fix: 测试截图

public/lib/potree/potree.js

@@ -24160,7 +24160,7 @@
     		_stencil = parameters.stencil !== undefined ? parameters.stencil : true,
     		_antialias = parameters.antialias !== undefined ? parameters.antialias : false,
     		_premultipliedAlpha = parameters.premultipliedAlpha !== undefined ? parameters.premultipliedAlpha : true,
-    		_preserveDrawingBuffer = parameters.preserveDrawingBuffer !== undefined ? parameters.preserveDrawingBuffer : false,
+    		_preserveDrawingBuffer = true,
     		_powerPreference = parameters.powerPreference !== undefined ? parameters.powerPreference : 'default',
     		_failIfMajorPerformanceCaveat = parameters.failIfMajorPerformanceCaveat !== undefined ? parameters.failIfMajorPerformanceCaveat : false;
 
@@ -95981,7 +95981,7 @@ void main() {
     	}
 
     	initTHREE () {
-    		this.renderer = new WebGLRenderer({alpha: true, premultipliedAlpha: false});
+    		this.renderer = new WebGLRenderer({alpha: true, premultipliedAlpha: false, preserveDrawingBuffer: true });
     		this.renderer.setClearColor(0x000000, 0);
     		this.renderer.setSize(10, 10);
     		this.renderer.autoClear = false;