Text + MXL logo pattern

internal/generator/logo_test.go

@@ -0,0 +1,64 @@
+package generator
+
+import (
+	"image"
+	"image/color"
+	"testing"
+)
+
+func TestBuildLogoPlane(t *testing.T) {
+	// 8x4 logo: white left half, near-75% red right half (8-bit 191 is
+	// 0.749, a hair under the exact-0.75 bars value, hence Y=203 not 204),
+	// one transparent pixel at (2,1).
+	img := image.NewRGBA(image.Rect(0, 0, 8, 4))
+	for yy := 0; yy < 4; yy++ {
+		for xx := 0; xx < 8; xx++ {
+			if xx < 4 {
+				img.Set(xx, yy, color.RGBA{255, 255, 255, 255})
+			} else {
+				img.Set(xx, yy, color.RGBA{191, 0, 0, 255})
+			}
+		}
+	}
+	img.Set(2, 1, color.RGBA{0, 0, 0, 0})
+
+	plane, err := BuildLogoPlane(img)
+	if err != nil {
+		t.Fatalf("BuildLogoPlane: %v", err)
+	}
+	if len(plane) != 1+8*4 {
+		t.Fatalf("plane len=%d, want 33", len(plane))
+	}
+	if hdr := plane[0]; hdr != 8|4<<16 {
+		t.Fatalf("header=%#x, want w=8 h=4", hdr)
+	}
+	cases := []struct {
+		dx, dy    int
+		opaque    bool
+		y, cb, cr uint32
+	}{
+		{1, 1, true, 940, 512, 512}, // white
+		{5, 2, true, 203, 435, 848}, // near-75% red
+		{2, 1, false, 0, 0, 0},      // transparent
+	}
+	for _, c := range cases {
+		s := plane[1+c.dy*8+c.dx]
+		if got := (s >> 30) & 1; got != boolToBit(c.opaque) {
+			t.Fatalf("pixel (%d,%d): opaque=%d, want %v", c.dx, c.dy, got, c.opaque)
+		}
+		if !c.opaque {
+			continue
+		}
+		if s&0x3FF != c.y || (s>>10)&0x3FF != c.cb || (s>>20)&0x3FF != c.cr {
+			t.Fatalf("pixel (%d,%d): got %d/%d/%d, want %d/%d/%d",
+				c.dx, c.dy, s&0x3FF, (s>>10)&0x3FF, (s>>20)&0x3FF, c.y, c.cb, c.cr)
+		}
+	}
+}
+
+func boolToBit(b bool) uint32 {
+	if b {
+		return 1
+	}
+	return 0
+}