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sw_engine: fixed a antialiasing issue.

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Previously, a mechanism was introduced to skip antialiasing computations
when shapes are invisible due to their stroking. However, this mechanism
failed to account for the scale factor of the stroke; it only considered
the current stroke width as a threshold.

Consequently, when the stroke width is scaled up to a value smaller than
the threshold, the incorrect antialiasing approach is applied. This results
in the appearance of jagged edges.

The implemented fix rectifies this problem and ensures that the antialiasing
computation correctly takes into consideration both the visibility and the
scale factor of the stroke width.
This commit is contained in:
Hermet Park 2023-08-30 11:08:01 +09:00 • committed by Hermet Park
parent 09da0b86cb
commit 735c1cb9e4
1 changed files with 20 additions and 7 deletions
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27
src/renderer/sw_engine/tvgSwRenderer.cpp
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@ -78,6 +78,25 @@ struct SwShapeTask : SwTask
bool cmpStroking = false; bool cmpStroking = false;
bool clipper = false; bool clipper = false;
/* We assume that if the stroke width is greater than 2,
the shape's outline beneath the stroke could be adequately covered by the stroke drawing.
Therefore, antialiasing is disabled under this condition.
Additionally, the stroke style should not be dashed. */
bool antialiasing()
{
if (!rshape->stroke) return true;
auto width = rshape->stroke->width;
if (mathZero(width)) return true;
if (transform) {
if (transform->e11 > transform->e22) width *= transform->e11;
else width *= transform->e22;
}
return rshape->stroke->color[3] < 255 || width < 2.0f || rshape->stroke->dashCnt > 0 || rshape->stroke->strokeFirst;
}
bool clip(SwRleData* target) override bool clip(SwRleData* target) override
{ {
if (shape.fastTrack) rleClipRect(target, &bbox); if (shape.fastTrack) rleClipRect(target, &bbox);
@ -128,13 +147,7 @@ struct SwShapeTask : SwTask
//Fill //Fill
if (flags & (RenderUpdateFlag::Gradient | RenderUpdateFlag::Transform | RenderUpdateFlag::Color)) { if (flags & (RenderUpdateFlag::Gradient | RenderUpdateFlag::Transform | RenderUpdateFlag::Color)) {
if (visibleFill || clipper) { if (visibleFill || clipper) {
/* We assume that if stroke width is bigger than 2, if (!shapeGenRle(&shape, rshape, antialiasing())) goto err;
shape outline below stroke could be full covered by stroke drawing.
Thus it turns off antialising in that condition.
Also, it shouldn't be dash style. */
auto antiAlias = strokeAlpha < 255 || rshape->strokeWidth() <= 2 || rshape->strokeDash(nullptr, nullptr) > 0 || (rshape->stroke && rshape->stroke->strokeFirst);
if (!shapeGenRle(&shape, rshape, antiAlias)) goto err;
} }
if (auto fill = rshape->fill) { if (auto fill = rshape->fill) {
auto ctable = (flags & RenderUpdateFlag::Gradient) ? true : false; auto ctable = (flags & RenderUpdateFlag::Gradient) ? true : false;