Fix artifacts in distance field rendering due to bilerp
Because we were using the full distance field glyph rect, there were cases
when a neighboring texel might be set to full value (e.g. we might copy the
glyph over old data after a purge). This was giving artifacts, and insetting
the rect by 1 solves the problem. In doing this, I discovered that removing the
extra 1 texel pad around the glyph meant to handle bilerp, and insetting by 2,
works just as well and saves space in the glyph atlas.
R=bsalomon@google.com
Author: jvanverth@google.com
Review URL: https://codereview.chromium.org/239333002
git-svn-id: http://skia.googlecode.com/svn/trunk@14203 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/core/SkDistanceFieldGen.h b/src/core/SkDistanceFieldGen.h
index 756cff1..0510907 100644
--- a/src/core/SkDistanceFieldGen.h
+++ b/src/core/SkDistanceFieldGen.h
@@ -14,8 +14,9 @@
#define SK_DistanceFieldMagnitude 4
// we need to pad around the original glyph to allow our maximum distance of
// SK_DistanceFieldMagnitude texels away from any edge
-// we add one to this pad to allow for bilerp
-#define SK_DistanceFieldPad (SK_DistanceFieldMagnitude+1)
+#define SK_DistanceFieldPad 4
+// the rect we render with is inset from the distance field glyph size to allow for bilerp
+#define SK_DistanceFieldInset 2
// for the fragment shader
// The distance field is constructed as unsigned char values, so that the zero value is at 128,
diff --git a/src/gpu/GrDistanceFieldTextContext.cpp b/src/gpu/GrDistanceFieldTextContext.cpp
index 448e709..238bcca 100755
--- a/src/gpu/GrDistanceFieldTextContext.cpp
+++ b/src/gpu/GrDistanceFieldTextContext.cpp
@@ -14,6 +14,7 @@
#include "GrIndexBuffer.h"
#include "GrTextStrike.h"
#include "GrTextStrike_impl.h"
+#include "SkDistanceFieldGen.h"
#include "SkDraw.h"
#include "SkGpuDevice.h"
#include "SkPath.h"
@@ -295,10 +296,10 @@
SkASSERT(2*sizeof(SkPoint) == fDrawTarget->getDrawState().getVertexSize());
}
- SkScalar dx = SkIntToScalar(glyph->fBounds.fLeft);
- SkScalar dy = SkIntToScalar(glyph->fBounds.fTop);
- SkScalar width = SkIntToScalar(glyph->fBounds.width());
- SkScalar height = SkIntToScalar(glyph->fBounds.height());
+ SkScalar dx = SkIntToScalar(glyph->fBounds.fLeft + SK_DistanceFieldInset);
+ SkScalar dy = SkIntToScalar(glyph->fBounds.fTop + SK_DistanceFieldInset);
+ SkScalar width = SkIntToScalar(glyph->fBounds.width() - 2*SK_DistanceFieldInset);
+ SkScalar height = SkIntToScalar(glyph->fBounds.height() - 2*SK_DistanceFieldInset);
SkScalar scale = fTextRatio;
dx *= scale;
@@ -308,10 +309,10 @@
width *= scale;
height *= scale;
- SkFixed tx = SkIntToFixed(glyph->fAtlasLocation.fX);
- SkFixed ty = SkIntToFixed(glyph->fAtlasLocation.fY);
- SkFixed tw = SkIntToFixed(glyph->fBounds.width());
- SkFixed th = SkIntToFixed(glyph->fBounds.height());
+ SkFixed tx = SkIntToFixed(glyph->fAtlasLocation.fX + SK_DistanceFieldInset);
+ SkFixed ty = SkIntToFixed(glyph->fAtlasLocation.fY + SK_DistanceFieldInset);
+ SkFixed tw = SkIntToFixed(glyph->fBounds.width() - 2*SK_DistanceFieldInset);
+ SkFixed th = SkIntToFixed(glyph->fBounds.height() - 2*SK_DistanceFieldInset);
static const size_t kVertexSize = 2 * sizeof(SkPoint);
fVertices[2*fCurrVertex].setRectFan(sx,