karbon

vflattencmd.cc

00001 /* This file is part of the KDE project
00002    Copyright (C) 2002, 2003 The Karbon Developers
00003 
00004    This library is free software; you can redistribute it and/or
00005    modify it under the terms of the GNU Library General Public
00006    License as published by the Free Software Foundation; either
00007    version 2 of the License, or (at your option) any later version.
00008 
00009    This library is distributed in the hope that it will be useful,
00010    but WITHOUT ANY WARRANTY; without even the implied warranty of
00011    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00012    Library General Public License for more details.
00013 
00014    You should have received a copy of the GNU Library General Public License
00015    along with this library; see the file COPYING.LIB.  If not, write to
00016    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
00017  * Boston, MA 02110-1301, USA.
00018 */
00019 
00020 #include "vflattencmd.h"
00021 #include <klocale.h>
00022 
00023 #include <core/vpath.h>
00024 #include <core/vsegment.h>
00025 
00026 // TODO: Think about if we want to adapt this:
00027 
00028 /*
00029  * <cite from GNU ghostscript's gxpflat.c>
00030  *
00031  * To calculate how many points to sample along a path in order to
00032  * approximate it to the desired degree of flatness, we define
00033  *      dist((x,y)) = abs(x) + abs(y);
00034  * then the number of points we need is
00035  *      N = 1 + sqrt(3/4 * D / flatness),
00036  * where
00037  *      D = max(dist(p0 - 2*p1 + p2), dist(p1 - 2*p2 + p3)).
00038  * Since we are going to use a power of 2 for the number of intervals,
00039  * we can avoid the square root by letting
00040  *      N = 1 + 2^(ceiling(log2(3/4 * D / flatness) / 2)).
00041  * (Reference: DEC Paris Research Laboratory report #1, May 1989.)
00042  *
00043  * We treat two cases specially.  First, if the curve is very
00044  * short, we halve the flatness, to avoid turning short shallow curves
00045  * into short straight lines.  Second, if the curve forms part of a
00046  * character (indicated by flatness = 0), we let
00047  *      N = 1 + 2 * max(abs(x3-x0), abs(y3-y0)).
00048  * This is probably too conservative, but it produces good results.
00049  *
00050  * </cite from GNU ghostscript's gxpflat.c>
00051  */
00052 
00053 
00054 VFlattenCmd::VFlattenCmd( VDocument *doc, double flatness )
00055     : VReplacingCmd( doc, i18n( "Flatten Curves" ) )
00056 {
00057     m_flatness = flatness > 0.0 ? flatness : 1.0;
00058 }
00059 
00060 void
00061 VFlattenCmd::visitVSubpath( VSubpath& path )
00062 {
00063     path.first();
00064 
00065     // Ommit first segment.
00066     while( path.next() )
00067     {
00068         while( !path.current()->isFlat( m_flatness )  )
00069         {
00070             // Split at midpoint.
00071             path.insert(
00072                 path.current()->splitAt( 0.5 ) );
00073         }
00074 
00075         // Convert to line.
00076         path.current()->setDegree( 1 );
00077 
00078         if( !success() )
00079             setSuccess();
00080     }
00081 }
00082 
KDE Home | KDE Accessibility Home | Description of Access Keys