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/****************************************************************************
Xplanet 0.94 - render an image of a planet into an X window
Copyright (C) 2002 Hari Nair <hari@alumni.caltech.edu>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
****************************************************************************/
#include "Location.h"
#include "Options.h"
#include "util.h"
#include "xplanet.h"
#include "libprojection.h"
void
getColor(const ProjectionRectangular *image_rect,
const double lon, const double lat, const double darkening,
unsigned char pixel[3])
{
if (opts.blend == 0)
{
int ilon, ilat;
if (image_rect->sphericalToPixel(lon, lat, ilon, ilat))
{
int ipos = 3 * (ilat*image_rect->getWidth() + ilon);
for (int i = 0; i < 3; i++)
pixel[i] = (unsigned char) (darkening
* image_rect->rgb_data[ipos++]);
}
else
{
memset(pixel, 0, 3);
}
return;
}
/*
The point (lon, lat) falls into one of these four pixels. The
color returned will be an area weighted average of these four.
--- ---
| 0 | 1 |
--- ---
| 2 | 3 |
--- ---
*/
int ix[4], iy[4];
if (!image_rect->sphericalToPixel(lon, lat, ix[1], iy[2]))
{
memset(pixel, 0, 3);
return;
}
if (ix[1] == 0)
{
ix[0] = image_rect->getWidth() - 1;
ix[1] = 0;
}
else
{
ix[0] = ix[1] - 1;
}
iy[0] = iy[2] - 1;
if (iy[0] == -1) iy[0] = 0;
ix[2] = ix[0];
ix[3] = ix[1];
iy[1] = iy[0];
iy[3] = iy[2];
double t = lon - image_rect->xToLon(ix[2]);
if (t > M_PI) t -= TWO_PI;
if (t < -M_PI) t += TWO_PI;
t /= image_rect->getDeltaLon();
double u = ((lat - image_rect->yToLat(iy[2]))
/ image_rect->getDeltaLat());
// Weights are from Numerical Recipes, 2nd Edition
// weight[0] = (1 - t) * u;
// weight[2] = (1-t) * (1-u);
// weight[3] = t * (1-u);
double weight[4];
weight[1] = t * u;
weight[0] = u - weight[1];
weight[2] = 1 - t - u + weight[1];
weight[3] = t - weight[1];
memset(pixel, 0, 3);
for (int ii = 0; ii < 4; ii++)
{
int ipos = 3*(iy[ii]*image_rect->getWidth() + ix[ii]);
weight[ii] *= darkening;
for (int jj = 0; jj < 3; jj++)
{
pixel[jj] += (unsigned char)
(weight[ii] * image_rect->rgb_data[ipos++]);
}
}
}
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