Histograms and Matching 主講人：虞台文

Content Overview Basic Histogram Structure Accessing Histograms Basic Manipulations with Histograms Color Spaces Histogram Comparisons Back Projection

Histograms and Matching Overview

Histograms

Histogram of an Image

Histogram for Skin Color

Applications Object Detection Image Retrieval Gesture Recognition

Histograms and Matching Basic Histogram Structure

CvHistogram  Multidimensional Histograms typedef struct CvHistogram { int type; CvArr* bins; float thresh[CV_MAX_DIM][2];// for uniform histograms float** thresh2; // for nonuniform histograms CvMatND mat; // embedded matrix header // for array histograms } CvHistogram; typedef struct CvHistogram { int type; CvArr* bins; float thresh[CV_MAX_DIM][2];// for uniform histograms float** thresh2; // for nonuniform histograms CvMatND mat; // embedded matrix header // for array histograms } CvHistogram;

Create Histogram CvHistogram* cvCreateHist( int dims, int* sizes, int type, float** ranges = NULL, int uniform = 1 ); CvHistogram* cvCreateHist( int dims, int* sizes, int type, float** ranges = NULL, int uniform = 1 );

Defer Set Ranges Used when calling cvCreateHist with ranges = NULL.

Clear and Release Histogram

Histograms and Matching Accessing Histograms

Access Bin Data

Direct Access of Bin Data typedef struct CvHistogram { int type; CvArr* bins; float thresh[CV_MAX_DIM][2];// for uniform histograms float** thresh2; // for nonuniform histograms CvMatND mat; // embedded matrix header // for array histograms } CvHistogram; typedef struct CvHistogram { int type; CvArr* bins; float thresh[CV_MAX_DIM][2];// for uniform histograms float** thresh2;// for nonuniform histograms CvMatND mat;// embedded matrix header // for array histograms } CvHistogram; hist->mat.data.fl

Direct Access of Histogram Information typedef struct CvHistogram { int type; CvArr* bins; float thresh[CV_MAX_DIM][2];// for uniform histograms float** thresh2; // for nonuniform histograms CvMatND mat; // embedded matrix header // for array histograms } CvHistogram; typedef struct CvHistogram { int type; CvArr* bins; float thresh[CV_MAX_DIM][2];// for uniform histograms float** thresh2; // for nonuniform histograms CvMatND mat; // embedded matrix header // for array histograms } CvHistogram;

Histograms and Matching Basic Manipulations with Histograms

Calculate Histogram void cvCalcHist( IplImage** image, CvHistogram* hist, int accumulate=0, const CvArr* mask=NULL ); void cvCalcHist( IplImage** image, CvHistogram* hist, int accumulate=0, const CvArr* mask=NULL );

More Operations

Example  Graylevel Histogram

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Histograms and Matching Color Spaces

RGB Color Space

HSV Color Space

YCbCr Color Space

Color Space Conversion Article Some Algorithms Applet

OpenCV  Color Space Conversion void cvCvtColor( const CvArr* src, CvArr* dst, int code ) void cvCvtColor( const CvArr* src, CvArr* dst, int code )

Skin Color Detection by HSV and RGB

Automatic Face Detection

Histogram Usage Examples

Example  Hue-Sat Histogram

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Histograms and Matching Histogram Comparisons

Histogram Comparisons in OpenCV #define CV_COMP_CORREL 0 #define CV_COMP_CHISQR 1 #define CV_COMP_INTERSECT 2 #define CV_COMP_BHATTACHARYYA 3

Histogram Comparisons in OpenCV #define CV_COMP_CORREL 0 #define CV_COMP_CHISQR 1 #define CV_COMP_INTERSECT 2 #define CV_COMP_BHATTACHARYYA 3 Correlation Method (CV_COMP_CORREL) maximum mismatch perfect match

Histogram Comparisons in OpenCV #define CV_COMP_CORREL 0 #define CV_COMP_CHISQR 1 #define CV_COMP_INTERSECT 2 #define CV_COMP_BHATTACHARYYA 3 Chi-square Method (CV_COMP_CHISQR) bad mismatch perfect match

Histogram Comparisons in OpenCV #define CV_COMP_CORREL 0 #define CV_COMP_CHISQR 1 #define CV_COMP_INTERSECT 2 #define CV_COMP_BHATTACHARYYA 3 Intersection Method (CV_COMP_INTERSECT) total mismatch perfect match H 1 and H 2 are normalized to one before comparing

Histogram Comparisons in OpenCV #define CV_COMP_CORREL 0 #define CV_COMP_CHISQR 1 #define CV_COMP_INTERSECT 2 #define CV_COMP_BHATTACHARYYA 3 BHATTACHARYYA Method (CV_COMP_BHATTACHARYYA) total mismatch perfect match

Histogram Comparisons in OpenCV

Histograms and Matching Back Projection

Back projection is a way of recording how well the pixels or patches of pixels fit the distribution of pixels in a histogram model – cvCalcBackProject() – cvCalcBackProjectPatch()

Back Projection Back projection is a way of recording how well the pixels or patches of pixels fit the distribution of pixels in a histogram model – cvCalcBackProject() – cvCalcBackProjectPatch()

cvCalcBackProject

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Patch-Based Projection