ebiten: Add AddressUnsafe

Fixes #1219

examples/polygons/main.go

@@ -121,6 +121,7 @@ func (g *Game) Update(screen *ebiten.Image) error {
 
 func (g *Game) Draw(screen *ebiten.Image) {
 	op := &ebiten.DrawTrianglesOptions{}
+	op.Address = ebiten.AddressUnsafe
 	indices := []uint16{}
 	for i := 0; i < g.ngon; i++ {
 		indices = append(indices, uint16(i), uint16(i+1)%uint16(g.ngon), uint16(g.ngon))

image.go

@@ -234,6 +234,9 @@ const (
 
 	// AddressRepeat means that texture coordinates wrap to the other side of the texture.
 	AddressRepeat Address = Address(driver.AddressRepeat)
+
+	// AddressUnsafe means there is no guarantee when the texture coodinates are out of range.
+	AddressUnsafe Address = Address(driver.AddressUnsafe)
 )
 
 // DrawTrianglesOptions represents options to render triangles on an image.
@@ -323,13 +326,16 @@ func (i *Image) DrawTriangles(vertices []Vertex, indices []uint16, img *Image, o
 	is := make([]uint16, len(indices))
 	copy(is, indices)
 
+	var sr driver.Region
+	if options.Address != AddressUnsafe {
 		b := img.Bounds()
-	sr := driver.Region{
+		sr = driver.Region{
 			X:      float32(b.Min.X),
 			Y:      float32(b.Min.Y),
 			Width:  float32(b.Dx()),
 			Height: float32(b.Dy()),
 		}
+	}
 
 	i.buffered.DrawTriangles(img.buffered, vs, is, options.ColorM.impl, mode, filter, driver.Address(options.Address), sr, nil, nil)
 }