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authorNorbert Preining <norbert@preining.info>2019-09-02 13:46:59 +0900
committerNorbert Preining <norbert@preining.info>2019-09-02 13:46:59 +0900
commite0c6872cf40896c7be36b11dcc744620f10adf1d (patch)
tree60335e10d2f4354b0674ec22d7b53f0f8abee672 /graphics/epix/Color_Utils.cc
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+/*
+ * Color_Utils.cc -- Functions for manipulating color densities
+ * These functions are not normally available to users.
+ *
+ * This file is part of ePiX, a C++ library for creating high-quality
+ * figures in LaTeX
+ *
+ * Version 1.1.17
+ *
+ * Last Change: September 14, 2007
+ */
+
+/*
+ * Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006
+ * Andrew D. Hwang <rot 13 nujnat at zngupf dot ubylpebff dot rqh>
+ * Department of Mathematics and Computer Science
+ * College of the Holy Cross
+ * Worcester, MA, 01610-2395, USA
+ *
+ */
+
+/*
+ * ePiX 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.
+ *
+ * ePiX 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 ePiX; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+#include <sstream>
+#include <cmath>
+
+// #include "constants.h"
+// #include "functions.h"
+
+#include "Color_Utils.h"
+
+namespace ePiX {
+
+ // Magic number: 8-bits per color channel
+ const int COLORS(0xFF);
+
+ // Force double to [0,1]
+ double clip_to_unit(double t)
+ {
+ if (t < 0) return 0;
+ else if (t > 1) return 1;
+ else return t;
+ }
+
+ double rd(double arg) // may assume arg in [0,1]
+ {
+ return floor(COLORS*arg)/COLORS; // round down to nearest 8-bit
+ }
+
+ // represent a double in [0,1] by an 8-bit hex string
+ std::string dtohex(double arg) // assumes arg>0
+ {
+ using std::ios_base;
+ int dens((int) floor(arg*COLORS));
+
+ std::ostringstream value;
+ value.setf(ios_base::hex, ios_base::basefield);
+
+ if (dens <= 0xF) // pad
+ value << "0";
+
+ value << dens;
+ return value.str();
+ }
+
+ // saw2th:R -> [-2,2] is (1) a sawtooth function; (2) the identity on [-2,2]
+ double saw2th(double x)
+ {
+ return x - 4*floor((x+2)/4);
+ }
+
+ /*
+ * clippy(x):
+ * 1.... ____ if (x >= 0)
+ * .\ /. . return x <= 1 ? x : 1;
+ * . \ / . .
+ * 0......\____/ . . else
+ * -2 -1 0 1 2 --> x return x >= -1 ? 0 : -1-x;
+ */
+ double clippy(double x)
+ {
+ x = saw2th(x);
+ return (x >= 0) ? ( x <= 1 ? x : 1 ) : ( x >= -1 ? 0 : -1-x );
+ }
+
+ double make_r(double r, double g, double b)
+ {
+ return clip_to_unit(clippy( r) + clippy(-g) + clippy(-b));
+ }
+
+ double make_g(double r, double g, double b)
+ {
+ return clip_to_unit(clippy(-r) + clippy( g) + clippy(-b));
+ }
+
+ double make_b(double r, double g, double b)
+ {
+ return clip_to_unit(clippy(-r) + clippy(-g) + clippy( b));
+ }
+} // end of namespace