wip: 获取dpr

GauharChan · Jan 11, 2024 · ed5360e · ed5360e
1 parent 3f5a9e9
commit ed5360e
Showing 1 changed file with 36 additions and 0 deletions.
diff --git a/docs/工作常用代码.md b/docs/工作常用代码.md
@@ -965,3 +965,39 @@ export function downLoadByBlob(res) {
   window.URL.revokeObjectURL(href); // 释放掉blob对象
 }
 ```
+
+### 微信H5打开小程序
+
+https://developers.weixin.qq.com/doc/offiaccount/OA_Web_Apps/Wechat_Open_Tag.html#21
+
+### web获取dpr
+
+传递`canvas`的`context`
+
+```ts
+function getRatio (context: any): number {
+  if (!context) {
+    return 1
+  }
+  const backingStore =
+    context.backingStorePixelRatio ||
+    context.webkitBackingStorePixelRatio ||
+    context.mozBackingStorePixelRatio ||
+    context.msBackingStorePixelRatio ||
+    context.oBackingStorePixelRatio ||
+    context.backingStorePixelRatio ||
+    1
+  return (window.devicePixelRatio || 1) / backingStore
+}
+```
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