About offset and blending width or height
Offset is used to clip the image. The larger the offset value, the more the image is masked (by black bar) at the corresponding side. E.g. Top offset of 100 will blank the top 100 lines.
Height or width is used to create a blending zone with a smooth brightness drop off. This is used to compensate for the double brightness in overlap areas. The value is the size of the blended area in pixels.


