c++ - 查找图像上的主色

Question

我想在图像上找到主色。为此，我知道我应该使用图像直方图。但我不确定图像格式。应该使用 rgb、hsv 还是灰度图像中的哪一个？

计算直方图后，我应该在直方图上找到最大值。为此，我应该找到 hsv 图像的最大 binVal 值以下吗？为什么我的结果图像只包含黑色？

float binVal = hist.at<float>(h, s);

编辑:

我试过下面的代码。我绘制 h-s 直方图。我的结果图片在这里。在二进制阈值之后我没有找到任何东西。也许我错误地找到了最大直方图值。

cvtColor(src, hsv, CV_BGR2HSV);

// Quantize the hue to 30 levels
// and the saturation to 32 levels
int hbins = 20, sbins = 22;
int histSize[] = {hbins, sbins};
// hue varies from 0 to 179, see cvtColor
float hranges[] = { 0, 180 };
// saturation varies from 0 (black-gray-white) to
// 255 (pure spectrum color)
float sranges[] = { 0, 256 };
const float* ranges[] = { hranges, sranges };
MatND hist;
// we compute the histogram from the 0-th and 1-st channels
int channels[] = {0, 1};

calcHist( &hsv, 1, channels, Mat(), // do not use mask
         hist, 2, histSize, ranges,
         true, // the histogram is uniform
         false );
double maxVal=0;
minMaxLoc(hist, 0, &maxVal, 0, 0);

int scale = 10;
Mat histImg = Mat::zeros(sbins*scale, hbins*10, CV_8UC3);
int maxIntensity = -100;
for( int h = 0; h < hbins; h++ ) {
    for( int s = 0; s < sbins; s++ )
    {
        float binVal = hist.at<float>(h, s);
        int intensity = cvRound(binVal*255/maxVal);
        rectangle( histImg, Point(h*scale, s*scale),
                    Point( (h+1)*scale - 1, (s+1)*scale - 1),
                    Scalar::all(intensity),
                    CV_FILLED );
        if(intensity > maxIntensity)
            maxIntensity = intensity;
    }
}
std::cout << "max Intensity " << maxVal << std::endl;
Mat dst;
cv::threshold(src, dst, maxIntensity, 255, cv::THRESH_BINARY);

namedWindow( "Dest", 1 );
imshow( "Dest", dst );
namedWindow( "Source", 1 );
imshow( "Source", src );

namedWindow( "H-S Histogram", 1 );
imshow( "H-S Histogram", histImg );

Answer 1

或者您可以尝试 k-means方法。 Calculate k clusters使用 k ~ 2..5 并以最大组的质心作为主色。

OpenCv 的 python 文档有一个 illustrated example很好地获得主色: