In this paper, we present an intensity mapping algorithm for enhancement and segmentation of pancreatic ductal nuclei in pancreatic ductal cell images acquired from pancreatic fine needle aspiration specimens with Papanicolaou stain. The upper envelope surface is obtained by rolling a ball of fixed size on the image surface followed by a moving average filtering to smooth out the downward spikes. When the upper envelope surface is mapped to the uniform intensity of the maximum intensity of the original image, the contrasts inside nuclei are magnified and the difference between intensities in the cytoplasm regions and the void background is compressed, resulting in improved separation of the nuclei from the rest. Results of enhancement and segmentation of pancreatic nucleus images are provided and compared to those without envelope mapping.