Reland(2): graphics: Appropriate rendering of edges on linear filter

image_test.go

@@ -25,6 +25,7 @@ import (
 	"testing"
 
 	. "github.com/hajimehoshi/ebiten"
+	"github.com/hajimehoshi/ebiten/ebitenutil"
 	emath "github.com/hajimehoshi/ebiten/internal/math"
 )
 
@@ -595,3 +596,28 @@ func BenchmarkDrawImage(b *testing.B) {
 		img0.DrawImage(img1, op)
 	}
 }
+
+func TestImageLinear(t *testing.T) {
+	src, _ := NewImage(32, 32, FilterLinear)
+	dst, _ := NewImage(64, 64, FilterNearest)
+	src.Fill(color.RGBA{0, 0xff, 0, 0xff})
+	ebitenutil.DrawRect(src, 8, 8, 16, 16, color.RGBA{0xff, 0, 0, 0xff})
+
+	op := &DrawImageOptions{}
+	op.GeoM.Translate(8, 8)
+	op.GeoM.Scale(2, 2)
+	r := image.Rect(8, 8, 24, 24)
+	op.SourceRect = &r
+	dst.DrawImage(src, op)
+
+	for j := 0; j < 64; j++ {
+		for i := 0; i < 64; i++ {
+			c := color.RGBAModel.Convert(dst.At(i, j)).(color.RGBA)
+			got := c.G
+			want := uint8(0)
+			if got != want {
+				t.Errorf("dst At(%d, %d).G: got %#v, want: %#v", i, j, got, want)
+			}
+		}
+	}
+}