Fig. 3

Figure 3. Contiguous region extraction. (A) Binary thresholded image from Fig. 1 B. Solid rectangles mark irregular protrusions. Inset is a magnified view of the area marked by the dashed rectangle. A star marks the point for initiating region extraction. (B) Positions of two 3 × 3 pixel grids for the area within the solid rectangle in the inset of (A). Black was changed to gray for presentation. Double-headed arrow denotes the diagonal shift of grids (additional two grid shifts are not shown for clarity). Panels on the right show labeling each 3 × 3 window based on the intensity of pixels it contains. Checked windows (labeled “C”) are set to 255 intensity, and the sealed windows (labeled “S”) are filled with the background intensity (represented by semitransparent red or blue). (C) AND operation of the extracted foreground from two grid variations. Because red and blue represent the background, pixels where they overlap are set to 0, and pixels for which only one color is present are not changed. (D) Ventricle extraction using a 2 × 2 pixel window. The left panel is the filtered grayscale image used for ventricle extraction; stars mark the points for initiating ventricle extraction. The right panel shows the extracted ventricle (area filled in white) overlaid onto the original image for comparison.