image-processing - How to detect large galaxies using thresholding?

Question

I'm required to create a map of galaxies based on the following image,

http://www.nasa.gov/images/content/690958main_p1237a1.jpg

Basically I need to smooth the image first using a mean filter then apply thresholding to the image.

However, I'm also asked to detect only large galaxies in the image. So what should I adjust the smoothing mask or thresholding in order to achieve that goal?

Answer 1

两者：通过首先平滑图片，较小星系周围的像素将与黑色空间“混合”，从而转移到较低的强度值。然后可以对这种较低的强度进行阈值处理，只留下较大星系的白色中心。