/* === S Y N F I G ========================================================= */
/*! \file blineconvert.cpp
** \brief Template File
**
** $Id$
**
** \legal
** Copyright (c) 2002-2005 Robert B. Quattlebaum Jr., Adrian Bentley
** Copyright (c) 2007 Chris Moore
**
** This package 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 package 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.
** \endlegal
*/
/* ========================================================================= */
/* === H E A D E R S ======================================================= */
#ifdef USING_PCH
# include "pch.h"
#else
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <synfig/general.h>
#include "blineconvert.h"
#include <vector>
#include <ETL/gaussian>
#include <ETL/hermite>
#include <ETL/clock>
#include <float.h>
#include <algorithm>
#include <cassert>
#include <synfigapp/localization.h>
#endif
/* === U S I N G =========================================================== */
using namespace std;
using namespace etl;
using namespace synfig;
/* === M A C R O S ========================================================= */
#define EPSILON (1e-10)
/* === G L O B A L S ======================================================= */
/* === P R O C E D U R E S ================================================= */
/* === M E T H O D S ======================================================= */
//Derivative Functions for numerical approximation
//bias == 0 will get F' at f3, bias < 0 will get F' at f1, and bias > 0 will get F' at f5
template < class T >
inline void FivePointdt(T &df, const T &f1, const T &f2, const T &f3, const T &f4, const T &f5, int bias)
{
if (bias == 0) // middle
df = (f1 - f2*8 + f4*8 - f5)*(1/12.0f);
else if (bias < 0) // left
df = (-f1*25 + f2*48 - f3*36 + f4*16 - f5*3)*(1/12.0f);
else // right
df = (f1*3 - f2*16 + f3*36 - f4*48 + f5*25)*(1/12.0f);
}
template < class T >
inline void ThreePointdt(T &df, const T &f1, const T &f2, const T &f3, int bias)
{
if (bias == 0) // middle
df = (-f1 + f3)*(1/2.0f);
else if (bias < 0) // left
df = (-f1*3 + f2*4 - f3)*(1/2.0f);
else // right
df = (f1 - f2*4 + f3*3)*(1/2.0f);
}
// template < class T >
// inline void ThreePointddt(T &df, const T &f1, const T &f2, const T &f3, int bias)
// {
// // a 3 point approximation pretends to have constant acceleration,
// // so only one algorithm needed for left, middle, or right
// df = (f1 -f2*2 + f3)*(1/2.0f);
// }
//
// // WARNING -- totally broken
// template < class T >
// inline void FivePointddt(T &df, const T &f1, const T &f2, const T &f3, int bias)
// {
// if(bias == 0)
// {
// assert(0); // !?
// //middle
// //df = (- f1 + f2*16 - f3*30 + f4*16 - f5)*(1/12.0f);
// }/*else if(bias < 0)
// {
// //left
// df = (f1*7 - f2*26*4 + f3*19*6 - f4*14*4 + f5*11)*(1/12.0f);
// }else
// {
// //right
// df = (f1*3 - f2*16 + f3*36 - f4*48 + f5*25)*(1/12.0f);
// }*/
// //side ones don't work, use 3 point
// }
//
// //implement an arbitrary derivative
// //dumb algorithm
// template < class T >
// void DerivativeApprox(T &df, const T f[], const Real t[], int npoints, int indexval)
// {
// /*
// Lj(x) = PI_i!=j (x - xi) / PI_i!=j (xj - xi)
//
// so Lj'(x) = SUM_k PI_i!=j|k (x - xi) / PI_i!=j (xj - xi)
// */
//
// unsigned int i,j,k,i0,i1;
//
// Real Lpj,mult,div,tj;
// Real tval = t[indexval];
//
// //sum k
// for(j=0;j<npoints;++j)
// {
// Lpj = 0;
// div = 1;
// tj = t[j];
//
// for(k=0;k<npoints;++k)
// {
// if(k != j) //because there is no summand for k == j, since that term is missing from the original equation
// {
// //summation for k
// for(i=0;i<npoints;++i)
// {
// if(i != k)
// {
// mult *= tval - t[i];
// }
// }
//
// Lpj += mult; //add into the summation
//
// //since the ks follow the exact pattern we need for the divisor (use that too)
// div *= tj - t[k];
// }
// }
//
// //get the actual coefficient
// Lpj /= div;
//
// //add it in to the equation
// df += f[j]*Lpj;
// }
// }
//END numerical derivatives
// template < class T >
// inline int sign(T f, T tol)
// {
// if(f < -tol) return -1;
// if(f > tol) return 1;
// return 0;
// }
void GetFirstDerivatives(const std::vector<synfig::Point> &f, unsigned int left, unsigned int right, char *out, unsigned int dfstride)
{
unsigned int current = left;
if(right - left < 2)
return;
else if(right - left == 2)
{
synfig::Vector v = f[left+1] - f[left];
//set both to the one we want
*(synfig::Vector*)out = v;
out += dfstride;
*(synfig::Vector*)out = v;
out += dfstride;
}
else if(right - left < 6/*5*/) //should use 3 point
{
//left then middle then right
ThreePointdt(*(synfig::Vector*)out,f[left+0], f[left+1], f[left+2], -1);
current++;
out += dfstride;
for(;current < right-1; current++, out += dfstride)
ThreePointdt(*(synfig::Vector*)out,f[current-1], f[current], f[current+1], 0);
ThreePointdt(*(synfig::Vector*)out,f[right-3], f[right-2], f[right-1], 1);
current++;
out += dfstride;
}else //can use 5 point
{
//left 2 then middle bunch then right two
//may want to use 3 point for inner edge ones
FivePointdt(*(synfig::Vector*)out,f[left+0], f[left+1], f[left+2], f[left+3], f[left+4], -2);
out += dfstride;
FivePointdt(*(synfig::Vector*)out,f[left+1], f[left+2], f[left+3], f[left+4], f[left+5], -1);
out += dfstride;
current += 2;
for(;current < right-2; current++, out += dfstride)
FivePointdt(*(synfig::Vector*)out,f[current-2], f[current-1], f[current], f[current+1], f[current+2], 0);
FivePointdt(*(synfig::Vector*)out,f[right-6], f[right-5], f[right-4], f[right-3], f[right-2], 2);
out += dfstride;
FivePointdt(*(synfig::Vector*)out,f[right-5], f[right-4], f[right-3], f[right-2], f[right-1], 1);
out += dfstride;
current += 2;
}
}
void GetSimpleDerivatives(const std::vector<synfig::Point> &f, int left, int right,
std::vector<synfig::Point> &df, int outleft,
const std::vector<synfig::Real> &/*di*/)
{
int i1,i2,i;
int offset = 2; //df = 1/2 (f[i+o]-f[i-o])
assert((int)df.size() >= right-left+outleft); //must be big enough
for(i = left; i < right; ++i)
{
//right now indices (figure out distance later)
i1 = std::max(left,i-offset);
i2 = std::max(left,i+offset);
df[outleft++] = (f[i2] - f[i1])*0.5f;
}
}
//get the curve error from the double sample list of work points (hopefully that's enough)
Real CurveError(const synfig::Point *pts, unsigned int n, std::vector<synfig::Point> &work, int left, int right)
{
if(right-left < 2) return -1;
int i,j;
//get distances to each point
Real d,dtemp,dsum;
//synfig::Vector v,vt;
//synfig::Point p1,p2;
synfig::Point pi;
std::vector<synfig::Point>::const_iterator it;//,end = work.begin()+right;
//unsigned int size = work.size();
//for each line, get distance
d = 0; //starts at 0
for(i = 0; i < (int)n; ++i)
{
pi = pts[i];
dsum = FLT_MAX;
it = work.begin()+left;
//p2 = *it++; //put it at left+1
for(j = left/*+1*/; j < right; ++j,++it)
{
/*p1 = p2;
p2 = *it;
v = p2 - p1;
vt = pi - p1;
dtemp = v.mag_squared() > 1e-12 ? (vt*v)/v.mag_squared() : 0; //get the projected time value for the current line
//get distance to line segment with the time value clamped 0-1
if(dtemp >= 1) //use p+v
{
vt += v; //makes it pp - (p+v)
}else if(dtemp > 0) //use vt-proj
{
vt -= v*dtemp; // vt - proj_v(vt) //must normalize the projection vector to work
}
//else use p
dtemp = vt.mag_squared();*/
dtemp = (pi - *it).mag_squared();
if(dtemp < dsum)
dsum = dtemp;
}
//accumulate the points' min distance from the curve
d += sqrt(dsum);
}
return d;
}
typedef synfigapp::BLineConverter::cpindex cpindex;
//has the index data and the tangent scale data (relevant as it may be)
int tessellate_curves(const std::vector<cpindex> &inds, const std::vector<Point> &f, const std::vector<synfig::Vector> &df, std::vector<Point> &work)
{
if(inds.size() < 2)
return 0;
etl::hermite<Point> curve;
int ntess = 0;
std::vector<cpindex>::const_iterator j = inds.begin(),j2, end = inds.end();
unsigned int ibase = inds[0].curind;
j2 = j++;
for(; j != end; j2 = j++)
{
//if this curve has invalid error (in j) then retessellate its work points (requires reparametrization, etc.)
if(j->error < 0)
{
//get the stepsize etc. for the number of points in here
unsigned int n = j->curind - j2->curind + 1; //that's the number of points in the span
unsigned int k, kend, i0, i3;
//so reset the right chunk
Real t, dt = 1/(Real)(n*2-2); //assuming that they own only n points
//start at first intermediate
t = 0;
i0 = j2->curind; i3 = j->curind;
k = (i0-ibase)*2; //start on first intermediary point (2x+1)
kend = (i3-ibase)*2; //last point to set (not intermediary)
//build hermite curve, it's easier
curve.p1() = f[i0];
curve.p2() = f[i3];
curve.t1() = df[i0-ibase] * (df[i0-ibase].mag_squared() > 1e-4
? j2->tangentscale/df[i0-ibase].mag()
: j2->tangentscale);
curve.t2() = df[i3-ibase] * (df[i3-ibase].mag_squared() > 1e-4
? j->tangentscale/df[i3-ibase].mag()
: j->tangentscale);
curve.sync();
//MUST include the end point (since we are ignoring left one)
for(; k < kend; ++k, t += dt)
{
work[k] = curve(t);
}
work[k] = curve(1); //k == kend, t == 1 -> c(t) == p2
++ntess;
}
}
return ntess;
}
synfigapp::BLineConverter::BLineConverter()
{
pixelwidth = 1;
smoothness = 0.70f;
width = 0;
};
void
synfigapp::BLineConverter::clear()
{
point_cache.clear();
width_cache.clear();
ftemp.clear();
deriv.clear();
curvature.clear();
break_tangents.clear();
cum_dist.clear();
this_dist.clear();
work.clear();
curind.clear();
}
void
synfigapp::BLineConverter::operator()(std::list<synfig::BLinePoint> &blinepoints_out,
const std::list<synfig::Point> &points_in,
const std::list<synfig::Real> &widths_in)
{
//Profiling information
/*etl::clock::value_type initialprocess=0, curveval=0, breakeval=0, disteval=0;
etl::clock::value_type preproceval=0, tesseval=0, erroreval=0, spliteval=0;
unsigned int numpre=0, numtess=0, numerror=0, numsplit=0;
etl::clock_realtime timer,total;*/
//total.reset();
if (points_in.size() < 2)
return;
clear();
//removing digitization error harder than expected
//intended to fix little pen errors caused by the way people draw (tiny juts in opposite direction)
//Different solutions
// Average at both end points (will probably eliminate many points at each end of the samples)
// Average after the break points are found (weird points would still affect the curve)
// Just always get rid of breaks at the beginning and end if they are a certain distance apart
// This is will be current approach so all we do now is try to remove duplicate points
//remove duplicate points - very bad for fitting
//timer.reset();
{
std::list<synfig::Point>::const_iterator point_iter = points_in.begin(), end = points_in.end();
std::list<synfig::Real>::const_iterator width_iter = widths_in.begin();
synfig::Point c;
if (points_in.size() == widths_in.size())
{
for(bool first = true; point_iter != end; ++point_iter,++width_iter)
if (first || *point_iter != c) // eliminate duplicate points
{
first = false;
point_cache.push_back(c = *point_iter);
width_cache.push_back(*width_iter);
}
}
else
for(;point_iter != end; ++point_iter)
if(*point_iter != c) // eliminate duplicate points
point_cache.push_back(c = *point_iter);
}
//initialprocess = timer();
if (point_cache.size() < 7)
{
info("only %d unique points - giving up", point_cache.size());
return;
}
//get curvature information
//timer.reset();
{
int i_this, i_prev, i_next;
synfig::Vector v_prev, v_next;
curvature.resize(point_cache.size());
curvature.front() = curvature.back() = 1;
for (i_this = 1; i_this < (int)point_cache.size()-1; i_this++)
{
i_prev = std::max(0, i_this-2);
i_next = std::min((int)(point_cache.size()-1), i_this+2);
v_prev = point_cache[i_this] - point_cache[i_prev];
v_next = point_cache[i_next] - point_cache[i_this];
curvature[i_this] = (v_prev*v_next) / (v_prev.mag()*v_next.mag());
}
}
//curveval = timer();
//synfig::info("calculated curvature");
//find corner points and interpolate inside those
//timer.reset();
{
//break at sharp derivative points
//TODO tolerance should be set based upon digitization resolution (length dependent index selection)
Real tol = 0; //break tolerance, for the cosine of the change in angle (really high curvature or something)
unsigned int i = 0;
int sharpest_i=-1;
int last=0;
Real sharpest_curvature = 1;
break_tangents.push_back(0);
// loop through the curvatures; in each continuous run of
// curvatures that exceed the tolerance, find the one with the
// sharpest curvature and add its index to the list of indices
// at which to split tangents
for (i = 1; i < curvature.size()-1; ++i)
{
if (curvature[i] < tol)
{
if(curvature[i] < sharpest_curvature)
{
sharpest_curvature = curvature[i];
sharpest_i = i;
}
}
else if (sharpest_i > 0)
{
// don't have 2 corners too close to each other
if (sharpest_i >= last + 8) //! \todo make this configurable
{
//synfig::info("break: %d-%d",sharpest_i+1,curvature.size());
break_tangents.push_back(sharpest_i);
last = sharpest_i;
}
sharpest_i = -1;
sharpest_curvature = 1;
}
}
break_tangents.push_back(i);
// this section causes bug 1892566 if enabled
#if 1
//postprocess for breaks too close to each other
Real fixdistsq = 4*width*width; //the distance to ignore breaks at the end points (for fixing stuff)
Real d = 0;
Point p = point_cache[break_tangents.front()];
//first set
for (i = 1; i < break_tangents.size()-1; ++i) //do not want to include end point...
{
d = (point_cache[break_tangents[i]] - p).mag_squared();
if(d > fixdistsq) break; //don't want to group breaks if we ever get over the dist...
}
//want to erase all points before...
if(i != 1)
break_tangents.erase(break_tangents.begin(),break_tangents.begin()+i-1);
//end set
p = point_cache[break_tangents.back()];
for(i = break_tangents.size()-2; i > 0; --i) //start at one in from the end
{
d = (point_cache[break_tangents[i]] - p).mag_squared();
if(d > fixdistsq) break; //don't want to group breaks if we ever get over the dist
}
if(i != break_tangents.size()-2)
break_tangents.erase(break_tangents.begin()+i+2,break_tangents.end()); //erase all points that we found... found none if i has not advanced
//must not include the one we ended up on
#endif
}
//breakeval = timer();
//synfig::info("found break points: %d",break_tangents.size());
//get the distance calculation of the entire curve (for tangent scaling)
//timer.reset();
{
synfig::Point p1,p2;
p1=p2=point_cache[0];
cum_dist.resize(point_cache.size()); this_dist.resize(point_cache.size());
Real d = 0;
for(unsigned int i = 0; i < point_cache.size();)
{
d += (this_dist[i] = (p2-p1).mag());
cum_dist[i] = d;
p1=p2;
//! \todo is this legal? it reads off the end of the vector
p2=point_cache[++i];
}
}
//disteval = timer();
//synfig::info("calculated distance");
//now break at every point - calculate new derivatives each time
//TODO
//must be sure that the break points are 3 or more apart
//then must also store the breaks which are not smooth, etc.
//and figure out tangents between there
//for each pair of break points (as long as they are far enough apart) recursively subdivide stuff
//ignore the detected intermediate points
{
unsigned int i0=0,i3=0,is=0;
int i=0,j=0;
bool done = false;
Real errortol = smoothness*pixelwidth; //???? what should this value be
BLinePoint a;
synfig::Vector v;
//intemp = f; //don't want to smooth out the corners
bool breaktan = false, setwidth;
a.set_split_tangent_both(false);
//a.set_width(width);
a.set_width(1.0f);
setwidth = (point_cache.size() == width_cache.size());
for(j = 0; j < (int)break_tangents.size() - 1; ++j)
{
//for b[j] to b[j+1] subdivide and stuff
i0 = break_tangents[j];
i3 = break_tangents[j+1];
unsigned int size = i3-i0+1; //must include the end points
//new derivatives
//timer.reset();
ftemp.assign(point_cache.begin()+i0, point_cache.begin()+i3+1);
for(i=0;i<20;++i)
gaussian_blur_3(ftemp.begin(),ftemp.end(),false);
deriv.resize(size);
// Wondering whether the modification of the deriv vector
// using a char* pointer and pointer arithmetric was safe,
// I looked it up...
//
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2369.pdf tells me:
//
// 23.2.5 Class template vector [vector]
//
// [...] The elements of a vector are stored contiguously,
// meaning that if v is a vector<T,Allocator> where T is
// some type other than bool, then it obeys the identity
// &v[n] == &v[0] + n for all 0 <= n < v.size().
//
GetFirstDerivatives(ftemp,0,size,(char*)&deriv[0],sizeof(deriv[0]));
//GetSimpleDerivatives(ftemp,0,size,deriv,0,cum_dist);
//< don't have to worry about indexing stuff as it is all being taken care of right now
//preproceval += timer();
//numpre++;
work.resize(size*2-1); //guarantee that all points will be tessellated correctly (one point in between every 2 adjacent points)
//if size of work is size*2-1, the step size should be 1/(size*2 - 2)
//Real step = 1/(Real)(size*2 - 1);
//start off with break points as indices
curind.clear();
curind.push_back(cpindex(i0,cum_dist[i3]-cum_dist[i0],0)); //0 error because no curve on the left
curind.push_back(cpindex(i3,cum_dist[i3]-cum_dist[i0],-1)); //error needs to be reevaluated
done = false; //we want to loop
unsigned int dcount = 0;
//while there are still enough points between us, and the error is too high subdivide (and invalidate neighbors that share tangents)
while(!done)
{
//tessellate all curves with invalid error values
work[0] = point_cache[i0];
//timer.reset();
/*numtess += */tessellate_curves(curind,point_cache,deriv,work);
//tesseval += timer();
//now get all error values
//timer.reset();
for(i = 1; i < (int)curind.size(); ++i)
{
if(curind[i].error < 0) //must have been retessellated, so now recalculate error value
{
//evaluate error from points (starting at current index)
int size = curind[i].curind - curind[i-1].curind + 1;
curind[i].error = CurveError(&point_cache[curind[i-1].curind], size,
work,(curind[i-1].curind - i0)*2,(curind[i].curind - i0)*2+1);
/*if(curind[i].error > 1.0e5)
{
synfig::info("Holy crap %d-%d error %f",curind[i-1].curind,curind[i].curind,curind[i].error);
curind[i].error = -1;
numtess += tessellate_curves(curind,f,deriv,work);
curind[i].error = CurveError(&point_cache[curind[i-1].curind], size,
work,0,work.size());//(curind[i-1].curind - i0)*2,(curind[i].curind - i0)*2+1);
}*/
//numerror++;
}
}
//erroreval += timer();
//assume we're done
done = true;
//check each error to see if it's too big, if so, then subdivide etc.
int indsize = (int)curind.size();
Real maxrelerror = 0;
int maxi = -1;//, numpoints;
//timer.reset();
//get the maximum error and split there
for(i = 1; i < indsize; ++i)
{
//numpoints = curind[i].curind - curind[i-1].curind + 1;
if(curind[i].error > maxrelerror && curind[i].curind - curind[i-1].curind > 2) //only accept if it's valid
{
maxrelerror = curind[i].error;
maxi = i;
}
}
//split if error is too great
if(maxrelerror > errortol)
{
//add one to the left etc
unsigned int ibase = curind[maxi-1].curind, itop = curind[maxi].curind,
ibreak = (ibase + itop)/2;
Real scale, scale2;
assert(ibreak < point_cache.size());
//synfig::info("Split %d -%d- %d, error: %f", ibase,ibreak,itop,maxrelerror);
if(ibase != itop)
{
//invalidate current error of the changed tangents and add an extra segment
//enforce minimum tangents property
curind[maxi].error = -1;
curind[maxi-1].error = -1;
if(maxi+1 < indsize) curind[maxi+1].error = -1; //if there is a curve segment beyond this it will be effected as well
scale = cum_dist[itop] - cum_dist[ibreak];
scale2 = maxi+1 < indsize ? cum_dist[curind[maxi+1].curind] - cum_dist[itop] : scale; //to the right valid?
curind[maxi].tangentscale = std::min(scale, scale2);
scale = cum_dist[ibreak] - cum_dist[ibase];
scale2 = maxi >= 2 ? cum_dist[ibase] - cum_dist[curind[maxi-2].curind] : scale; // to the left valid -2 ?
curind[maxi-1].tangentscale = std::min(scale, scale2);
scale = std::min(cum_dist[ibreak] - cum_dist[ibase], cum_dist[itop] - cum_dist[ibreak]);
curind.insert(curind.begin()+maxi,cpindex(ibreak, scale, -1));
//curind.push_back(cpindex(ibreak, scale, -1));
//std::sort(curind.begin(), curind.end());
done = false;
//numsplit++;
}
}
//spliteval += timer();
dcount++;
}
//insert the last point too (just set tangent for now
is = curind[0].curind;
//first point inherits current tangent status
v = deriv[is - i0];
if(v.mag_squared() > EPSILON)
v *= (curind[0].tangentscale/v.mag());
if(!breaktan)
a.set_tangent(v);
else a.set_tangent2(v);
a.set_vertex(point_cache[is]);
if(setwidth)a.set_width(width_cache[is]);
blinepoints_out.push_back(a);
a.set_split_tangent_both(false); //won't need to break anymore
breaktan = false;
for(i = 1; i < (int)curind.size()-1; ++i)
{
is = curind[i].curind;
//first point inherits current tangent status
v = deriv[is-i0];
if(v.mag_squared() > EPSILON)
v *= (curind[i].tangentscale/v.mag());
a.set_tangent(v); // always inside, so guaranteed to be smooth
a.set_vertex(point_cache[is]);
if(setwidth)a.set_width(width_cache[is]);
blinepoints_out.push_back(a);
}
//set the last point's data
is = curind.back().curind; //should already be this
v = deriv[is-i0];
if(v.mag_squared() > EPSILON)
v *= (curind.back().tangentscale/v.mag());
a.set_tangent1(v);
a.set_split_tangent_both(true);
breaktan = true;
//will get the vertex and tangent 2 from next round
}
a.set_vertex(point_cache[i3]);
a.set_split_tangent_both(false);
if(setwidth)
a.set_width(width_cache[i3]);
blinepoints_out.push_back(a);
/*etl::clock::value_type totaltime = total(),
misctime = totaltime - initialprocess - curveval - breakeval - disteval
- preproceval - tesseval - erroreval - spliteval;
synfig::info(
"Curve Convert Profile:\n"
"\tInitial Preprocess: %f\n"
"\tCurvature Calculation: %f\n"
"\tBreak Calculation: %f\n"
"\tDistance Calculation: %f\n"
" Algorithm: (numtimes,totaltime)\n"
"\tPreprocess step: (%d,%f)\n"
"\tTessellation step: (%d,%f)\n"
"\tError step: (%d,%f)\n"
"\tSplit step: (%d,%f)\n"
" Num Input: %d, Num Output: %d\n"
" Total time: %f, Misc time: %f\n",
initialprocess, curveval,breakeval,disteval,
numpre,preproceval,numtess,tesseval,numerror,erroreval,numsplit,spliteval,
points_in.size(),blinepoints_out.size(),
totaltime,misctime);*/
return;
}
}
void synfigapp::BLineConverter::EnforceMinWidth(std::list<synfig::BLinePoint> &bline, synfig::Real min_pressure)
{
std::list<synfig::BLinePoint>::iterator i = bline.begin(),
end = bline.end();
for(i = bline.begin(); i != end; ++i)
if(i->get_width() < min_pressure)
i->set_width(min_pressure);
}