CODEWITHSUNDEEP
c++opencv
feelfree
feelfree

Reputation: 11753

How to adjust empty cv::Mat object

I understand how to create a opencv Mat object supposed the pointer to the image pixels as well as some other auxiliary information is given. For example:

int width = 100;
int height = 200;
unsigned char *pPixel = new unsigned char [width*height];
cv::Mat myMat(height,width, CV_8UC1,pPixel);
delete []nPixel;

My next question is: suppose myMat already exists as an empty cv::Mat object, and in this case how can we assign image information to the empty myMat object? This can happen in the following function:

void create_mat(int width, int height, int band_num, unsigned char *pPixel, cv::Mat &obj)
{
   // adjust obj based on width, height and pPixel

}

EDIT:Possible solutions:

 void create_mat(int width, int height, int band_num, unsigned char *pPixel, cv::Mat &obj)
    {
        obj.data = pPixel;
        obj.rows = height;
        obj.cols = width;
           // how to assign image data type?

    }

Upvotes: 0

Views: 1083

Answers (3)

vinograd47
vinograd47

Reputation: 6420

Use the same constructor:

void create_mat(int width, int height, int band_num, unsigned char *pPixel, cv::Mat &obj)
{
    obj = cv::Mat(height, width, CV_8UC1, pPixel);
}

Upvotes: 0

fatihk
fatihk

Reputation: 7919

To assign data to an already initialized Mat object ,you can use std::copy:

std::copy(pPixel, pPixel + width*height, &obj.data[0]);

and if that matrix is already initialized with:

cv::Mat myMat(height,width, CV_8UC1);

You do not need any further modification to set data type.

Upvotes: 1

Simson
Simson

Reputation: 824

I'm not sure what band_num means, bu you could use

void create_mat(int width, int height, int band_num, unsigned char *pPixel, cv::Mat &obj)
{
   obj.create(width, height, type); // e.g. type: CV_8UC1
   obj.data = pPixel;
}

Upvotes: 1

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