不正确的输出 RGB 到 HSI 转换答案

【问题标题】：incorrect output RGB to HSI convertion不正确的输出 RGB 到 HSI 转换
【发布时间】：2013-03-16 16:08:11
【问题描述】：

我正在尝试将给定图像的 RGB 转换为 HSI。但我似乎无法获得正确的输出。强度已经是正确的。但是，只要 R + G + B 不等于 765，色相和饱和度就会一直给出相同的结果 -2147483648。我用这个计算器检查过： http://www.had2know.com/technology/hsi-rgb-color-converter-equations.html 并使用了这个公式： http://web2.clarkson.edu/class/image_process/RGB_to_HSI.pdf 请指出我做错了什么。谢谢。

#include <iostream>
#include <cv.h>
#include <highgui.h>
#include "rgb.h"
#include <cmath>
#include <math.h>
#include <algorithm> 
using namespace std;


int main()
{
  char infname[256];

  cout << "Enter input image  : ";
  cin >> infname;
  IplImage *img = cvLoadImage(infname, 0);
  RgbImage pic(img);
  int H = img->height;
  int W = img->width;

 for (int j=0;j<H;j++) 
 for (int i=0;i<W;i++) {
            const double PI = 4.0*atan(1.0);
        double norm = 0;
        double R =(double) pic[j][i].r;
        double G =(double) pic[j][i].g;
        double B =(double) pic[j][i].b;
        double omega = 0;
        double intensity = 0;
        double hue = 0;
        double saturation = 0;
            double r = 0;
            double g = 0;
            double b = 0;

        //Intensity
        intensity = (double) (R + G + B) / (3.0*255);         

        //norm colours
        norm = sqrt(pow(r,2) + pow(g,2) + pow(b,2));
        r = (double) (R / norm);
        g = (double) (G / norm);
        b = (double) (B / norm);

        //Saturation and Hue
        if (R + G + B == 765) {
            saturation = 0;
            hue = 0;
        }

        else {
            double tmp = min(r, min(g, b));
            saturation = 1.0 - ((3.0 * tmp)/ (double)(r + g + b));
               if (saturation < 0.5 ){
                 saturation = 0;
                    }
                else if (saturation >= 0.5){
                 saturation = 1;
                  }
             }
        if (saturation != 0) {
            omega = 0.5 * ((r-g) + (r-b)) / sqrt(pow ((r-g),2) + (r-b)*(g-b));
            omega = acos(omega);
            if (B <= G) {
                hue = omega;
            }
            else if (B > G) {
                hue = 2 * PI - omega;
            }
        }

        //convert it to degrees
        int resultHue = (int) round((hue * 180.0) / PI);
        int resultSaturation = (int) (saturation*100.0);
        int resultIntensity = (int) round(intensity * 255);

cout<<"Red = "<<R<<", Green = "<<G<<", Blue =  "<<B<<endl;
cout<<"Hue  = "<<resultHue<<", Saturation = "<<resultSaturation<<", Intensity = "<<resultIntensity<<endl;


}

   return 0;
    }

【问题讨论】：

标签： c++ opencv image-manipulation

【解决方案1】：

您使用r、g 和b 计算norm，但此时它们始终为0。

【讨论】：

更多 cmets：使用r*r 比使用pow(r,2) 更好，因为后者要慢得多。不知道你为什么用一些复杂的方法来计算 PI； M_PI 还不够好吗？整数运算比浮点运算更快且优化得更好，因此您应该尽可能使用它。最后，我相信 openCV 已经内置了这个功能，那你为什么要从头开始呢？！
这项任务需要从头开始。
非常感谢大家！我遵循了你所有的答案，我做对了。稍后我会发布代码，希望对其他人有所帮助。 ;)
@Dave OPencv 有 RGB 到 HSV 和 RGB 到 HLS，但没有 RGB 到 HSI。请参阅：docs.opencv.org/2.4/modules/imgproc/doc/… 如果我错了，请更正。谢谢。

【解决方案2】：

#include <iostream>
#include <cv.h>
#include <highgui.h>
#include "rgb.h"
#include <cmath>
#include <algorithm> 
#include <fstream>
using namespace std;


int main()
{
  char infname[256];
  ofstream outputFile;
  outputFile.open("RGB_HSI.txt");

  cout << "Enter input image  : ";
  cin >> infname;
  IplImage *img = cvLoadImage(infname, 0);
  RgbImage pic(img);
  int H = img->height;
  int W = img->width;


 for (int j=0;j<H;j++) 
 for (int i=0;i<W;i++) {
        double norm = 0;
        double omega = 0;
        double R =(double) pic[j][i].r;
        double G =(double) pic[j][i].g;
        double B =(double) pic[j][i].b;
        double intensity = 0;
        double hue = 0;
        double saturation = 0;
            double r = 0;
            double g = 0;
            double b = 0;
            int resultHue = 0;
            int resultSaturation = 0;
            int resultIntensity = 0;

        //Intensity
        intensity = (double) (R + G + B) / (3.0*255);         

        //norm colours
        norm = sqrt((R*R) + (G*G) + (B*B));
        r = (double) (R / norm);
        g = (double) (G / norm);
        b = (double) (B / norm);

        //Saturation and Hue
        if (R + G + B == 765) {
            saturation = 0;
            hue = 0;
        }

        else {
            double tmp = min(r, min(g, b));
            saturation = 1.0 - ((3.0 * tmp)/ (double)(r + g + b));
               if (saturation < 0.5 ){
                 saturation = 0;
                    }
                else if (saturation >= 0.5){
                 saturation = 1;
                  }
             }
        if (saturation != 0) {
            omega = 0.5 * ((r-g) + (r-b)) / sqrt(((r-g) * (r-g)) + (r-b)*(g-b));
            omega = acos(omega);
            if (B <= G) {
                hue = omega;
            }
            else if (B > G) {
                hue = 2 * M_PI - omega;
            }
        }

        //convert it to degrees
         resultHue = (int) round((hue * 180.0) / M_PI);
         resultSaturation = (int) (saturation);
         resultIntensity = (int) round(intensity * 255);

           if ((R == 0) && (G == 0) && ( B== 0 )) {
              resultHue = 0;
              resultSaturation = 0;
              resultIntensity = 0;
            }

outputFile<<"Red = "<<R<<", Green = "<<G<<", Blue =  "<<B<<endl;
outputFile<<"Hue  = "<<resultHue<<", Saturation = "<<resultSaturation<<", Intensity = "<<resultIntensity<<endl;


}
outputFile.close();
cout << "\nRGB_HSI printed as text file: RGB_HSI.text\n";

   return 0;
    }

【讨论】：