kicad/common/font/outline_decomposer.cpp

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/*
* This program source code file is part of KICAD, a free EDA CAD application.
*
* Copyright (C) 2021 Ola Rinta-Koski <gitlab@rinta-koski.net>
* Copyright (C) 2021 Kicad Developers, see AUTHORS.txt for contributors.
*
* Outline font class
*
* 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, you may find one here:
* http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
* or you may search the http://www.gnu.org website for the version 2 license,
* or you may write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
*/
#include <font/outline_decomposer.h>
#include <bezier_curves.h>
using namespace KIFONT;
OUTLINE_DECOMPOSER::OUTLINE_DECOMPOSER( FT_Outline& aOutline ) :
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m_outline( aOutline ),
m_contours( nullptr )
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{
}
static VECTOR2D toVector2D( const FT_Vector* aFreeTypeVector )
{
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return VECTOR2D( aFreeTypeVector->x * GLYPH_SIZE_SCALER,
aFreeTypeVector->y * GLYPH_SIZE_SCALER );
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}
void OUTLINE_DECOMPOSER::newContour()
{
CONTOUR contour;
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contour.m_Orientation = FT_Outline_Get_Orientation( &m_outline );
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m_contours->push_back( contour );
}
void OUTLINE_DECOMPOSER::addContourPoint( const VECTOR2D& p )
{
// don't add repeated points
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if( m_contours->back().m_Points.empty() || m_contours->back().m_Points.back() != p )
m_contours->back().m_Points.push_back( p );
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}
int OUTLINE_DECOMPOSER::moveTo( const FT_Vector* aEndPoint, void* aCallbackData )
{
OUTLINE_DECOMPOSER* decomposer = static_cast<OUTLINE_DECOMPOSER*>( aCallbackData );
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decomposer->m_lastEndPoint = toVector2D( aEndPoint );
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decomposer->newContour();
decomposer->addContourPoint( decomposer->m_lastEndPoint );
return 0;
}
int OUTLINE_DECOMPOSER::lineTo( const FT_Vector* aEndPoint, void* aCallbackData )
{
OUTLINE_DECOMPOSER* decomposer = static_cast<OUTLINE_DECOMPOSER*>( aCallbackData );
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decomposer->m_lastEndPoint = toVector2D( aEndPoint );
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decomposer->addContourPoint( decomposer->m_lastEndPoint );
return 0;
}
int OUTLINE_DECOMPOSER::quadraticTo( const FT_Vector* aControlPoint, const FT_Vector* aEndPoint,
void* aCallbackData )
{
return cubicTo( aControlPoint, nullptr, aEndPoint, aCallbackData );
}
int OUTLINE_DECOMPOSER::cubicTo( const FT_Vector* aFirstControlPoint,
const FT_Vector* aSecondControlPoint, const FT_Vector* aEndPoint,
void* aCallbackData )
{
OUTLINE_DECOMPOSER* decomposer = static_cast<OUTLINE_DECOMPOSER*>( aCallbackData );
GLYPH_POINTS bezier;
bezier.push_back( decomposer->m_lastEndPoint );
bezier.push_back( toVector2D( aFirstControlPoint ) );
if( aSecondControlPoint )
{
// aSecondControlPoint == nullptr for quadratic Beziers
bezier.push_back( toVector2D( aSecondControlPoint ) );
}
bezier.push_back( toVector2D( aEndPoint ) );
GLYPH_POINTS result;
decomposer->approximateBezierCurve( result, bezier );
for( const VECTOR2D& p : result )
decomposer->addContourPoint( p );
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decomposer->m_lastEndPoint = toVector2D( aEndPoint );
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return 0;
}
void OUTLINE_DECOMPOSER::OutlineToSegments( CONTOURS* aContours )
{
m_contours = aContours;
FT_Outline_Funcs callbacks;
callbacks.move_to = moveTo;
callbacks.line_to = lineTo;
callbacks.conic_to = quadraticTo;
callbacks.cubic_to = cubicTo;
callbacks.shift = 0;
callbacks.delta = 0;
FT_Error e = FT_Outline_Decompose( &m_outline, &callbacks, this );
if( e )
{
// TODO: handle error != 0
}
for( CONTOUR& c : *m_contours )
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c.m_Winding = winding( c.m_Points );
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}
// use converter in kimath
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bool OUTLINE_DECOMPOSER::approximateQuadraticBezierCurve( GLYPH_POINTS& aResult,
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const GLYPH_POINTS& aBezier ) const
{
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wxASSERT( aBezier.size() == 3 );
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// BEZIER_POLY only handles cubic Bezier curves, even though the
// comments say otherwise...
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//
// Quadratic to cubic Bezier conversion:
// cpn = Cubic Bezier control points (n = 0..3, 4 in total)
// qpn = Quadratic Bezier control points (n = 0..2, 3 in total)
// cp0 = qp0, cp1 = qp0 + 2/3 * (qp1 - qp0), cp2 = qp2 + 2/3 * (qp1 - qp2), cp3 = qp2
GLYPH_POINTS cubic;
cubic.reserve( 4 );
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cubic.push_back( aBezier[0] ); // cp0
cubic.push_back( aBezier[0] + ( ( aBezier[1] - aBezier[0] ) * 2 / 3 ) ); // cp1
cubic.push_back( aBezier[2] + ( ( aBezier[1] - aBezier[2] ) * 2 / 3 ) ); // cp2
cubic.push_back( aBezier[2] ); // cp3
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return approximateCubicBezierCurve( aResult, cubic );
}
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bool OUTLINE_DECOMPOSER::approximateCubicBezierCurve( GLYPH_POINTS& aResult,
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const GLYPH_POINTS& aCubicBezier ) const
{
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wxASSERT( aCubicBezier.size() == 4 );
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// minimumSegmentLength defines the "smoothness" of the
// curve-to-straight-segments conversion: the larger, the coarser
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// TODO: find out what the minimum segment length should really be!
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constexpr int minimumSegmentLength = 10;
BEZIER_POLY converter( aCubicBezier );
converter.GetPoly( aResult, minimumSegmentLength );
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return true;
}
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bool OUTLINE_DECOMPOSER::approximateBezierCurve( GLYPH_POINTS& aResult,
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const GLYPH_POINTS& aBezier ) const
{
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switch( aBezier.size() )
{
case 4: // cubic
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return approximateCubicBezierCurve( aResult, aBezier );
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break;
case 3: // quadratic
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return approximateQuadraticBezierCurve( aResult, aBezier );
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break;
default:
// error, only 3 and 4 are acceptable values
return false;
}
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}
int OUTLINE_DECOMPOSER::winding( const GLYPH_POINTS& aContour ) const
{
// -1 == counterclockwise, 1 == clockwise
const int cw = 1;
const int ccw = -1;
if( aContour.size() < 2 )
{
// zero or one points, so not a clockwise contour - in fact not a contour at all
//
// It could also be argued that a contour needs 3 extremum points at a minimum to be
// considered a proper contour (ie. a glyph (subpart) outline, or a hole)
return 0;
}
unsigned int i_lowest_vertex = 0;
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double lowest_y = std::numeric_limits<double>::max();
for( unsigned int i = 0; i < aContour.size(); i++ )
{
VECTOR2D p = aContour[i];
if( p.y < lowest_y )
{
i_lowest_vertex = i;
lowest_y = p.y;
// note: we should also check for p.y == lowest_y and then choose the point with
// leftmost.x, but as p.x is a double, equality is a dubious concept; however
// this should suffice in the general case
}
}
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unsigned int i_prev_vertex = ( i_lowest_vertex + aContour.size() - 1 ) % aContour.size();
unsigned int i_next_vertex = ( i_lowest_vertex + 1 ) % aContour.size();
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const VECTOR2D& lowest = aContour[i_lowest_vertex];
VECTOR2D prev( aContour[i_prev_vertex] );
while( prev == lowest )
{
if( i_prev_vertex == 0 )
i_prev_vertex = aContour.size() - 1;
else
i_prev_vertex--;
if( i_prev_vertex == i_lowest_vertex )
{
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// ERROR: degenerate contour (all points are colinear with equal Y coordinate)
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// TODO: signal error
// for now let's just return something at random
return cw;
}
prev = aContour[i_prev_vertex];
}
VECTOR2D next( aContour[i_next_vertex] );
while( next == lowest )
{
if( i_next_vertex == aContour.size() - 1 )
i_next_vertex = 0;
else
i_next_vertex++;
if( i_next_vertex == i_lowest_vertex )
{
// ERROR: degenerate contour (all points are equal)
// TODO: signal error
// for now let's just return something at random
return cw;
}
next = aContour[i_next_vertex];
}
// winding is figured out based on the angle between the lowest
// vertex and its neighbours
//
// prev.x < lowest.x && next.x > lowest.x -> ccw
//
// prev.x > lowest.x && next.x < lowest.x -> cw
//
// prev.x < lowest.x && next.x < lowest.x:
// ?
//
// prev.x > lowest.x && next.x > lowest.x:
// ?
//
if( prev.x < lowest.x && next.x > lowest.x )
return ccw;
if( prev.x > lowest.x && next.x < lowest.x )
return cw;
double prev_deltaX = prev.x - lowest.x;
double prev_deltaY = prev.y - lowest.y;
double next_deltaX = next.x - lowest.x;
double next_deltaY = next.y - lowest.y;
double prev_atan = atan2( prev_deltaY, prev_deltaX );
double next_atan = atan2( next_deltaY, next_deltaX );
if( prev_atan > next_atan )
return ccw;
else
return cw;
}