calling c++ function in c#

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C++

C#

Hi following is the code example. Please suggest what should I do to call c++ written function to a c# function.
Thank you in advance
c++ code

// type defs. for Graphic Gemms Code - see later

#define BYTE_IMAGE

#ifdef BYTE_IMAGE
typedef unsigned char kz_pixel_t;        /* for 8 bit-per-pixel images */
#define uiNR_OF_GREY (256)
#else
typedef unsigned short kz_pixel_t;       /* for 12 bit-per-pixel images (default) */
# define uiNR_OF_GREY (4096)
#endif
static int CLAHE (kz_pixel_t* pImage, unsigned int uiXRes, unsigned int uiYRes,
         kz_pixel_t Min, kz_pixel_t Max, unsigned int uiNrX, unsigned int uiNrY,
              unsigned int uiNrBins, float fCliplimit)
 {
...
...
}

c# calling code

csharpfunction()
{
CLAHE((byte*)im, 0, 0, 0, 0, 0, 0, 0, 0.02);
}

im is image instance. the c++ code gets the pointer in byte formate. how can I convert the referece to my image object to pass in the function as byte*.
Please help will be very thankful to you.