Trimap-Based Alpha Estimation

Implement a Trimap-Based Alpha Estimation algorithm to estimate the alpha matte from a given trimap, which divides an image into definite foreground, definite background, and unknown regions. The goal is to estimate the alpha values in the unknown region using color statistics.

The trimap is a mask that categorizes each pixel into one of three categories: definite foreground ($\alpha=1$), definite background ($\alpha=0$), and unknown ($\alpha$ to be estimated). This problem is a fundamental challenge in Image Matting, a technique used to separate the foreground from the background in an image.

1. Identify the definite foreground and background regions from the trimap.
2. Compute the color statistics, such as the mean color, for the foreground and background regions.
3. Estimate the alpha value for each pixel in the unknown region using the computed color statistics.

This technique is widely used in image and video editing applications.