BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing a configuration of a face detection apparatus;
FIG. 2 is a flowchart showing an operation of the face detection apparatus;
FIG. 3 is a schematic view showing plural hierarchical images obtained through Step S2 of FIG. 2;
FIG. 4 is a flowchart showing a procedure of a process of generating four-direction edge feature images performed in Step S3 of FIG. 2;
FIGS. 5A to 5D are a schematic view showing an example of a differentiation filter corresponding to each of four directions of a horizontal edge, a vertical edge, an obliquely upper right edge, and an obliquely upper left edge;
FIG. 6 is a schematic view explaining a face detecting process of Step S4 of FIG. 2;
FIGS. 7A to 7D are schematic views showing four-direction edge feature images corresponding to a determination region in an input image;
FIG. 8 is a schematic view showing an example of contents of a weighting table;
FIG. 9 is a flowchart showing a procedure of the face detecting process performed to the determination region set in the input image;
FIG. 10 is a flowchart showing a procedure of a determination process performed in each determination step of FIG. 9;
FIG. 11 is a flowchart showing a modification of the face detecting process;
FIG. 12 is a graph showing a weighting table value (hereinafter referred to as table value) and a polynomial curve which approximates the table value of each pixel value of a feature pixel, when a certain pixel value of the feature pixel is set to a horizontal axis while a weight w is set to a vertical axis;
FIG. 13 is a schematic view showing an example of contents of a coefficient table;
FIG. 14 is a flowchart showing a procedure of determination process in the case of use of the coefficient table;
FIG. 15 is a graph showing a relationship (polygonal line A) between a detection ratio and a false detection ratio in the case of use of a coefficient table (polynomial) and a relationship (polygonal line B) between a detection ratio and a false detection ratio in the case of use of a weighting table;
FIG. 16 is a flowchart showing an operation of a face detection apparatus;
FIG. 17 is a schematic view showing two hierarchical images obtained through Step S52 of FIG. 16 and plural kinds of determination regions;
FIG. 18 is a flowchart showing a procedure of a face detecting process performed to three kinds of determination regions in an input image;
FIGS. 19A to 19D are schematic views showing examples of the input images in the case where a rotation angle of a detection-target face is changed;
FIG. 20 is a schematic view showing a correspondence between a feature point (feature pixel) assigned by a weighting table and a feature point on a face image in an upright state and a correspondence between the feature point (feature pixel) assigned by the weighting table and a feature point on a face image rotated by +90°;
FIG. 21 is a schematic view showing a relationship, between an xy coordinate of the feature point (feature pixel) assigned by the weighting table and an xy coordinate of feature points corresponding to −90°, +90°, and 180° face images (edge feature images);
FIGS. 22A to 22D are schematic views showing examples of the input images when the rotation angle of the detection-target face is changed;
FIG. 23 is a schematic view showing a correspondence between the feature point (feature pixel) assigned by the weighting table and the feature point on the face image in the upright state and a correspondence between the feature point (feature pixel) assigned by the weighting table and the feature point on the face image rotated by +45°;
FIG. 24 is a schematic view showing a relationship between the coordinate of the feature point assigned by the weighting table and the xy coordinate of the feature points corresponding to +45°, −45°, +135°, and −135° face images (edge feature images);
FIG. 25 is a schematic view showing two hierarchical images and a determination region used for each hierarchical image;
FIG. 26 is a flowchart showing the procedure of the face detecting process;
FIG. 27 is a schematic view showing two hierarchical images, a determination region, and a roughly-detecting determination region;
FIG. 28 is a schematic view conceptually explaining a method of generating a common weighting table;
FIG. 29 is a flowchart showing the procedure of the face detecting process performed to a hierarchical image;
FIG. 30 is a schematic view showing two hierarchical images, a determination region, and a roughly-detecting determination region;
FIG. 31 is a flowchart showing the procedure of the face detecting process;
FIG. 32 is a schematic view showing two hierarchical images, a determination region, and roughly-detecting determination region;
FIG. 33 is a flowchart showing the procedure of the face detecting process; and
FIG. 34 is a flowchart showing the procedure of the face detecting process.
Patent Application
20070201747
