/usr/share/doc/libplplot12/examples/c++/x30.cc is in libplplot-dev 5.10.0+dfsg-1.
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//
// Alpha color values demonstration.
//
// Copyright (C) 2008 Hazen Babcock
//
//
// This file is part of PLplot.
//
// PLplot is free software; you can redistribute it and/or modify
// it under the terms of the GNU Library General Public License as published
// by the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// PLplot 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 Library General Public License for more details.
//
// You should have received a copy of the GNU Library General Public License
// along with PLplot; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
//
// This example will only really be interesting when used with devices that
// support or alpha (or transparency) values, such as the cairo device family.
//
#include "plc++demos.h"
#ifdef PL_USE_NAMESPACE
using namespace std;
#endif
class x30 {
public:
x30( int, const char ** );
private:
plstream *pls;
static PLINT red[];
static PLINT green[];
static PLINT blue[];
static PLFLT alpha[];
static PLFLT px[];
static PLFLT py[];
static PLFLT pos[];
static PLFLT rcoord[];
static PLFLT gcoord[];
static PLFLT bcoord[];
static PLFLT acoord[];
static PLBOOL rev[];
};
PLINT x30::red[] = { 0, 255, 0, 0 };
PLINT x30::green[] = { 0, 0, 255, 0 };
PLINT x30::blue[] = { 0, 0, 0, 255 };
PLFLT x30::alpha[] = { 1.0, 1.0, 1.0, 1.0 };
PLFLT x30::px[] = { 0.1, 0.5, 0.5, 0.1 };
PLFLT x30::py[] = { 0.1, 0.1, 0.5, 0.5 };
PLFLT x30::pos[] = { 0.0, 1.0 };
PLFLT x30::rcoord[] = { 1.0, 1.0 };
PLFLT x30::gcoord[] = { 0.0, 0.0 };
PLFLT x30::bcoord[] = { 0.0, 0.0 };
PLFLT x30::acoord[] = { 0.0, 1.0 };
x30::x30( int argc, const char *argv[] )
{
int i, j;
PLINT icol, r, g, b;
PLFLT a;
pls = new plstream;
pls->parseopts( &argc, argv, PL_PARSE_FULL );
pls->init();
pls->scmap0n( 4 );
pls->scmap0a( red, green, blue, alpha, 4 );
//
// Page 1:
//
// This is a series of red, green and blue rectangles overlaid
// on each other with gradually increasing transparency.
//
// Set up the window
pls->adv( 0 );
pls->vpor( 0.0, 1.0, 0.0, 1.0 );
pls->wind( 0.0, 1.0, 0.0, 1.0 );
pls->col0( 0 );
pls->box( "", 1.0, 0, "", 1.0, 0 );
// Draw the boxes
for ( i = 0; i < 9; i++ )
{
icol = i % 3 + 1;
// Get a color, change its transparency and
// set it as the current color.
pls->gcol0a( icol, r, g, b, a );
pls->scol0a( icol, r, g, b, 1.0 - (double) i / 9.0 );
pls->col0( icol );
// Draw the rectangle
pls->fill( 4, px, py );
// Shift the rectangles coordinates
for ( j = 0; j < 4; j++ )
{
px[j] += 0.5 / 9.0;
py[j] += 0.5 / 9.0;
}
}
//
// Page 2:
//
// This is a bunch of boxes colored red, green or blue with a single
// large (red) box of linearly varying transparency overlaid. The
// overlaid box is completely transparent at the bottom and completely
// opaque at the top.
//
// Set up the window
pls->adv( 0 );
pls->vpor( 0.1, 0.9, 0.1, 0.9 );
pls->wind( 0.0, 1.0, 0.0, 1.0 );
// Draw the boxes. There are 25 of them drawn on a 5 x 5 grid.
for ( i = 0; i < 5; i++ )
{
// Set box X position
px[0] = 0.05 + 0.2 * i;
px[1] = px[0] + 0.1;
px[2] = px[1];
px[3] = px[0];
// We don't want the boxes to be transparent, so since we changed
// the colors transparencies in the first example we have to change
// the transparencies back to completely opaque.
icol = i % 3 + 1;
pls->gcol0a( icol, r, g, b, a );
pls->scol0a( icol, r, g, b, 1.0 );
pls->col0( icol );
for ( j = 0; j < 5; j++ )
{
// Set box y position and draw the box.
py[0] = 0.05 + 0.2 * j;
py[1] = py[0];
py[2] = py[0] + 0.1;
py[3] = py[2];
pls->fill( 4, px, py );
}
}
// Create the color map with 128 colors and use plscmap1la to initialize
// the color values with a linearly varying red transparency (or alpha)
pls->scmap1n( 128 );
pls->scmap1la( true, 2, pos, rcoord, gcoord, bcoord, acoord );
// Use that cmap1 to create a transparent red gradient for the whole
// window.
px[0] = 0.;
px[1] = 1.;
px[2] = 1.;
px[3] = 0.;
py[0] = 0.;
py[1] = 0.;
py[2] = 1.;
py[3] = 1.;
pls->gradient( 4, px, py, 90. );
delete pls;
}
int main( int argc, const char **argv )
{
x30 *x = new x30( argc, argv );
delete x;
}
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