VARIATIONS ON A TIP—TIP:
If you place your vignetted image over a non-white background you will see the white square background (top left). To remove the white background, create two circles, a white circle the size of the bitmap, and a smaller black circle.
Blend the two circles to create a soft black circle shape (middle left). Create a 24-bit bitmap of the soft black circle (Arrange > Create Bitmap Copy). Select the colored bitmap, then open the
Bitmap Gallery, select the soft-edged black bitmap, and press the Trans button. The result is the image shown bottom left.
I used Daniel Will Harris's duplicate trick to increase the color intensity.
(Courtesy of Sean Sedwards)