rotate.cpp

#include <cmath>
#include <algorithm>

#include "box.h"
#include "math.h"
#include "rotate.h"
#include "options.h"

// Find top left and bottom right box. Then, determine slope of these two
// and return the amount to rotate.
double findRotation(const Pixels& img, const std::vector<Coord>& boxes, Coord& ret_coord)
{
    Coord top;
    Coord bottom;

    // Set to max large values
    double min_top_dist    = img.height();
    double min_bottom_dist = img.height();

    // Top and bottom points
    const Coord topleft(0, 0);
    const Coord bottomleft(0, img.height() - 1);

    // Find closest box to top and bottom left
    for (const Coord& c : boxes)
    {
        double dist_top    = distance(c, topleft);
        double dist_bottom = distance(c, bottomleft);

        if (dist_top < min_top_dist)
        {
            top = c;
            min_top_dist = dist_top;
        }

        if (dist_bottom < min_bottom_dist)
        {
            bottom = c;
            min_bottom_dist = dist_bottom;
        }
    }

    // Determine angle from slope of line going through those two boxes
    double angle = 0;
    ret_coord = top;

    // If denominator is zero, don't rotate
    if (top.y != bottom.y)
        angle = std::atan((1.0*bottom.x - top.x)/(1.0*bottom.y - top.y));

    return angle;
}