shareable: Add gaps between images

After this change, each image on the texture atlases has a
transparent border around it.

This change removes the hack to round texels not to violate the
source regions.

Fixes #1194
Updates #1171

image_test.go

@@ -2065,3 +2065,27 @@ func BenchmarkImageDrawOver(b *testing.B) {
 		draw.Draw(dst, dst.Bounds(), src, image.ZP, draw.Over)
 	}
 }
+
+// Issue #1171
+func TestImageFloatTranslate(t *testing.T) {
+	const w, h = 32, 32
+
+	dst, _ := NewImage(320, 240, FilterDefault)
+	src, _ := NewImage(w, h, FilterDefault)
+	src.Fill(color.RGBA{0xff, 0, 0, 0xff})
+
+	op := &DrawImageOptions{}
+	op.GeoM.Scale(2, 2)
+	op.GeoM.Translate(0, 0.501)
+	dst.DrawImage(src, op)
+
+	for j := 1; j < h*2+1; j++ {
+		for i := 0; i < w*2; i++ {
+			got := dst.At(i, j)
+			want := color.RGBA{0xff, 0, 0, 0xff}
+			if got != want {
+				t.Errorf("At(%d, %d): got: %v, want: %v", i, j, got, want)
+			}
+		}
+	}
+}

internal/graphicscommand/command.go

@@ -209,7 +209,6 @@ func fract(x float32) float32 {
 
 const (
 	dstAdjustmentFactor = 1.0 / 256.0
-	texelAdjustmentFactor = 1.0 / 512.0
 )
 
 // Flush flushes the command queue.
@@ -254,10 +253,6 @@ func (q *commandQueue) Flush() error {
 			case 0.5 <= f && f < 0.5+dstAdjustmentFactor:
 				vs[i*graphics.VertexFloatNum+1] += (0.5 + dstAdjustmentFactor) - f
 			}
-
-			// Adjust regions not to violate neighborhoods (#317, #558, #724).
-			vs[i*graphics.VertexFloatNum+6] -= 1.0 / s.width * texelAdjustmentFactor
-			vs[i*graphics.VertexFloatNum+7] -= 1.0 / s.height * texelAdjustmentFactor
 		}
 	} else {
 		n := q.nvertices / graphics.VertexFloatNum
@@ -442,12 +437,6 @@ func (c *drawTrianglesCommand) Exec(indexOffset int) error {
 					region[3] / float32(h),
 				}
 
-				// Adjust regions not to violate neighborhoods (#317, #558, #724).
-				if theGraphicsDriver.HasHighPrecisionFloat() {
-					vs[2] -= 1.0 / float32(w) * texelAdjustmentFactor
-					vs[3] -= 1.0 / float32(h) * texelAdjustmentFactor
-				}
-
 				us[i] = vs
 			default:
 				us[i] = v

internal/shareable/image.go

@@ -28,6 +28,12 @@ import (
 	"github.com/hajimehoshi/ebiten/internal/restorable"
 )
 
+const (
+	// borderSize represents the size of border around an image.
+	// Every image or node except for a screen image has its border.
+	borderSize = 1
+)
+
 var graphicsDriver driver.Graphics
 
 func SetGraphicsDriver(graphics driver.Graphics) {
@@ -197,7 +203,7 @@ func (i *Image) ensureNotShared() {
 		return
 	}
 
-	ox, oy, w, h := i.region()
+	ox, oy, w, h := i.regionWithBorder()
 	dx0 := float32(0)
 	dy0 := float32(0)
 	dx1 := float32(w)
@@ -240,7 +246,7 @@ func (i *Image) makeShared() error {
 	pixels := make([]byte, 4*i.width*i.height)
 	for y := 0; y < i.height; y++ {
 		for x := 0; x < i.width; x++ {
-			r, g, b, a, err := i.at(x, y)
+			r, g, b, a, err := i.at(x+borderSize, y+borderSize)
 			if err != nil {
 				return err
 			}
@@ -256,12 +262,12 @@ func (i *Image) makeShared() error {
 	return nil
 }
 
-func (i *Image) region() (x, y, width, height int) {
+func (i *Image) regionWithBorder() (x, y, width, height int) {
 	if i.backend == nil {
 		panic("shareable: backend must not be nil: not allocated yet?")
 	}
 	if !i.isShared() {
-		return 0, 0, i.width, i.height
+		return 0, 0, i.width + 2*borderSize, i.height + 2*borderSize
 	}
 	return i.node.Region()
 }
@@ -321,12 +327,22 @@ func (i *Image) DrawTriangles(img *Image, vertices []float32, indices []uint16,
 		}
 	}
 
+	var dx, dy float32
+	// A screen image doesn't have its border.
+	if !i.screen {
+		dx = borderSize
+		dy = borderSize
+	}
 	var oxf, oyf float32
 	if len(srcs) > 0 {
-		ox, oy, _, _ := srcs[0].region()
+		ox, oy, _, _ := srcs[0].regionWithBorder()
+		ox += borderSize
+		oy += borderSize
 		oxf, oyf = float32(ox), float32(oy)
 		n := len(vertices) / graphics.VertexFloatNum
 		for i := 0; i < n; i++ {
+			vertices[i*graphics.VertexFloatNum+0] += dx
+			vertices[i*graphics.VertexFloatNum+1] += dy
 			vertices[i*graphics.VertexFloatNum+2] += oxf
 			vertices[i*graphics.VertexFloatNum+3] += oyf
 			vertices[i*graphics.VertexFloatNum+4] += oxf
@@ -420,19 +436,33 @@ func (i *Image) replacePixels(pix []byte) {
 		i.allocate(true)
 	}
 
-	x, y, w, h := i.region()
-	if pix != nil {
-		if l := 4 * w * h; len(pix) != l {
+	x, y, w, h := i.regionWithBorder()
+	if pix == nil {
+		i.backend.restorable.ReplacePixels(nil, x, y, w, h)
+		return
+	}
+
+	ow, oh := w-2*borderSize, h-2*borderSize
+	if l := 4 * ow * oh; len(pix) != l {
 		panic(fmt.Sprintf("shareable: len(p) must be %d but %d", l, len(pix)))
 	}
+
+	// Add a border around the image.
+	pixb := make([]byte, 4*w*h)
+	for j := 0; j < oh; j++ {
+		copy(pixb[4*((j+borderSize)*w+borderSize):], pix[4*j*ow:4*(j+1)*ow])
 	}
-	i.backend.restorable.ReplacePixels(pix, x, y, w, h)
+
+	i.backend.restorable.ReplacePixels(pixb, x, y, w, h)
 }
 
 func (img *Image) Pixels(x, y, width, height int) ([]byte, error) {
 	backendsM.Lock()
 	defer backendsM.Unlock()
 
+	x += borderSize
+	y += borderSize
+
 	bs := make([]byte, 4*width*height)
 	idx := 0
 	for j := y; j < y+height; j++ {
@@ -456,7 +486,7 @@ func (i *Image) at(x, y int) (byte, byte, byte, byte, error) {
 		return 0, 0, 0, 0, nil
 	}
 
-	ox, oy, w, h := i.region()
+	ox, oy, w, h := i.regionWithBorder()
 	if x < 0 || y < 0 || x >= w || y >= h {
 		return 0, 0, 0, 0, nil
 	}
@@ -506,7 +536,7 @@ func (i *Image) dispose(markDisposed bool) {
 	i.backend.page.Free(i.node)
 	if !i.backend.page.IsEmpty() {
 		// As this part can be reused, this should be cleared explicitly.
-		i.backend.restorable.ClearPixels(i.region())
+		i.backend.restorable.ClearPixels(i.regionWithBorder())
 		return
 	}
 
@@ -554,6 +584,7 @@ func (i *Image) allocate(shareable bool) {
 	runtime.SetFinalizer(i, (*Image).MarkDisposed)
 
 	if i.screen {
+		// A screen image doesn't have a border.
 		i.backend = &backend{
 			restorable: restorable.NewScreenFramebufferImage(i.width, i.height),
 		}
@@ -562,13 +593,13 @@ func (i *Image) allocate(shareable bool) {
 
 	if !shareable || !i.shareable() {
 		i.backend = &backend{
-			restorable: restorable.NewImage(i.width, i.height, i.volatile),
+			restorable: restorable.NewImage(i.width+2*borderSize, i.height+2*borderSize, i.volatile),
 		}
 		return
 	}
 
 	for _, b := range theBackends {
-		if n, ok := b.TryAlloc(i.width, i.height); ok {
+		if n, ok := b.TryAlloc(i.width+2*borderSize, i.height+2*borderSize); ok {
 			i.backend = b
 			i.node = n
 			return
@@ -588,7 +619,7 @@ func (i *Image) allocate(shareable bool) {
 	}
 	theBackends = append(theBackends, b)
 
-	n := b.page.Alloc(i.width, i.height)
+	n := b.page.Alloc(i.width+2*borderSize, i.height+2*borderSize)
 	if n == nil {
 		panic("shareable: Alloc result must not be nil at allocate")
 	}

internal/shareable/image_test.go

@@ -191,7 +191,7 @@ func TestReshared(t *testing.T) {
 			a := pix[4*(size*j+i)+3]
 			got := color.RGBA{r, g, b, a}
 			if got != want {
-				t.Errorf("got: %v, want: %v", got, want)
+				t.Errorf("At(%d, %d): got: %v, want: %v", i, j, got, want)
 			}
 		}
 	}
@@ -214,7 +214,7 @@ func TestReshared(t *testing.T) {
 			a := pix[4*(size*j+i)+3]
 			got := color.RGBA{r, g, b, a}
 			if got != want {
-				t.Errorf("got: %v, want: %v", got, want)
+				t.Errorf("At(%d, %d): got: %v, want: %v", i, j, got, want)
 			}
 		}
 	}