文字颜色默认黑色

src/toCanvas.ts

@@ -191,7 +191,7 @@ function drawText(data: INodeData, ctx: CanvasRenderingContext2D, scale: number)
 
 	ctx.font = font;
 	ctx.textBaseline = "bottom";
-	ctx.fillStyle = color;
+	ctx.fillStyle = color||"black";
 	var textMetrics = ctx.measureText(text);
 	let widthAll = textMetrics.width;