Help! the compareFunction is not working?

请问backstopjs支持在backstop.json中调用自定义的对比方法么，我写了一个customCompare.js文件实现视觉对比时允许元素在任意方向下有指定像素的偏差，我把这个文件放到了backstop.json中的engineOptions下，如
"engineOptions": {
"compareFunction": "customCompare.js"
}
但是执行backstop测试后查看报告却没有生效，是什么原因呢？是哪里配置有问题么？
我查看了很多资料也没有找到解决方法，盼回复！

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Does backstopjs support calling custom comparison methods in backstop.json? I wrote a customCompare.js file to allow for a specified pixel deviation in any direction during visual comparison. I placed this file under engineOptions in backstop.json, like this:
"engineOptions": {

"compareFunction": "customCompare.js"

}
However, after executing backstop, the report does not reflect the changes. What could be the reason? Is there a configuration issue somewhere? I've looked through a lot of resources but haven't found a solution. Looking forward to your reply!