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[asimage] Make the two ellipse fill spans mirror each other #23133

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Merged
linev merged 1 commit into from
Aug 25, 2026
+11 −127
Merged

[asimage] Make the two ellipse fill spans mirror each other #23133

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6 changes: 4 additions & 2 deletions builtins/libAfterImage/draw.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1523,6 +1523,7 @@ asim_ellips2( ASDrawContext *ctx, int x, int y, int rx, int ry, int angle, Bool
{
double d ;
int dx1 = 0, dx2 = 0 ;
int fill_edge = -1 ;
d = A*(double)x1*(double)x1 + BB +CC*(double)x1;
#ifdef DEBUG_ELLIPS
fprintf( stderr, "line = %d, d1 = %f", y-line, d );
Expand Down Expand Up @@ -1634,6 +1635,7 @@ asim_ellips2( ASDrawContext *ctx, int x, int y, int rx, int ry, int angle, Bool
dd += aa ;
}
x2 += (dx2>>1)-1 ;
fill_edge = 1 ;
last_med_dd2 = med_dd ;
}
}else if( line < yr )
Expand Down Expand Up @@ -1699,8 +1701,8 @@ asim_ellips2( ASDrawContext *ctx, int x, int y, int rx, int ry, int angle, Bool
#endif
if( fill )
{
CTX_FILL_HLINE(ctx,x+(x1-2),y-y1,x+x2-1,255);
CTX_FILL_HLINE(ctx,x-x2-1,y+y1,x-(x1-2),255);
CTX_FILL_HLINE(ctx,x+(x1-2),y-y1,x+(x2+fill_edge),255);
CTX_FILL_HLINE(ctx,x-(x2+fill_edge),y+y1,x-(x1-2),255);
}

CC -= 2.*C ;
Expand Down
3 changes: 0 additions & 3 deletions graf2d/asimage/test/CMakeLists.txt
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Expand Up @@ -5,6 +5,3 @@
# For the list of contributors see $ROOTSYS/README/CREDITS.

ROOT_ADD_GTEST(TASImageDraw tasimage_draw.cxx LIBRARIES ASImage)

# add failing test until fixed
ROOT_ADD_GTEST(TASImageDrawEllipse tasimage_ellipse_draw.cxx WILLFAIL LIBRARIES ASImage)
13 changes: 7 additions & 6 deletions graf2d/asimage/test/tasimage_draw.cxx
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Expand Up @@ -169,22 +169,24 @@ TEST(TASImage, FillePolygonLowAlpha)
CheckFilledShapeStaysInside("#100000FF", 2);
}

/*

// comment out all ellpse test while they are failing
// https://github.com/root-project/root/issues/23120
//
// asim_ellips2 walks a tilted ellipse one scanline pair at a time and exploits
// the 180 degree rotational symmetry, so the two spans it fills per iteration
// must mirror each other. The right edge was one pixel short of its partner,
// which left unfilled pixels along the tilted boundary. The point checked below
// sits inside the ellipse and used to stay empty.

TEST(TASImage, FilledEllipsOpaque)
{
CheckFilledShapeStaysInside("#FF2277CC", 3);
}

// Used to leak out of the circle and fill the whole image.
TEST(TASImage, FilledEllipsHighAlpha)
{
CheckFilledShapeStaysInside("#C02277CC", 3);
}

// Used to hang: the colour from the issue report.
TEST(TASImage, FilledEllipsSemiTransparent)
{
CheckFilledShapeStaysInside("#7F2277CC", 3);
Expand All @@ -194,4 +196,3 @@ TEST(TASImage, FilleEllipsLowAlpha)
{
CheckFilledShapeStaysInside("#102277CC", 3);
}
*/
116 changes: 0 additions & 116 deletions graf2d/asimage/test/tasimage_ellipse_draw.cxx
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