quadratc.h

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/**********************************************************************
 * File:        quadratc.h  (Formerly quadrtic.h)
 * Description: Code for the QUAD_COEFFS class.
 * Author:      Ray Smith
 * Created:     Tue Oct 08 17:24:40 BST 1991
 *
 * (C) Copyright 1991, Hewlett-Packard Ltd.
 ** Licensed under the Apache License, Version 2.0 (the "License");
 ** you may not use this file except in compliance with the License.
 ** You may obtain a copy of the License at
 ** http://www.apache.org/licenses/LICENSE-2.0
 ** Unless required by applicable law or agreed to in writing, software
 ** distributed under the License is distributed on an "AS IS" BASIS,
 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 ** See the License for the specific language governing permissions and
 ** limitations under the License.
 *
 **********************************************************************/
 
#ifndef QUADRATC_H
#define QUADRATC_H
 
#include "points.h"
 
namespace tesseract {
 
class QUAD_COEFFS {
public:
  QUAD_COEFFS() = default;
  QUAD_COEFFS(    // constructor
      double xsq, // coefficients
      float x, float constant) {
    a = xsq;
    b = x;
    c = constant;
  }
 
  float y(             // evaluate
      float x) const { // at x
    return static_cast<float>((a * x + b) * x + c);
  }
 
  void move(        // reposition word
      ICOORD vec) { // by vector
    /************************************************************
  y - q = a (x - p)^2 + b (x - p) + c
  y - q = ax^2 - 2apx + ap^2 + bx - bp + c
    y = ax^2 + (b - 2ap)x + (c - bp + ap^2 + q)
************************************************************/
    int16_t p = vec.x();
    int16_t q = vec.y();
 
    c = static_cast<float>(c - b * p + a * p * p + q);
    b = static_cast<float>(b - 2 * a * p);
  }
 
  double a; // x squared
  float b;  // x
  float c;  // constant
private:
};
 
} // namespace tesseract
 
#endif