/******************************************************************/
/* 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
{
  float scaled_u = textureCoord.u*(width()-1);
  float scaled_v = textureCoord.v*(height()-1);

  // compute corners
  signed int left = floor(scaled_u);
  signed int right = ceil(scaled_u);
  signed int top = floor(scaled_v);
  signed int bottom = ceil(scaled_v);

  // compute weights
  float hw = fabs(right - scaled_u);
  float vw = fabs(bottom - scaled_v);

  // compute horizontal interpolated colors
  color topColor = hw * _at(left, top) + (1.0f - hw) * _at(right, top);
  color bottomColor = hw * _at(left, bottom) + (1.0f - hw) * _at(right, bottom);

  // interpolate vertically
  return vw * topColor + (1.0f - vw) * bottomColor;
}


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