///////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2007, Industrial Light & Magic, a division of Lucas
// Digital Ltd. LLC
// 
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
// *       Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// *       Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
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// its contributors may be used to endorse or promote products derived
// from this software without specific prior written permission. 
// 
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///////////////////////////////////////////////////////////////////////////


//-----------------------------------------------------------------------------
//
//	function blurImage() -- performs a hemispherical blur
//
//-----------------------------------------------------------------------------

#include "blurImage.h"

#include "namespaceAlias.h"

#include <resizeImage.h>
#include <cstring>
#include "Iex.h"
#include <iostream>
#include <algorithm>
#include <string.h>


using namespace IMF;
using namespace std;
using namespace IMATH;


inline int
toInt (float x)
{
    return int (x + 0.5f);
}


inline double
sqr (double x)
{
    return x * x;
}


void
blurImage (EnvmapImage &image1, bool verbose)
{
    //
    // Ideally we would blur the input image directly by convolving
    // it with a 180-degree wide blur kernel.  Unfortunately this
    // is prohibitively expensive when the input image is large.
    // In order to keep running times reasonable, we perform the
    // blur on a small proxy image that will later be re-sampled
    // to the desired output resolution.
    //
    // Here's how it works:
    //
    // * If the input image is in latitude-longitude format,
    //   convert it into a cube-face environment map.
    //
    // * Repeatedly resample the image, each time shrinking
    //   it to no less than half its current size, until the
    //   width of each cube face is MAX_IN_WIDTH pixels.
    // 
    // * Multiply each pixel by a weight that is proportinal
    //   to the solid angle subtended by the pixel as seen
    //   from the center of the environment cube.
    //
    // * Create an output image in cube-face format.
    //   The cube faces of the output image are OUT_WIDTH
    //   pixels wide.
    //
    // * For each pixel of the output image:
    //
    //       Set the output pixel's color to black
    //
    //       Determine the direction, d2, from the center of the
    //       output environment cube to the center of the output
    //	     pixel.
    //   
    //       For each pixel of the input image:
    //
    //           Determine the direction, d1, from the center of
    //           the input environment cube to the center of the
    //           input pixel.
    //    
    //           Multiply the input pixel's color by max (0, d1.dot(d2))
    //           and add the result to the output pixel.
    //

    const int MAX_IN_WIDTH = 40;
    const int OUT_WIDTH = 100;

    if (verbose)
	cout << "blurring map image" << endl;

    EnvmapImage image2;
    EnvmapImage *iptr1 = &image1;
    EnvmapImage *iptr2 = &image2;

    int w = image1.dataWindow().max.x - image1.dataWindow().min.x + 1;
    int h = w * 6;

    if (iptr1->type() == ENVMAP_LATLONG)
    {
	//
	// Convert the input image from latitude-longitude
	// to cube-face format.
	//

	if (verbose)
	    cout << "    converting to cube-face format" << endl;

	w /= 4;
	h = w * 6;

	Box2i dw (V2i (0, 0), V2i (w - 1, h - 1));
	resizeCube (*iptr1, *iptr2, dw, 1, 7);

	swap (iptr1, iptr2);
    }

    while (w > MAX_IN_WIDTH)
    {
	//
	// Shrink the image.
	//

	if (w >= MAX_IN_WIDTH * 2)
	    w /= 2;
	else
	    w = MAX_IN_WIDTH;

	h = w * 6;

	if (verbose)
	{
	    cout << "    resizing cube faces "
		    "to " << w << " by " << w << " pixels" << endl;
	}

	Box2i dw (V2i (0, 0), V2i (w - 1, h - 1));
	resizeCube (*iptr1, *iptr2, dw, 1, 7);

	swap (iptr1, iptr2);
    }

    if (verbose)
	cout << "    computing pixel weights" << endl;

    { 
        //
        // Multiply each pixel by a weight that is proportinal
        // to the solid angle subtended by the pixel.
        //

	Box2i dw = iptr1->dataWindow();
	int sof = CubeMap::sizeOfFace (dw);

	Array2D<Rgba> &pixels = iptr1->pixels();

	double weightTotal = 0;

	for (int f = CUBEFACE_POS_X; f <= CUBEFACE_NEG_Z; ++f)
	{
	    if (verbose)
		cout << "        face " << f << endl;

	    CubeMapFace face = CubeMapFace (f);
	    V3f faceDir (0, 0, 0);
            int ix = 0, iy = 0, iz = 0;

	    switch (face)
	    {
	      case CUBEFACE_POS_X:
		faceDir = V3f (1, 0, 0);
                ix = 0;
                iy = 1;
                iz = 2;
		break;

	      case CUBEFACE_NEG_X:
		faceDir = V3f (-1, 0, 0);
                ix = 0;
                iy = 1;
                iz = 2;
		break;

	      case CUBEFACE_POS_Y:
		faceDir = V3f (0, 1, 0);
                ix = 1;
                iy = 0;
                iz = 2;
		break;

	      case CUBEFACE_NEG_Y:
		faceDir = V3f (0, -1, 0);
                ix = 1;
                iy = 0;
                iz = 2;
		break;

	      case CUBEFACE_POS_Z:
		faceDir = V3f (0, 0, 1);
                ix = 2;
                iy = 0;
                iz = 1;
		break;

	      case CUBEFACE_NEG_Z:
		faceDir = V3f (0, 0, -1);
                ix = 2;
                iy = 0;
                iz = 1;
		break;
	    }

	    for (int y = 0; y < sof; ++y)
	    {
		bool yEdge = (y == 0 || y == sof - 1);

		for (int x = 0; x < sof; ++x)
		{
		    bool xEdge = (x == 0 || x == sof - 1);

		    V2f posInFace (x, y);

		    V3f dir =
			CubeMap::direction (face, dw, posInFace).normalized();

		    V2f pos =
			CubeMap::pixelPosition (face, dw, posInFace);

                    //
                    // The solid angle subtended by pixel (x,y), as seen
                    // from the center of the cube, is proportional to the
                    // square of the distance of the pixel from the center
                    // of the cube and proportional to the dot product of
                    // the viewing direction and the normal of the cube
                    // face that contains the pixel.
                    //

                    double weight =
                        (dir ^ faceDir) *
                        (sqr (dir[iy] / dir[ix]) + sqr (dir[iz] / dir[ix]) + 1);

                    //
                    // Pixels at the edges and corners of the
                    // cube are duplicated; we must adjust the
                    // pixel weights accordingly.
                    //

		    if (xEdge && yEdge)
			weight /= 3;
		    else if (xEdge || yEdge)
			weight /= 2;

		    Rgba &pixel = pixels[toInt (pos.y)][toInt (pos.x)];

		    pixel.r *= weight;
		    pixel.g *= weight;
		    pixel.b *= weight;
		    pixel.a *= weight;

		    weightTotal += weight;
		}
	    }
	}

	//
	// The weighting operation above has made the overall image darker.
	// Apply a correction to recover the image's original brightness.
	//

	int w = dw.max.x - dw.min.x + 1;
	int h = dw.max.y - dw.min.y + 1;
	size_t numPixels = w * h;
	double weight = numPixels / weightTotal;

	Rgba *p = &pixels[0][0];
	Rgba *end = p + numPixels;

	while (p < end)
	{
	    p->r *= weight;
	    p->g *= weight;
	    p->b *= weight;
	    p->a *= weight;

	    ++p;
	}
    } 

    { 
	if (verbose)
	    cout << "    generating blurred image" << endl;

	Box2i dw1 = iptr1->dataWindow();
	int sof1 = CubeMap::sizeOfFace (dw1);

	Box2i dw2 (V2i (0, 0), V2i (OUT_WIDTH - 1, OUT_WIDTH * 6 - 1));
	int sof2 = CubeMap::sizeOfFace (dw2);

	iptr2->resize (ENVMAP_CUBE, dw2);
	iptr2->clear ();

	Array2D<Rgba> &pixels1 = iptr1->pixels();
	Array2D<Rgba> &pixels2 = iptr2->pixels();

	for (int f2 = CUBEFACE_POS_X; f2 <= CUBEFACE_NEG_Z; ++f2)
	{
	    if (verbose)
		cout << "        face " << f2 << endl;

	    CubeMapFace face2 = CubeMapFace (f2);

	    for (int y2 = 0; y2 < sof2; ++y2)
	    {
		for (int x2 = 0; x2 < sof2; ++x2)
		{
		    V2f posInFace2 (x2, y2);

		    V3f dir2 = CubeMap::direction
			(face2, dw2, posInFace2);
			
		    V2f pos2 = CubeMap::pixelPosition
			(face2, dw2, posInFace2);
		    
		    double weightTotal = 0;
		    double rTotal = 0;
		    double gTotal = 0;
		    double bTotal = 0;
		    double aTotal = 0;

		    Rgba &pixel2 =
			pixels2[toInt (pos2.y)][toInt (pos2.x)];

		    for (int f1 = CUBEFACE_POS_X; f1 <= CUBEFACE_NEG_Z; ++f1)
		    {
			CubeMapFace face1 = CubeMapFace (f1);

			for (int y1 = 0; y1 < sof1; ++y1)
			{
			    for (int x1 = 0; x1 < sof1; ++x1)
			    {
				V2f posInFace1 (x1, y1);

				V3f dir1 = CubeMap::direction
				    (face1, dw1, posInFace1);
				    
				V2f pos1 = CubeMap::pixelPosition
				    (face1, dw1, posInFace1);
				
				double weight = dir1 ^ dir2;

				if (weight <= 0)
				    continue;

				Rgba &pixel1 =
				    pixels1[toInt (pos1.y)][toInt (pos1.x)];

				weightTotal += weight;
				rTotal += pixel1.r * weight;
				gTotal += pixel1.g * weight;
				bTotal += pixel1.b * weight;
				aTotal += pixel1.a * weight;
			    }
			}
		    }

		    pixel2.r = rTotal / weightTotal;
		    pixel2.g = gTotal / weightTotal;
		    pixel2.b = bTotal / weightTotal;
		    pixel2.a = aTotal / weightTotal;
		}
	    }
	}

	swap (iptr1, iptr2);
    } 

    //
    // Depending on how many times we've re-sampled the image,
    // the result is now either in image1 or in image2.
    // If necessary, copy the result into image1.
    //

    if (iptr1 != &image1)
    {
	if (verbose)
	    cout << "    copying" << endl;

	Box2i dw = iptr1->dataWindow();
	image1.resize (ENVMAP_CUBE, dw);

	int w = dw.max.x - dw.min.x + 1;
	int h = dw.max.y - dw.min.y + 1;
	size_t size = w * h * sizeof (Rgba);

	memcpy (&image1.pixels()[0][0], &iptr1->pixels()[0][0], size);
    }
}