I created a C DLL out of my C++ class which uses OpenCV for image manipulations and want to use this dll in my C# application.
Currently, this is how I have implemented it :
#ifdef CDLL2_EXPORTS
#define CDLL2_API __declspec(dllexport)
#else
#define CDLL2_API __declspec(dllimport)
#endif
#include "../classification.h"
extern "C"
{
CDLL2_API void Classify_image(unsigned char* img_pointer, unsigned int height, unsigned int width, char* out_result, int* length_of_out_result, int top_n_results = 2);
//...
}
C# related code :DLL Import section:
//Dll import
[DllImport(@"CDll2.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
static extern void Classify_Image(IntPtr img, uint height, uint width, byte[] out_result, out int out_result_length, int top_n_results = 2);
The actual function sending the image to the DLL:
//...
//main code
private string Classify(int top_n)
{
byte[] res = new byte[200];
int len;
Bitmap img = new Bitmap(txtImagePath.Text);
BitmapData bmpData = img.LockBits(new Rectangle(0, 0, img.Width, img.Height),
ImageLockMode.ReadWrite,
PixelFormat.Format24bppRgb);
Classify_Image(bmpData.Scan0, (uint)bmpData.Height, (uint)bmpData.Width, res, out len, top_n);
img.UnlockBits(bmpData); //Remember to unlock!!!
//...
}
and the C++ code in the DLL :
CDLL2_API void Classify_Image(unsigned char* img_pointer, unsigned int height, unsigned int width,
char* out_result, int* length_of_out_result, int top_n_results)
{
auto classifier = reinterpret_cast(GetHandle());
cv::Mat img = cv::Mat(height, width, CV_8UC3, (void*)img_pointer, Mat::AUTO_STEP);
std::vector result = classifier->Classify(img, top_n_results);
//...
*length_of_out_result = ss.str().length();
}
This works prefectly with some images but it doesnt work with others, for example when I try to imshow the image in the Classify_Image, right after being created form the data sent by C# application, I am faced with images like this :
problematic example:
fine example :
Here are the original images for further investigations(may be nsfw for some people so I place the link) :
http://answers.opencv.org/upfiles/15029729463967486.jpg
http://answers.opencv.org/upfiles/15029729777606505.jpg
My own thought about the cause of the issue, is I am creating the image regardless of its true type, (setting all images to `CV_8UC3` and `Mat::AUTO_STEP`. thats why some images are fine and some others are not.
The problem is, I dont know how I'm supposed to assign the correct type to each image at creation time back in C++. (if thats the cause for such issue, if it is not then I have no idea what else could be doing this)
Any help is greatly appreciated .
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