Thank you for your suggestions.
Using g.fillRect() is not an option because I want to use more complex shapes too.
Making the path slightly bigger does not help. Even when the path overlaps the image border the last pixel of the image has the reduced alpha value.
Sorry for cross linking to another post in this forum. But this question
has a big impact on finding a solution for my current problem.
Could you be so kind to give me a short answer on this. It would really help me to find a solution.