void
resizeLatLong (const EnvmapImage &image1,
EnvmapImage &image2,
const Box2i &image2DataWindow,
float filterRadius,
int numSamples)
{
int w = image2DataWindow.max.x - image2DataWindow.min.x + 1;
int h = image2DataWindow.max.y - image2DataWindow.min.y + 1;
float radius = 0.5f * 2 * M_PI * filterRadius / w;
image2.resize (ENVMAP_LATLONG, image2DataWindow);
image2.clear ();
Array2D<Rgba> &pixels = image2.pixels();
for (int y = 0; y < h; ++y)
{
for (int x = 0; x < w; ++x)
{
V3f dir = LatLongMap::direction (image2DataWindow, V2f (x, y));
pixels[y][x] = image1.filteredLookup (dir, radius, numSamples);
}
}
}
void
resizeCube (const EnvmapImage &image1,
EnvmapImage &image2,
const Box2i &image2DataWindow,
float filterRadius,
int numSamples)
{
if (image1.type() == ENVMAP_CUBE && image1.dataWindow() == image2DataWindow)
{
//
// Special case - the input image is a cube-face environment
// map with the same size as the output image. We can copy
// the input image without resampling.
//
image2.resize (ENVMAP_CUBE, image2DataWindow);
int w = image2DataWindow.max.x - image2DataWindow.min.x + 1;
int h = image2DataWindow.max.y - image2DataWindow.min.y + 1;
memcpy (&(image2.pixels()[0][0]),
&(image1.pixels()[0][0]),
sizeof (Rgba) * w * h);
return;
}
//
// Resampe the input image
//
int sof = CubeMap::sizeOfFace (image2DataWindow);
float radius = 1.5f * filterRadius / sof;
image2.resize (ENVMAP_CUBE, image2DataWindow);
image2.clear ();
Array2D<Rgba> &pixels = image2.pixels();
for (int f = CUBEFACE_POS_X; f <= CUBEFACE_NEG_Z; ++f)
{
CubeMapFace face = CubeMapFace (f);
for (int y = 0; y < sof; ++y)
{
for (int x = 0; x < sof; ++x)
{
V2f posInFace (x, y);
V3f dir =
CubeMap::direction (face, image2DataWindow, posInFace);
V2f pos =
CubeMap::pixelPosition (face, image2DataWindow, posInFace);
pixels[int (pos.y + 0.5f)][int (pos.x + 0.5f)] =
image1.filteredLookup (dir, radius, numSamples);
}
}
}
}
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);
}
}