CPU patterns fallback

internal/generator/cpu_moving_square.go

@@ -0,0 +1,73 @@
+package generator
+
+import "math"
+
+const movingSquareSize = 150
+
+type baseColorFunc func(x, y, width, height int) YCbCr10
+
+type squareBounds struct {
+	minX float64
+	maxX float64
+	minY float64
+	maxY float64
+}
+
+func movingSquareBounds(width, height, frameIndex int) squareBounds {
+	const half = float64(movingSquareSize) / 2
+	centerX := float64(width) / 2
+	centerY := float64(height) / 2
+	time := float64(frameIndex) / 25.0
+	offset := math.Sin(time*0.5) * (centerX - half)
+	return squareBounds{
+		minX: centerX - half + offset,
+		maxX: centerX + half + offset,
+		minY: centerY - half,
+		maxY: centerY + half,
+	}
+}
+
+func (b squareBounds) contains(x, y int) bool {
+	return float64(x) >= b.minX && float64(x) < b.maxX &&
+		float64(y) >= b.minY && float64(y) < b.maxY
+}
+
+func patchMovingSquare(
+	dst []byte,
+	width, height, frameIndex int,
+	baseColor baseColorFunc,
+) error {
+	bounds := movingSquareBounds(width, height, frameIndex)
+
+	firstPixelX := max(0, int(math.Floor(bounds.minX)))
+	lastPixelX := min(width, int(math.Ceil(bounds.maxX)))
+	firstBlockX := firstPixelX / 6 * 6
+	lastBlockX := min(width, (lastPixelX+5)/6*6)
+	firstY := max(0, int(math.Floor(bounds.minY)))
+	lastY := min(height, int(math.Ceil(bounds.maxY)))
+
+	for y := firstY; y < lastY; y++ {
+		for x := firstBlockX; x < lastBlockX; x += 6 {
+			var pixels [6]YCbCr10
+			for i := range pixels {
+				px := x + i
+				color := baseColor(px, y, width, height)
+				if bounds.contains(px, y) {
+					color = invertStudioRange(color)
+				}
+				pixels[i] = color
+			}
+			offset := (y*width + x) / 6 * 16
+			packV210Block(dst[offset:offset+16], pixels)
+		}
+	}
+	return nil
+}
+
+func invertStudioRange(color YCbCr10) YCbCr10 {
+	return YCbCr10{
+		Y:  1004 - color.Y,
+		Cb: 1024 - color.Cb,
+		Cr: 1024 - color.Cr,
+	}
+}