Shrink image using C++

Question

I've been trying to shrink an image just using C++. I am quite new to this language.

This is what I have and it works but there is a problem where it leaves unwanted pixels behind.

    Rgb temp;
    float scale = 0.8;
    for(int y = 0; y < h*scale; y++)
    {
        int scaleY = (int)(y/scale);
        for(int x = 0; x < w*scale; x++) {
            int scaleX = (int) (x / scale);
            temp = pixels[x + y * w];
            pixels[x + y * w] = pixels[scaleX + scaleY * w];
            pixels[scaleX + scaleY * w] = temp;
        }
    }

I have been looking online and haven't found many examples that just use basic C++. I'd appreciate any help.