Ring dilation and erosion techniques for digital image processing

A method for eroding an object within an image, wherein the image is represented using a plurality of image pixels, and wherein the object is represented using a plurality of object pixels that are a subset of the plurality of image pixels, the method comprising:

• specifying a boundary and an origin of a structuring element, wherein the boundary includes a plurality of boundary pixels;
• and
• for each image pixel,
• overlaying a copy of the structuring element onto the pixel such that the origin of the copy is adjacent the image pixel;
• comparing each boundary pixel with an adjacent ones of the image pixels;
• and
• selecting the image pixel if each of the boundary pixels overlaps an object pixel.

A method for grouping selected pixels within an image represented using a plurality of image pixels, wherein the selected pixels are a subset of the plurality of image pixels, the method comprising:

• specifying a first structuring-element having a first boundary and a first origin, wherein the first boundary includes a first plurality of structuring-element boundary pixels;
• overlaying the origin of a copy of the first structuring element onto each of the selected pixels such that the first boundaries of the copies intersect to form a dilated image feature having a first feature boundary;
• specifying a second structuring-element having a second boundary and a second origin, wherein the boundary includes a second plurality of boundary pixels;
• and
• for each image pixel within the first feature boundary,
• overlaying a copy of the structuring element onto the image pixel such that the second origin is adjacent the image pixel;
• comparing the second boundary pixel with an adjacent one of the image pixels;
• and
• selecting the image pixel if each of the second boundary pixels is adjacent an image pixel within the first feature boundary.