Calling userdefined functions in thrust

I'm loading a .png file using OpenCV and I want to extract its blue intensity values using thrust library.

My code goes like this:

1. Loading an image using OpenCV IplImage pointer
2. Copying the image data into thrust::device_vector
3. Extracting the blue intensity values from the device vector inside a structure using thrust library.

Now I have a problem in extracting Blue Intensity values from the device vector.

• I did this code in cuda already now converting it using thrust library.
• I fetch blue intensity values inside this function.
• I want to know how to call this struct FetchBlueValues from the main function.

Code:

#define ImageWidth 14 #define ImageHeight 10 thrust::device_vector<int> BinaryImage(ImageWidth*ImageHeight); thrust::device_vector<int> ImageVector(ImageWidth*ImageHeight*3); struct FetchBlueValues { __host__ __device__ void operator() () { int index = 0 ; for(int i=0; i<= ImageHeight*ImageWidth*3 ; i = i+3) { BinaryImage[index]= ImageVector[i]; index++; } } }; void main() { src = cvLoadImage("../Input/test.png", CV_LOAD_IMAGE_COLOR); unsigned char *raw_ptr,*out_ptr; raw_ptr = (unsigned char*) src->imageData; thrust::device_ptr<unsigned char> dev_ptr = thrust::device_malloc<unsigned char>(ImageHeight*src->widthStep); thrust::copy(raw_ptr,raw_ptr+(src->widthStep*ImageHeight),dev_ptr); int index=0; for(int j=0;j<ImageHeight;j++) { for(int i=0;i<ImageWidth;i++) { ImageVector[index] = (int) dev_ptr[ (j*src->widthStep) + (i*src->nChannels) + 0 ]; ImageVector[index+1] = (int) dev_ptr[ (j*src->widthStep) + (i*src->nChannels) + 1 ]; ImageVector[index+2] = (int) dev_ptr[ (j*src->widthStep) + (i*src->nChannels) + 2 ]; index +=3 ; } } }