draw: add a test for src translation invariance.

Change-Id: Iedd4cc4e2b88c5fa9e4fcd547756588e4d87bfff
Reviewed-on: https://go-review.googlesource.com/7471
Reviewed-by: Rob Pike <r@golang.org>
This commit is contained in:
Nigel Tao 2015-03-12 17:50:07 +11:00
parent efa0c0977f
commit 4bf24024c9
2 changed files with 58 additions and 0 deletions

View File

@ -131,6 +131,64 @@ func TestScaleClipCommute(t *testing.T) {
} }
} }
// translatedImage is an image m translated by t.
type translatedImage struct {
m image.Image
t image.Point
}
func (t *translatedImage) At(x, y int) color.Color { return t.m.At(x-t.t.X, y-t.t.Y) }
func (t *translatedImage) Bounds() image.Rectangle { return t.m.Bounds().Add(t.t) }
func (t *translatedImage) ColorModel() color.Model { return t.m.ColorModel() }
// TestSrcTranslationInvariance tests that Scale and Transform are invariant
// under src translations. Specifically, when some source pixels are not in the
// bottom-right quadrant of src coordinate space, we consistently round down,
// not round towards zero.
func TestSrcTranslationInvariance(t *testing.T) {
f, err := os.Open("../testdata/testpattern.png")
if err != nil {
t.Fatalf("Open: %v", err)
}
defer f.Close()
src, _, err := image.Decode(f)
if err != nil {
t.Fatalf("Decode: %v", err)
}
qs := []Interpolator{
NearestNeighbor,
ApproxBiLinear,
CatmullRom,
}
deltas := []image.Point{
{+0, +0},
{+0, +5},
{+0, -5},
{+5, +0},
{-5, +0},
{+8, +8},
{+8, -8},
{-8, +8},
{-8, -8},
}
for _, q := range qs {
want := image.NewRGBA(image.Rect(0, 0, 200, 200))
q.Scale(want, want.Bounds(), src, src.Bounds(), nil)
for _, delta := range deltas {
tsrc := &translatedImage{src, delta}
got := image.NewRGBA(image.Rect(0, 0, 200, 200))
q.Scale(got, got.Bounds(), tsrc, tsrc.Bounds(), nil)
if !bytes.Equal(got.Pix, want.Pix) {
t.Errorf("pix differ for delta=%v, q=%T", delta, q)
}
// TODO: Transform.
}
}
}
// The fooWrapper types wrap the dst or src image to avoid triggering the // The fooWrapper types wrap the dst or src image to avoid triggering the
// type-specific fast path implementations. // type-specific fast path implementations.
type ( type (

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