解决Android启动图拉伸问题

https://ask.dcloud.net.cn/article/35527

https://github.com/pingerx/AndroidSample/blob/master/sample/src/main/java/com/pinger/sample/pointnine/点九图简单制作教程.md

https://ext.dcloud.net.cn/plugin?id=1936

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打包时报错 ...error: top-left corner pixel must be either opaque white or transparent. ..
这句话的字面意思是 "左上角像素必须是全透明或者不透明的白底"