Question

I need to send an image into a byte array using c++/cli. The image is initially in Iplimage format.

    int img_sz1 = img1->width * img1->height * img1->nChannels;
    array <Byte>^ hh1 = gcnew array<Byte> (img_sz1);
    Marshal::Copy( (IntPtr)img->imageData, hh1, 0, img_sz1 );

and it was working fine.

I added the encoding step to send it as jpeg

    CvMat* buf1 = cvEncodeImage(".jpeg", img1, jpeg_params);
    img_sz1=buf1->width*buf1->height 
    Marshal::Copy( (IntPtr)buf1, hh1, 0, img_sz1 );

and now it compiles fine but gives me the error at the marshal:copy line

 An unhandled exception of type 'System.AccessViolationException' occurred in   
 mscorlib.dll. Additional information: Attempted to read or write protected memory. 

Any help is very appreciated.

Answer 1

The return of cvEncodeImage is a single-row matrix, containing the encoded image data. What you’re copying now is the struct itself, e.g., the width field, the height field, etc. I believe you need to copy from buf1->data instead.