
character.zip
The face is solid vector color, and the hair and shirt are texture fillings. As you can see, there are still some minor errors, which, I suppose, you could remove in post-production. It is still a crude technique, which can't be used for pixel precision, unfortunately. I could redo the image, and paint some more just above the left shoulder, so the white pixels don't show up.
As always, making it perfect requires several iterations.