From d3b4836e79a8c5aed14055f7db651603dedff873 Mon Sep 17 00:00:00 2001
From: CPPAlien <creaspan@gmail.com>
Date: Tue, 10 Jul 2018 19:47:41 +0800
Subject: [PATCH] =?UTF-8?q?=E4=BF=AE=E5=A4=8D=20Android=20=E6=9C=BA?=
 =?UTF-8?q?=E5=9E=8B=E4=B8=8A=E5=9C=86=E8=A7=92=E5=9B=BE=E7=89=87=E6=97=A0?=
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---
 lib/pen.js | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/pen.js b/lib/pen.js
index 7b79ed1..31dae80 100644
--- a/lib/pen.js
+++ b/lib/pen.js
@@ -75,7 +75,10 @@ export default class Painter {
   _doBorder(borderRadius, width, height) {
     if (borderRadius && width && height) {
       const r = Math.min(borderRadius.toPx(), width / 2, height / 2);
-      this.ctx.setFillStyle("rgba(0, 0, 0, 0)");
+      // 防止在某些机型上周边有黑框现象，此处如果直接设置 setFillStyle 为透明，在 Android 机型上会导致被裁减的图片也变为透明， iOS 和 IDE 上不会
+      // setGlobalAlpha 在 1.9.90 起支持，低版本下无效，但把 setFillStyle 设为了 white，相对默认的 black 要好点
+      this.ctx.setGlobalAlpha(0);
+      this.ctx.setFillStyle("white");
       this.ctx.beginPath();
       this.ctx.arc(-width / 2 + r, -height / 2 + r, r, 1 * Math.PI, 1.5 * Math.PI);
       this.ctx.lineTo(width / 2 - r, -height / 2);
@@ -92,6 +95,7 @@ export default class Painter {
           getApp().systemInfo.platform === 'ios')) {
         this.ctx.clip();
       }
+      this.ctx.setGlobalAlpha(1);
     }
   }