/******************************************************************/
/* This file is part of the homework assignments for CSCI-427/527 */
/* at The College of William & Mary and authored by Pieter Peers. */
/* No part of this file, whether altered or in original form, can */
/* be distributed or used outside the context of CSCI-427/527     */
/* without consent of either the College of William & Mary or     */
/* Pieter Peers.                                                  */
/******************************************************************/
#include "bilinearTexture.h"


//////////////////
// Constructors //
//////////////////
bilinearTexture::bilinearTexture(bool repeat)
  : texture_base(repeat)
{
  // Do nothing.
}


bilinearTexture::bilinearTexture(const bilinearTexture& src)
  : texture_base(src)
{
  // Do nothing
}


///////////////
// Operators //
///////////////
bilinearTexture& bilinearTexture::operator=(const bilinearTexture& src)
{
  _assign(src);
  return *this;
}


image::value_type bilinearTexture::operator()(const vec2d& textureCoord) const
{
  // HW5: Implement a bilinear texture evaluation. Given a texture coordinate
  //      return the bilinearly interpolate the color.
  // Modifes: nothing.
  // Returns: color.
  
  vec2d::value_type x, y, x1, x2, y1, y2, dx, dy;
  color a, b;

  x = textureCoord.u * (image::width() - 1);
  y = textureCoord.v * (image::height() - 1);
  x1 = floor(x);
  x2 = x1 + 1;
  y1 = floor(y);
  y2 = y1 + 1;
  dx = x - x1;
  dy = y - y1;
  a = _at(x1, y1) * (1 - dx) + _at(x2, y1) * dx;
  b = _at(x1, y2) * (1 - dx) + _at(x2, y2) * dx;
  return  a * (1 - dy) + b * (dy);
}


/////////////////////
// Private Methods //
/////////////////////
void bilinearTexture::_print(std::ostream& s) const
{
  s << "Bilinear texture (" << this->width() << "x" << this->height() << ")";
}