Change image type : Convert 8U to 32F or 64F

void Mat::convertTo(OutputArray m, int rtype, double alpha=1, double beta=0 )

Parameters:

• m – output matrix; if it does not have a proper size or type before the operation, it is reallocated.
• rtype – desired output matrix type or, rather, the depth since the number of channels are the same as the input has; if rtype is negative, the output matrix will have the same type as the input.
• alpha – optional scale factor.
• beta – optional delta added to the scaled values.

saturate_cast<> is applied at the end to avoid possible overflows:

Steps:

1. Load an image 
2. Convert image type
3. Show result

Functions:

convertTo, imshow, imread, namedWindow, waitKey.

Example:

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#include "opencv2/core/core.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "iostream"

using namespace cv;
using namespace std;

int main( )
{

    Mat src1;
    src1 = imread("lena.jpg", CV_LOAD_IMAGE_COLOR); 
    namedWindow( "Original image", CV_WINDOW_AUTOSIZE ); 
    imshow( "Original image", src1 ); 
    Mat dst,dst1;
    // Change image type from 8UC1 to 32FC1
    src1.convertTo(dst, CV_32F);

    cout << "src1 intensity = " << (int) src1.at<Vec3b>(2,5)[0] << endl << "dst intensity = " << dst.at<Vec3f>(2,5)[0] <<endl << endl;
    // both intensity are same, but one is 8U and other is 32F

    dst.convertTo(dst1,CV_8U,1.5,10); // converting back to 8U with scaling
    namedWindow( "dst1", CV_WINDOW_AUTOSIZE );  
    imshow( "dst1", dst1 );
    
    waitKey(0);                                         
    return 0;
}

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