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mipmap: Bug fix: Scale could be Inf/0 and caused a forever loop

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Fixes #1398
This commit is contained in:
Hajime Hoshi 2020-10-21 10:38:10 +09:00
parent aaa675bc2a
commit a3cb78558b
2 changed files with 41 additions and 5 deletions
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21
image_test.go
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@ -2128,3 +2128,24 @@ func TestImageZeroTriangle(t *testing.T) {
is := []uint16{}
dst.DrawTriangles(vs, is, src, nil)
}
// Issue #1398
func TestImageDrawImageTooBigScale(t *testing.T) {
dst := NewImage(1, 1)
src := NewImage(1, 1)
op := &DrawImageOptions{}
op.GeoM.Scale(1e20, 1e20)
dst.DrawImage(src, op)
}
// Issue #1398
func TestImageDrawImageTooSmallScale(t *testing.T) {
dst := NewImage(1, 1)
src := NewImage(1, 1)
op := &DrawImageOptions{}
op.Filter = FilterLinear
op.GeoM.Scale(1e-10, 1e-10)
dst.DrawImage(src, op)
}

25
internal/mipmap/mipmap.go
View File

@ -271,6 +271,8 @@ func (m *Mipmap) disposeMipmaps() {
// mipmapLevel returns an appropriate mipmap level for the given distance.
func mipmapLevelFromDistance(dx0, dy0, dx1, dy1, sx0, sy0, sx1, sy1 float32, filter driver.Filter) int {
const maxScale = 6
if filter == driver.FilterScreen {
return 0
}
@ -282,6 +284,19 @@ func mipmapLevelFromDistance(dx0, dy0, dx1, dy1, sx0, sy0, sx1, sy1 float32, fil
}
scale := d / s
// Scale can be infinite when the specified scale is extremely big (#1398).
if math.IsInf(float64(scale), 0) {
if filter == driver.FilterNearest {
return -maxScale
}
return 0
}
// Scale can be zero when the specified scale is extremely small (#1398).
if scale == 0 {
return 0
}
// Use 'negative' mipmap to render edges correctly (#611, #907).
// It looks like 128 is the enlargement factor that causes edge missings to pass the test TestImageStretch,
// but we use 32 here for environments where the float precision is low (#1044, #1270).
@ -310,10 +325,10 @@ func mipmapLevelFromDistance(dx0, dy0, dx1, dy1, sx0, sy0, sx1, sy1 float32, fil
}
}
// If tooBigScale is 64, level -6 means that the maximum scale is 64 * 2^6 = 4096. This should be
// If tooBigScale is 32, level -6 means that the maximum scale is 32 * 2^6 = 2048. This should be
// enough.
if level < -6 {
level = -6
if level < -maxScale {
level = -maxScale
}
return level
}
@ -346,8 +361,8 @@ func mipmapLevelFromDistance(dx0, dy0, dx1, dy1, sx0, sy0, sx1, sy1 float32, fil
}
}
if level > 6 {
level = 6
if level > maxScale {
level = maxScale
}
return level