武汉理工大学数字图像处理英文课件 Chapter1（4）.pptVIP

Binary Image Morphology 3x3 Structuring Element Hit or Miss Transformation Dilation Erosion Opening Closing Matlab function graythresh Example of graythresh top-hat and bot-hat Skeleton Thin Remove Thicken Pruning Matlab routine bwmorph * Morphological processes work much like spatial convolution in that pixel values are based on values of the neighboring pixels. Instead of constructing a dot product of a mask array and a pixel array, morphological processes use set theory operations such as intersection (AND), union (OR), and complement (NOT) to combine pixels logically into a resulting pixel value. The mask array in spatial convolution becomes the structuring element in morphology. The objective is to determine a value for the central pixel, shown below. For the 3 x 3 structuring element case, neighboring pixels are converted to a one-dimensional array using the following pattern. ?????????????????????????????????????????????????????????????????????????????????????????? This general implementation is called the hit or miss transform. When the mask values match their respective pixel values, we have a hit. Otherwise, it is a miss. A simplified example for the morphological process is B is the structuring element, often a 3 x 3 array of 1s (ones(3)). Dilation returns 0 if all nine pixels are 0 and 1 otherwise. dilated twice dilated once original se = strel(square,3); e1 = imdilate(in,se); new e1 = bwmorph(in,‘dilate); old B is the structuring element, often a 3 x 3 array of 1s (ones(3)). Erosion returns 1 if all nine pixels are 1 and 0 otherwise. eroded twice eroded once original A B se = strel(square,3); e1 = imerode(in,se); new e1 = bwmorph(in,erode); old Opening generally smoothes the contour of an image, breaks narrow passages, and eliminates narrow protrusions. opened original A?B = (A B) B Opening is the erosion of A by structuring element B followed by dilation by the same structuring element. opened original A?B = (A B)