图像的颜色空间

#include "opencv_libs.h"
#include <highgui.h>
#include <cv.h>
#include <math.h>

/*
 * 描述：实现RGB颜色模型到HSI颜色模型之间的相互转换
 * 作者：qdsclove(qdsclove@gmail.com)
 * 时间：16:01 4/17 星期三 2013
 */

// 将HSI颜色空间的三个分量组合起来，便于显示
IplImage* catHSImage(CvMat* HSI_H, CvMat* HSI_S, CvMat* HSI_I)
{
    IplImage* HSI_Image = cvCreateImage( cvGetSize( HSI_H ), IPL_DEPTH_8U, 3 );

    for(int i = 0; i < HSI_Image->height; i++)
    {
        for(int j = 0; j < HSI_Image->width; j++)
        {
            double d = cvmGet( HSI_H, i, j );
            int b = (int)(d * 255/360);
            d = cvmGet( HSI_S, i, j );
            int g = (int)( d * 255 );
            d = cvmGet( HSI_I, i, j );
            int r = (int)( d * 255 );

            cvSet2D( HSI_Image, i, j, cvScalar( b, g, r ) );
        }
    }

    return HSI_Image;
}

// 将HSI颜色模型的数据转换为RGB颜色模型的图像
IplImage* HSI2RGBImage(CvMat* HSI_H, CvMat* HSI_S, CvMat* HSI_I)
{
    IplImage * RGB_Image = cvCreateImage(cvGetSize(HSI_H), IPL_DEPTH_8U, 3 );

    int iB, iG, iR;
    for(int i = 0; i < RGB_Image->height; i++)
    {
        for(int j = 0; j < RGB_Image->width; j++)
        {
            // 该点的色度H
            double dH = cvmGet( HSI_H, i, j );
            // 该点的色饱和度S
            double dS = cvmGet( HSI_S, i, j );
            // 该点的亮度
            double dI = cvmGet( HSI_I, i, j );

            double dTempB, dTempG, dTempR;
            // RG扇区
            if(dH < 120 && dH >= 0)
            {
                // 将H转为弧度表示
                dH = dH * 3.1415926 / 180;
                dTempB = dI * (1 - dS);
                dTempR = dI * ( 1 + (dS * cos(dH))/cos(3.1415926/3 - dH) );
                dTempG = (3 * dI - (dTempR + dTempB)); 
            }
            // GB扇区
            else if(dH < 240 && dH >= 120)
            {
                dH -= 120;
                                
                // 将H转为弧度表示
                dH = dH * 3.1415926 / 180;

                dTempR = dI * (1 - dS);
                dTempG = dI * (1 + dS * cos(dH)/cos(3.1415926/3 - dH));
                dTempB = (3 * dI - (dTempR + dTempG));
            }
            // BR扇区
            else 
            {
                dH -= 240;

                // 将H转为弧度表示
                dH = dH * 3.1415926 / 180;

                dTempG = dI * (1 - dS);
                dTempB = dI * (1 + (dS * cos(dH))/cos(3.1415926/3 - dH));
                dTempR = (3* dI - (dTempG + dTempB));
            }

            iB = dTempB * 255;
            iG = dTempG * 255;
            iR = dTempR * 255;

            cvSet2D( RGB_Image, i, j, cvScalar( iB, iG, iR ) );
        }
    }

    return RGB_Image;
}


int main()
{
    IplImage* img = cvLoadImage("lena.bmp");

    // 三个HSI空间数据矩阵
    CvMat* HSI_H = cvCreateMat( img->height, img->width, CV_32FC1 );
    CvMat* HSI_S = cvCreateMat( img->height, img->width, CV_32FC1 );
    CvMat* HSI_I = cvCreateMat( img->height, img->width, CV_32FC1 );

    // 原始图像数据指针, HSI矩阵数据指针
    uchar* data;

    // rgb分量
    byte img_r, img_g, img_b;
    byte min_rgb;  // rgb分量中的最小值
    // HSI分量
    float fHue, fSaturation, fIntensity; 

    for(int i = 0; i < img->height; i++)
    {
        for(int j = 0; j < img->width; j++)
        {
             data = cvPtr2D(img, i, j, 0);  
             img_b = *data;
             data++;
             img_g = *data;
             data++;
             img_r = *data;

             // Intensity分量[0, 1]
             fIntensity = (float)((img_b + img_g + img_r)/3)/255;

             // 得到RGB分量中的最小值
             float fTemp = img_r < img_g ? img_r : img_g;
             min_rgb = fTemp < img_b ? fTemp : img_b;
             // Saturation分量[0, 1]
             fSaturation = 1 - (float)(3 * min_rgb)/(img_r + img_g + img_b);

             // 计算theta角
             float numerator = (img_r - img_g + img_r - img_b ) / 2;
             float denominator = sqrt( 
                 pow( (img_r - img_g), 2 ) + (img_r - img_b)*(img_g - img_b) );

             // 计算Hue分量
             if(denominator != 0)
             {
                 float theta = acos( numerator/denominator) * 180/3.14;
                 
                 if(img_b <= img_g)
                 {
                     fHue = theta ;
                 }
                 else
                 {
                     fHue = 360 - theta;
                 }
             }
             else
             {
                 fHue = 0;
             }

             // 赋值
             cvmSet( HSI_H, i, j, fHue );
             cvmSet( HSI_S, i, j, fSaturation);
             cvmSet( HSI_I, i, j, fIntensity );
        }
    }

    IplImage* HSI_Image = catHSImage( HSI_H, HSI_S, HSI_I );
    IplImage* RGB_Image = HSI2RGBImage( HSI_H, HSI_S, HSI_I );

    cvShowImage("img", img);
    cvShowImage("HSI Color Model", HSI_Image);
    cvShowImage("RGB Color Model", RGB_Image);

    cvWaitKey(0);

    cvReleaseImage( &img );
    cvReleaseImage( &HSI_Image );
    cvReleaseImage( &RGB_Image );
    cvReleaseMat( &HSI_H);
    cvReleaseMat( &HSI_S);
    cvReleaseMat( &HSI_I);

    cvDestroyAllWindows();

    return 0;
}