CODEWITHSUNDEEP
c#opencvbitmapc++-climat
Ben
Ben

Reputation: 11

How do I transform Bitmap object into Mat object(opencv)?

I need to pass a Bitmap to dll created in C++ with opencv. In the dll I use Mat object for processing the image. I would want to know how can I change the Bitmap object into a Mat object. I tried using IntPtr but I do not know how to build the Mat object since the Mat constructor does not support IntPtr. Does anyone know how can I do this? It would be best if you could help me with a piece of code. Thanks.

Upvotes: 0

Views: 2303

Answers (2)

Ben
Ben

Reputation: 11

Thank you for your help! I found another way to do it. Check my code: C#:

 [DllImport("addborders.dll", CallingConvention = CallingConvention.Cdecl)]
    public static extern int main(IntPtr pointer, uint height,uint width);




 unsafe
        {
            fixed (byte* p = ImageToByte(img))
            {
                var pct = (IntPtr) p;
                 x = main(pct, (uint)img.Height, (uint)img.Width);

            }
            textBox1.Text = x.ToString();

 public static byte[] ImageToByte(Image img)
    {
        ImageConverter converter = new ImageConverter();
        return (byte[])converter.ConvertTo(img, typeof(byte[]));
    }

C++

  extern "C"
{
__declspec(dllexport)  
 int main(unsigned char* image,unsigned int height,unsigned int width)
{

    cv::Mat img = cv::Mat(height, width, CV_8UC1, image);
 }
}

Upvotes: 1

Evgeny
Evgeny

Reputation: 305

A simple way to do it is:

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>

using namespace System;
using namespace System::Drawing;

int main(array<System::String ^> ^args) {
    Bitmap^ img = gcnew Bitmap(10, 10,     System::Drawing::Imaging::PixelFormat::Format24bppRgb);
    // or: Bitmap^ img = gcnew Bitmap("input_image_file_name");

    System::Drawing::Rectangle blank = System::Drawing::Rectangle(0, 0, img->Width, img->Height);
    System::Drawing::Imaging::BitmapData^ bmpdata = img->LockBits(blank, System::Drawing::Imaging::ImageLockMode::ReadWrite,     System::Drawing::Imaging::PixelFormat::Format24bppRgb);
    cv::Mat cv_img(cv::Size(img->Width, img->Height), CV_8UC3, bmpdata->Scan0.ToPointer(), cv::Mat::AUTO_STEP);
    img->UnlockBits(bmpdata);

    cv::imwrite("image.png", cv_img);
    return 0;
}

BTW, it is worth to mention in the question that you are working with C++/CLI.

Upvotes: 3

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