1) The document discusses various techniques for image segmentation including histogram-based techniques, K-means clustering, fuzzy C-means clustering, and watershed segmentation.
2) Histogram-based techniques use the histogram of pixel intensities or colors to separate an image into regions but do not capture much detail. K-means and fuzzy C-means are clustering techniques that group similar pixels but do not consider spatial relationships.
3) The document surveys recent research on applying these techniques and combinations such as initializing fuzzy C-means with histograms to improve convergence speed and incorporating spatial data.