ligmen: include frame times in image ids

ligmen/formats.go

@@ -0,0 +1,24 @@
+package ligmen
+
+import (
+	"image"
+	"time"
+)
+
+// Image is a potentially animated image.
+type Image[Frame image.Image] struct {
+	// Frames is animation's frame images.
+	// An image that is not animated has a single frame.
+	Frames []Frame
+	// Times is the duration of each frame.
+	// An image that is not animated has a single frame duration of 0.
+	Times []time.Duration
+}
+
+// Static is a helper to create an Image with a single frame.
+func Static[Frame image.Image](img Frame) Image[Frame] {
+	return Image[Frame]{
+		Frames: []Frame{img},
+		Times:  []time.Duration{0},
+	}
+}

ligmen/hash.go

@@ -14,14 +14,14 @@ import (
 type ID [28]byte
 
 // Hash computes the content ID for an image or animation.
-func Hash[Image image.Image](frames []Image) ID {
+func Hash[Frame image.Image](anim Image[Frame]) ID {
 	// NOTE(zephyr): We assume animations always loop forever.
 	// The behavior in browsers when they don't is that every instance shares a
 	// single loop count, so they quickly stop repeating as posted.
 	h := sha3.New224()
 	d := make([]byte, 8, 28)
 	var bounds image.Rectangle
-	for _, f := range frames {
+	for _, f := range anim.Frames {
 		if bounds == (image.Rectangle{}) {
 			bounds = f.Bounds().Canon()
 		}
@@ -37,10 +37,12 @@ func Hash[Image image.Image](frames []Image) ID {
 			h.Write(d)
 		}
 	}
-	d = d[:12]
+	for _, t := range anim.Times {
+		binary.BigEndian.PutUint64(d, uint64(t.Nanoseconds()))
+		h.Write(d)
+	}
 	binary.BigEndian.PutUint32(d, uint32(bounds.Dx()))
 	binary.BigEndian.PutUint32(d[4:], uint32(bounds.Dy()))
-	binary.BigEndian.PutUint32(d[8:], uint32(len(frames)))
 	h.Write(d)
 	return ID(h.Sum(d[:0]))
 }

ligmen/hash_test.go

@@ -4,6 +4,7 @@ import (
 	"image"
 	"image/color"
 	"testing"
+	"time"
 
 	"ligmotes.com/ligmen"
 )
@@ -36,70 +37,133 @@ func (img *testimg) At(x int, y int) color.Color {
 func TestHash(t *testing.T) {
 	// We test that hashing a number of similar images doesn't produce collisions.
 	cases := []struct {
-		name   string
+		name string
-		frames []image.RGBA64Image
+		anim ligmen.Image[image.RGBA64Image]
 	}{
 		{
 			name: "clear-square",
-			frames: []image.RGBA64Image{
+			anim: ligmen.Static[image.RGBA64Image](&testimg{px: []color.RGBA64{{}, {}, {}, {}}, w: 2, h: 2}),
-				&testimg{px: []color.RGBA64{{}, {}, {}, {}}, w: 2, h: 2},
-			},
 		},
 		{
 			name: "topleft-square",
-			frames: []image.RGBA64Image{
+			anim: ligmen.Static[image.RGBA64Image](&testimg{px: []color.RGBA64{{A: 1}, {}, {}, {}}, w: 2, h: 2}),
-				&testimg{px: []color.RGBA64{{A: 1}, {}, {}, {}}, w: 2, h: 2},
-			},
 		},
 		{
 			name: "topright-square",
-			frames: []image.RGBA64Image{
+			anim: ligmen.Static[image.RGBA64Image](&testimg{px: []color.RGBA64{{}, {A: 1}, {}, {}}, w: 2, h: 2}),
-				&testimg{px: []color.RGBA64{{}, {A: 1}, {}, {}}, w: 2, h: 2},
-			},
 		},
 		{
 			name: "botleft-square",
-			frames: []image.RGBA64Image{
+			anim: ligmen.Static[image.RGBA64Image](&testimg{px: []color.RGBA64{{}, {}, {A: 1}, {}}, w: 2, h: 2}),
-				&testimg{px: []color.RGBA64{{}, {}, {A: 1}, {}}, w: 2, h: 2},
-			},
 		},
 		{
 			name: "botright-square",
-			frames: []image.RGBA64Image{
+			anim: ligmen.Static[image.RGBA64Image](&testimg{px: []color.RGBA64{{}, {}, {}, {A: 1}}, w: 2, h: 2}),
-				&testimg{px: []color.RGBA64{{}, {}, {}, {A: 1}}, w: 2, h: 2},
-			},
 		},
 		{
 			name: "all-square",
-			frames: []image.RGBA64Image{
+			anim: ligmen.Static[image.RGBA64Image](&testimg{px: []color.RGBA64{{A: 1}, {A: 1}, {A: 1}, {A: 1}}, w: 2, h: 2}),
-				&testimg{px: []color.RGBA64{{A: 1}, {A: 1}, {A: 1}, {A: 1}}, w: 2, h: 2},
+		},
-			},
+		{
+			name: "red-square",
+			anim: ligmen.Static[image.RGBA64Image](&testimg{px: []color.RGBA64{{R: 1, A: 1}, {}, {}, {}}, w: 2, h: 2}),
+		},
+		{
+			name: "green-square",
+			anim: ligmen.Static[image.RGBA64Image](&testimg{px: []color.RGBA64{{G: 1, A: 1}, {}, {}, {}}, w: 2, h: 2}),
+		},
+		{
+			name: "blue-square",
+			anim: ligmen.Static[image.RGBA64Image](&testimg{px: []color.RGBA64{{B: 1, A: 1}, {}, {}, {}}, w: 2, h: 2}),
+		},
+		{
+			name: "gray-square",
+			anim: ligmen.Static[image.RGBA64Image](&testimg{px: []color.RGBA64{{R: 1, G: 1, B: 1, A: 1}, {}, {}, {}}, w: 2, h: 2}),
 		},
 		{
 			name: "row",
-			frames: []image.RGBA64Image{
+			anim: ligmen.Static[image.RGBA64Image](&testimg{px: []color.RGBA64{{}, {}, {}, {}}, w: 4, h: 1}),
-				&testimg{px: []color.RGBA64{{}, {}, {}, {}}, w: 4, h: 1},
-			},
 		},
 		{
 			name: "col",
-			frames: []image.RGBA64Image{
+			anim: ligmen.Static[image.RGBA64Image](&testimg{px: []color.RGBA64{{}, {}, {}, {}}, w: 1, h: 4}),
-				&testimg{px: []color.RGBA64{{}, {}, {}, {}}, w: 1, h: 4},
-			},
 		},
 		{
 			name: "frames",
-			frames: []image.RGBA64Image{
+			anim: ligmen.Image[image.RGBA64Image]{
-				&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+				Frames: []image.RGBA64Image{
-				&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
-				&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
-				&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+				},
+				Times: []time.Duration{1, 1, 1, 1},
+			},
+		},
+		{
+			name: "frames-first",
+			anim: ligmen.Image[image.RGBA64Image]{
+				Frames: []image.RGBA64Image{
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+				},
+				Times: []time.Duration{2, 1, 1, 1},
+			},
+		},
+		{
+			name: "frames-second",
+			anim: ligmen.Image[image.RGBA64Image]{
+				Frames: []image.RGBA64Image{
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+				},
+				Times: []time.Duration{1, 2, 1, 1},
+			},
+		},
+		{
+			name: "frames-third",
+			anim: ligmen.Image[image.RGBA64Image]{
+				Frames: []image.RGBA64Image{
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+				},
+				Times: []time.Duration{1, 1, 2, 1},
+			},
+		},
+		{
+			name: "frames-fourth",
+			anim: ligmen.Image[image.RGBA64Image]{
+				Frames: []image.RGBA64Image{
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+				},
+				Times: []time.Duration{1, 1, 1, 2},
+			},
+		},
+		{
+			name: "frames-all",
+			anim: ligmen.Image[image.RGBA64Image]{
+				Frames: []image.RGBA64Image{
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+					&testimg{px: []color.RGBA64{{}}, w: 1, h: 1},
+				},
+				Times: []time.Duration{2, 2, 2, 2},
 			},
 		},
 	}
 	m := make(map[ligmen.ID]string)
 	for _, c := range cases {
-		id := ligmen.Hash(c.frames)
+		id := ligmen.Hash(c.anim)
 		if had, ok := m[id]; ok {
 			t.Errorf("%s collides with %s @ %v", c.name, had, id)
 			continue
@@ -109,7 +173,8 @@ func TestHash(t *testing.T) {
 }
 
 func TestIDRoundTrip(t *testing.T) {
-	id := ligmen.Hash([]*testimg{{px: []color.RGBA64{{}, {}, {}, {}}, w: 2, h: 2}})
+	img := ligmen.Static(&testimg{px: []color.RGBA64{{}, {}, {}, {}}, w: 2, h: 2})
+	id := ligmen.Hash(img)
 	if id == (ligmen.ID{}) {
 		t.Error("empty id for image")
 	}