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internal/stroke: fix point normalization for unit length.

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This fixes the cases where the unit length matches the hypotenuse.

Signed-off-by: Walter Werner SCHNEIDER <contact@schnwalter.eu>
This commit is contained in:
Walter Werner SCHNEIDER
2025-07-28 22:08:34 +03:00
committed by Elias Naur
parent 176570527d
commit 30f8ac10b7
2 changed files with 15 additions and 1 deletions
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internal/stroke/stroke.go
+5 -1
View File
@@ -342,7 +342,11 @@ func normPt(p f32.Point, l float32) f32.Point {
d := math.Hypot(float64(p.X), float64(p.Y))
l64 := float64(l)
if math.Abs(d-l64) < 1e-10 {
return f32.Point{}
if math.Signbit(float64(l)) {
return f32.Point{X: -p.X, Y: -p.Y}
} else {
return f32.Point{X: p.X, Y: p.Y}
}
}
n := float32(l64 / d)
return f32.Point{X: p.X * n, Y: p.Y * n}
internal/stroke/stroke_test.go
+10
View File
@@ -91,6 +91,16 @@ func TestNormPt(t *testing.T) {
{l: -20, ptIn: f32.Point{X: -20, Y: +20}, ptOut: f32.Point{X: +14.142136, Y: -14.142136}},
{l: -20, ptIn: f32.Point{X: -30, Y: +30}, ptOut: f32.Point{X: +14.142136, Y: -14.142136}},
{l: -20, ptIn: f32.Point{X: -90, Y: +90}, ptOut: f32.Point{X: +14.142137, Y: -14.142137}},
// l!=0 && Hypot=l
{l: 5, ptIn: f32.Point{X: 3, Y: 4}, ptOut: f32.Point{X: 3, Y: 4}},
{l: 5, ptIn: f32.Point{X: 3, Y: -4}, ptOut: f32.Point{X: 3, Y: -4}},
{l: 5, ptIn: f32.Point{X: -3, Y: -4}, ptOut: f32.Point{X: -3, Y: -4}},
{l: 5, ptIn: f32.Point{X: -3, Y: 4}, ptOut: f32.Point{X: -3, Y: 4}},
{l: -5, ptIn: f32.Point{X: 3, Y: 4}, ptOut: f32.Point{X: -3, Y: -4}},
{l: -5, ptIn: f32.Point{X: 3, Y: -4}, ptOut: f32.Point{X: -3, Y: 4}},
{l: -5, ptIn: f32.Point{X: -3, Y: -4}, ptOut: f32.Point{X: 3, Y: 4}},
{l: -5, ptIn: f32.Point{X: -3, Y: 4}, ptOut: f32.Point{X: 3, Y: -4}},
}
for i, s := range scenarios {