Question

I am working with images and computing radon transform for an object. The function that computes the transform accepts vector as input:

pixel p;
vector<pixel> segObj  //segObj is the object segmneted from the image

pixel is a user-defined struct defined as:

struct pixel
{
float x, y;  //x,y coordinates of the pixel
};

Currently, I am doing an element wise assignment to the vector:

for(int ix=0; ix < element_count; ix++)
{
f.x = xCoordArray[ix];
f.y = yCoordArray[ix];
segObj.push_back(f);
//xCoordArray and yCoordArray are computed separately
}

The for loop makes it slow when dealing with large images. Is there a way to assign xCoordArray and yCoordArray directly to vector<pixel>segObj

I am not expereinced with the use of vectors so any help would be appreciated.
Also,
If xCoordArray, yCoordArray can be computed as vectors, is there a way to join them so that each vector index as two values.

Answer 1

You can create an input iterator producing pixel objects and assign those directly. You could initialize the objects directly using something along the lines of this:

pixel iterator::operator*() const {
    pixel rc = {
        xCoordArray[index],
        tCoordArray[index]
    };
    return rc;
}

That said, I somewhat doubt that this is indeed the bottleneck: did you profile your code or are you suspecting that this is the problem?