/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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*
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#ifndef INCLUDED_BASEBMP_CLIPPEDLINERENDERER_HXX
#define INCLUDED_BASEBMP_CLIPPEDLINERENDERER_HXX
#include <basegfx/tools/rectcliptools.hxx>
#include <basegfx/point/b2ipoint.hxx>
#include <basegfx/range/b2ibox.hxx>
#include <vigra/diff2d.hxx>
#include <vigra/iteratortraits.hxx>
namespace basebmp
{
// factored-out bresenham setup code, which is used from two different
// places in renderClippedLine() below. Admittedly messy for the long
// parameter list...
inline bool prepareClip( sal_Int32 a1,
sal_Int32 a2,
sal_Int32 b1,
sal_Int32 da,
sal_Int32 db,
sal_Int32& o_as,
sal_Int32& o_bs,
int sa,
int sb,
sal_Int32& io_rem,
int& o_n,
sal_uInt32 clipCode1,
sal_uInt32 clipCount1,
sal_uInt32 clipCode2,
sal_uInt32 clipCount2,
sal_Int32 aMin,
sal_uInt32 aMinFlag,
sal_Int32 aMax,
sal_uInt32 aMaxFlag,
sal_Int32 bMin,
sal_uInt32 bMinFlag,
sal_Int32 bMax,
sal_uInt32 bMaxFlag,
bool bRoundTowardsPt2,
bool& o_bUseAlternateBresenham )
{
int ca(0), cb(0);
if( clipCode1 )
{
if( clipCode1 & aMinFlag )
{
ca = 2*db*(aMin - a1);
o_as = aMin;
}
else if( clipCode1 & aMaxFlag )
{
ca = 2*db*(a1 - aMax);
o_as = aMax;
}
if( clipCode1 & bMinFlag )
{
cb = 2*da*(bMin - b1);
o_bs = bMin;
}
else if( clipCode1 & bMaxFlag )
{
cb = 2*da*(b1 - bMax);
o_bs = bMax;
}
if( clipCount1 == 2 )
clipCode1 &= (ca + da < cb + int(!bRoundTowardsPt2)) ? ~(aMinFlag|aMaxFlag) : ~(bMinFlag|bMaxFlag);
if( clipCode1 & (aMinFlag|aMaxFlag) )
{
sal_Int32 da2 = 2*da;
if (da2 == 0)
return false; // overflow
cb = (ca + da - int(!bRoundTowardsPt2)) / (da2);
if( sb >= 0 )
{
o_bs = b1 + cb;
if( o_bs > bMax )
return false; // fully clipped
}
else
{
o_bs = b1 - cb;
if( o_bs < bMin )
return false; // fully clipped
}
io_rem += ca - da2*cb;
}
else
{
sal_Int32 db2 = 2*db;
if (db2 == 0)
return false; // overflow
ca = (cb - da + db2 - int(bRoundTowardsPt2)) / (db2);
if( sa >= 0 )
{
o_as = a1 + ca;
if( o_as > aMax )
return false; // fully clipped
}
else
{
o_as = a1 - ca;
if( o_as < aMin )
return false; // fully clipped
}
io_rem += db2*ca - cb;
}
}
else
{
o_as = a1; o_bs = b1;
}
if( clipCode2 )
{
if( clipCount2 == 2 )
{
ca = 2*db*((clipCode2 & aMinFlag) ? a1 - aMin : aMax - a1);
cb = 2*da*((clipCode2 & bMinFlag) ? b1 - bMin : bMax - b1);
clipCode2 &= (cb + da < ca + int(bRoundTowardsPt2)) ? ~(aMinFlag|aMaxFlag) : ~(bMinFlag|bMaxFlag);
}
if( clipCode2 & (aMinFlag|aMaxFlag) )
o_n = (clipCode2 & aMinFlag) ? o_as - aMin : aMax - o_as;
else
{
o_n = (clipCode2 & bMinFlag) ? o_bs - bMin : bMax - o_bs;
o_bUseAlternateBresenham = true;
}
}
else
o_n = (a2 >= o_as) ? a2 - o_as : o_as - a2;
return true; // at least one pixel to render
}
/** Render line to image iterators, clip against given rectangle
This method renders a line from aPt1 to aPt2, clipped against
rClipRect (the clipping will take place pixel-perfect, i.e. as if
the original bresenham-rendered line would have been clipped each
pixel individually. No slight shifts compared to unclipped lines).
@param aPt1
Start point of the line
@param aPt2
End point of the line
@param rClipRect
Rectangle to clip against
@param color
Color value to render the line with
@param begin
left-top image iterator
@param end
right-bottom image iterator
@param acc
Image accessor
@param bRoundTowardsPt2
Rounding mode to use. Giving false here results in line pixel tend
towards pt1, i.e. when a pixel exactly hits the middle between two
pixel, the pixel closer to pt1 will be chosen. Giving true here
makes renderClippedLine() choose pt2 in those cases.
*/
template< class Iterator, class Accessor >
void renderClippedLine( basegfx::B2IPoint aPt1,
basegfx::B2IPoint aPt2,
const basegfx::B2IBox& rClipRect,
typename Accessor::value_type color,
Iterator begin,
Accessor acc,
bool bRoundTowardsPt2=false )
{
// Algorithm according to Steven Eker's 'Pixel-perfect line clipping',
// Graphics Gems V, pp. 314-322
sal_uInt32 clipCode1 = basegfx::tools::getCohenSutherlandClipFlags(aPt1,
rClipRect);
sal_uInt32 clipCode2 = basegfx::tools::getCohenSutherlandClipFlags(aPt2,
rClipRect);
if( clipCode1 & clipCode2 )
return; // line fully clipped away, both endpoints share a half-plane
sal_uInt32 clipCount1 = basegfx::tools::getNumberOfClipPlanes(clipCode1);
sal_uInt32 clipCount2 = basegfx::tools::getNumberOfClipPlanes(clipCode2);
if( (clipCode1 != 0 && clipCode2 == 0)
|| (clipCount1 == 2 && clipCount2 == 1) )
{
std::swap(clipCount2,clipCount1);
std::swap(clipCode2,clipCode1);
std::swap(aPt1,aPt2);
bRoundTowardsPt2 = !bRoundTowardsPt2;
}
const sal_Int32 x1 = aPt1.getX();
const sal_Int32 x2 = aPt2.getX();
const sal_Int32 y1 = aPt1.getY();
const sal_Int32 y2 = aPt2.getY();
// TODO(E1): This might overflow
sal_Int32 adx = x2 - x1;
int sx = 1;
if( adx < 0 )
{
adx *= -1;
sx = -1;
}
// TODO(E1): This might overflow
sal_Int32 ady = y2 - y1;
int sy = 1;
if( ady < 0 )
{
ady *= -1;
sy = -1;
}
int n = 0;
sal_Int32 xs = x1;
sal_Int32 ys = y1;
bool bUseAlternateBresenham=false;
sal_Int32 nMinY(rClipRect.getMinY());
sal_Int32 nMaxY(rClipRect.getMaxY()-1);
sal_Int32 nMinX(rClipRect.getMinX());
sal_Int32 nMaxX(rClipRect.getMaxX()-1);
if( adx >= ady )
{
// semi-horizontal line
sal_Int32 rem = 2*ady - adx - int(!bRoundTowardsPt2);
if( !prepareClip(x1, x2, y1, adx, ady, xs, ys, sx, sy,
rem, n, clipCode1, clipCount1, clipCode2, clipCount2,
nMinX, basegfx::tools::RectClipFlags::LEFT,
nMaxX, basegfx::tools::RectClipFlags::RIGHT,
nMinY, basegfx::tools::RectClipFlags::TOP,
nMaxY, basegfx::tools::RectClipFlags::BOTTOM,
bRoundTowardsPt2, bUseAlternateBresenham ) )
return; // line fully clipped away, no active pixel inside rect
Iterator currIter( begin + vigra::Diff2D(0,ys) );
typename vigra::IteratorTraits<Iterator>::row_iterator
rowIter( currIter.rowIterator() + xs );
adx *= 2;
ady *= 2;
if( bUseAlternateBresenham )
{
if (rem < 0 && ady <= 0)
return; //break will never be hit under these circumstances
while(true)
{
if (xs >= nMinX && xs <= nMaxX && ys >= nMinY && ys <= nMaxY)
acc.set(color, rowIter);
if( rem >= 0 )
{
// this is intended - we clip endpoint against y
// plane, so n here denotes y range to render
if( --n < 0 )
break;
ys += sy;
xs += sx;
rem -= adx;
currIter.y += sy;
rowIter = currIter.rowIterator() + xs;
}
else
{
xs += sx;
rowIter += sx;
}
rem += ady;
}
}
else
{
while(true)
{
if (xs >= nMinX && xs <= nMaxX && ys >= nMinY && ys <= nMaxY)
acc.set(color, rowIter);
if( --n < 0 )
break;
if( rem >= 0 )
{
ys += sy;
xs += sx;
rem -= adx;
currIter.y += sy;
rowIter = currIter.rowIterator() + xs;
}
else
{
xs += sx;
rowIter += sx;
}
rem += ady;
}
}
}
else
{
// semi-vertical line
sal_Int32 rem = 2*adx - ady - int(!bRoundTowardsPt2);
if( !prepareClip(y1, y2, x1, ady, adx, ys, xs, sy, sx,
rem, n, clipCode1, clipCount1, clipCode2, clipCount2,
nMinY, basegfx::tools::RectClipFlags::TOP,
nMaxY, basegfx::tools::RectClipFlags::BOTTOM,
nMinX, basegfx::tools::RectClipFlags::LEFT,
nMaxY, basegfx::tools::RectClipFlags::RIGHT,
bRoundTowardsPt2, bUseAlternateBresenham ) )
return; // line fully clipped away, no active pixel inside rect
Iterator currIter( begin + vigra::Diff2D(xs,0) );
typename vigra::IteratorTraits<Iterator>::column_iterator
colIter( currIter.columnIterator() + ys );
adx *= 2;
ady *= 2;
if( bUseAlternateBresenham )
{
if (rem < 0 && adx <= 0)
return; //break will never be hit under these circumstances
while(true)
{
if (xs >= nMinX && xs <= nMaxX && ys >= nMinY && ys <= nMaxY)
acc.set(color, colIter);
if( rem >= 0 )
{
// this is intended - we clip endpoint against x
// plane, so n here denotes x range to render
if( --n < 0 )
break;
xs += sx;
ys += sy;
rem -= ady;
currIter.x += sx;
colIter = currIter.columnIterator() + ys;
}
else
{
ys += sy;
colIter += sy;
}
rem += adx;
}
}
else
{
while(true)
{
if (xs >= nMinX && xs <= nMaxX && ys >= nMinY && ys <= nMaxY)
acc.set(color, colIter);
if( --n < 0 )
break;
if( rem >= 0 )
{
xs += sx;
ys += sy;
rem -= ady;
currIter.x += sx;
colIter = currIter.columnIterator() + ys;
}
else
{
ys += sy;
colIter += sy;
}
rem += adx;
}
}
}
}
} // namespace basebmp
#endif /* INCLUDED_BASEBMP_CLIPPEDLINERENDERER_HXX */
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */