opencv 图像的水平积分投影和垂直积分投影（用于拟合线段确定或者目标提取）

对于需要确定拟合线段（哪几个线段进行拟合）或者目标提取，常常用到投影法。

#include  
#include  
using namespace cv;  
Mat VerticalProjection(Mat srcImage)//垂直积分投影  
{  
    if (srcImage.channels() > 1)  
        cvtColor(srcImage, srcImage, CV_RGB2GRAY);  
    Mat srcImageBin;  
    threshold(srcImage, srcImageBin, 120, 255, CV_THRESH_BINARY_INV);  
    imshow("二值图", srcImageBin);  
    int *colswidth = new int[srcImage.cols];  //申请src.image.cols个int型的内存空间  
    memset(colswidth, 0, srcImage.cols * 4);  //数组必须赋初值为零，否则出错。无法遍历数组。  
    //  memset(colheight,0,src->width*4);    
    // CvScalar value;   
    int value;  
    for (int i = 0; i < srcImage.cols; i++)  
    for (int j = 0; j < srcImage.rows; j++)  
    {  
        //value=cvGet2D(src,j,i);  
        value = srcImageBin.at(j, i);  
        if (value == 255)  
        {  
            colswidth[i]++; //统计每列的白色像素点    
        }  
    }  
    Mat histogramImage(srcImage.rows, srcImage.cols, CV_8UC1);  
    for (int i = 0; i < srcImage.rows; i++)  
    for (int j = 0; j < srcImage.cols; j++)  
    {  
        value = 255;  //背景设置为白色。   
        histogramImage.at(i, j) = value;  
    }  
    for (int i = 0; i < srcImage.cols; i++)  
    for (int j = 0; j < colswidth[i]; j++)  
    {  
        value = 0;  //直方图设置为黑色  
        histogramImage.at(srcImage.rows - 1 - j, i) = value;  
    }  
    imshow(" 垂直积分投影图", histogramImage);  
    return histogramImage;  
}  
Mat HorizonProjection(Mat srcImage)//水平积分投影  
{  
    if (srcImage.channels() > 1)  
        cvtColor(srcImage, srcImage, CV_RGB2GRAY);  
    Mat srcImageBin;  
    threshold(srcImage, srcImageBin, 120, 255, CV_THRESH_BINARY_INV);  
    imshow("二值图", srcImageBin);  
    int *rowswidth = new int[srcImage.rows];  //申请src.image.rows个int型的内存空间  
    memset(rowswidth, 0, srcImage.rows * 4);  //数组必须赋初值为零，否则出错。无法遍历数组。  
    int value;  
    for (int i = 0; ifor (int j = 0; j//value=cvGet2D(src,j,i);  
        value = srcImageBin.at(i, j);  
        if (value == 255)  
        {  
            rowswidth[i]++; //统计每行的白色像素点    
        }  
    }  
    Mat histogramImage(srcImage.rows, srcImage.cols, CV_8UC1);  
    for (int i = 0; ifor (int j = 0; jvalue = 255;  //背景设置为白色。   
        histogramImage.at(i, j) = value;  
    }  
    //imshow("d", histogramImage);  
    for (int i = 0; ifor (int j = 0; jvalue = 0;  //直方图设置为黑色  
        histogramImage.at(i, j) = value;  
    }  
    imshow("水平积分投影图", histogramImage);  
    delete[] rowswidth;//释放前面申请的空间  
    return histogramImage;  

}