I have a binary image that maintains some unwanted region (small white dot) and hole regions (in figure 1). My idea is that to fill the object after I will remove the unwanted region but I don't now exactly wich method can help me
For this image in particular? I believe it should be sufficient to threshold (to get a binary image with only the visible particles present), then perform area opening (remove all objects with an area smaller than a certain value). Then, depending on how the remaining object looks, perform morphological operations such as thickening (simply enlarge the object) and closing (to fill in holes).
there are many ways to achieve it.
1) use Morphological Transformations + Thresholding.
2) Aditionally you can use Contour-detection, so the largest contour-area is the object you want to fill.