Valeur négative lors du calcul de la variance d'une image -java-

Ici, j'essaie de calculer la variance d'une image

Donc, j'ai essayé d'appliquer les deux méthodes (de calcule de variance var (x) = E (x²) -E (x) ² and ∑1/n [(x[i]-x̅) ²] pour vérifier si cela fonctionne Pour
l'image 1 les deux valeurs de la varinace étaient identiques
Mais avec l'image 2, j'ai obtenu une valeur négative pour la méthode 2

Code:

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private void openActionPerformed(java.awt.event.ActionEvent evt) {
    LoadImage loadImage = new LoadImage(null);
    int w = 0, h = 0;
    BufferedImage image;
    float somR = 0;
    int somG = 0;
    int somB = 0;
    int valR[][];
    int[][] valG;
    int valB[][];
    float meanR = 0;
    float meanG = 0;
    float meanB = 0;
    int nbpixl = 0;
 
    float square_Red = 0, square_Blue = 0, square_Green = 0;
    //The sum of pixels for each color
    int sum_Square_Red = 0, sum_Square_Blue = 0, sum_Square_Green = 0;
    // The square sum of the pixels for each color
    float varR = 0, varG = 0, varB = 0;//The variance of each color
    try {
        if (loadImage.loadImage(jScrollPane1)) {
            int pixel = 0;
 
            image = loadImage.getImage();
            w = image.getWidth();
            h = image.getHeight();
            System.out.println("width, height: " + w + ", " + h);
            nbpixl = w * h;
 
            valR = new int[h][w];
            valB = new int[h][w];
            valG = new int[h][w];
            for (int i = 0; i < h; i++) {
                for (int j = 0; j < w; j++) {
                    pixel = image.getRGB(j, i);
                    int red = (pixel >> 16) & 0xff;
                    int green = (pixel >> 8) & 0xff;
                    int blue = (pixel) & 0xff;
 
                    valR[i][j] = red;
                    somR += red;
 
                    square_Red = red * red;
                    sum_Square_Red += square_Red;
 
                    valG[i][j] = green;
                    somG += green;
 
                    square_Green = green * green;
                    sum_Square_Green += square_Green;
 
                    valB[i][j] = blue;
                    somB += blue;
 
                    square_Blue = blue * blue;
                    sum_Square_Blue += square_Blue;
 
                }
 
            }
 
            //la moyenne de pixels dechaque couleurs
            meanR = somR / nbpixl;
            meanG = somG / nbpixl;
            meanB = somB / nbpixl;
            //meanB = somB / nbpixl * 255.0f;
 
            //1  method of calculating the variance
            System.out.println("1 method of calculating the variance\n");
            float var[] = new float[3];
            for (int i = 0; i < h; i++) {
                for (int j = 0; j < w; j++) {
 
                    varR += (meanR - valR[i][j]) * (meanR - valR[i][j]);
                    varG += (meanG - valG[i][j]) * (meanG - valG[i][j]);
                    varB += (meanR - valB[i][j]) * (meanB - valB[i][j]);
 
                }
 
            }
 
            var[0] = (varR / nbpixl);
 
            var[1] = (varG / nbpixl);
 
            var[2] = (varB / nbpixl);
 
            float var_img = ((var[0] + var[1] + var[2]) / nbpixl);
 
             System.out.println("var=\t"+var[0] + "\t"+ var[1] + "\t"+                                                                  var[2]);
            System.out.println("var of image=\t" + var_img);
 
            //2 method of calculating the variance
            System.out.println("2 method of calculating the variance\n");
 
            float varR1 = sum_Square_Red / nbpixl - (meanR * meanR);
            float varG1 = sum_Square_Green / nbpixl - (meanG * meanG);
            float varB1 = sum_Square_Blue / nbpixl - (meanB * meanB);
            float mean_img1 = ((varR1 + varG1 + varB1) / nbpixl);
 
       System.out.println("var=\t" + varR1 + "\t" + varG1 + "\t" + varB1);
            System.out.println("var of image=\t" + mean_img1);
 
        }
 
    } catch (IOException ex) {
        Logger.getLogger(var_img1.class.getName()).log(Level.SEVERE, null, ex);
    }
}

et pour le resultat

Width, height: 259, 194

1 method of calculating the variance

varR= 7598.217 varG= 5033.452 varB= 4910.8223

Var of picture = 0.34913212

2 method of calculating the variance

varR= 7597.9395 varG= 5183.0 varB= 4994.0

Var of image = 0.3537583

******************************************************************

And for image 2

width, height: 620, 349 1 method of calculating the variance

varR= 991.2626 varG= 1525.1627 varB= 1280.9857

var of image= 0.017549733

2 method of calculating the variance

varR= -52462.875 varG= -50101.0 varB= -50592.0

var of image= -0.70780975