feat: watermark (#203)

* feat: add watermark

src/utils/operate/index.ts

@@ -1,3 +1,5 @@
+import type { FunctionArgs } from "@vueuse/core";
+
 export const hasClass = (ele: RefType<any>, cls: string): any => {
   return !!ele.className.match(new RegExp("(\\s|^)" + cls + "(\\s|$)"));
 };
@@ -40,3 +42,16 @@ export const toggleClass = (
   className = className.replace(clsName, "");
   targetEl.className = flag ? `${className} ${clsName} ` : className;
 };
+
+export function useRafThrottle<T extends FunctionArgs>(fn: T): T {
+  let locked = false;
+  // @ts-ignore
+  return function (...args) {
+    if (locked) return;
+    locked = true;
+    window.requestAnimationFrame(() => {
+      fn.apply(this, args);
+      locked = false;
+    });
+  };
+}

src/utils/watermark.ts

@@ -0,0 +1,116 @@
+import {
+  ref,
+  Ref,
+  unref,
+  shallowRef,
+  onBeforeUnmount,
+  getCurrentInstance
+} from "vue";
+import { isDef } from "/@/utils/is";
+import { useRafThrottle } from "/@/utils/operate";
+import { addResizeListener, removeResizeListener } from "/@/utils/resize";
+
+const domSymbol = Symbol("watermark-dom");
+
+type attr = {
+  font?: string;
+  fillStyle?: string;
+};
+
+export function useWatermark(
+  appendEl: Ref<HTMLElement | null> = ref(document.body) as Ref<HTMLElement>
+) {
+  const func = useRafThrottle(function () {
+    const el = unref(appendEl);
+    if (!el) return;
+    const { clientHeight: height, clientWidth: width } = el;
+    updateWatermark({ height, width });
+  });
+  const id = domSymbol.toString();
+  const watermarkEl = shallowRef<HTMLElement>();
+
+  const clear = () => {
+    const domId = unref(watermarkEl);
+    watermarkEl.value = undefined;
+    const el = unref(appendEl);
+    if (!el) return;
+    domId && el.removeChild(domId);
+    removeResizeListener(el, func);
+  };
+
+  function createBase64(str: string, attr?: attr) {
+    const can = document.createElement("canvas");
+    const width = 300;
+    const height = 240;
+    Object.assign(can, { width, height });
+
+    const cans = can.getContext("2d");
+    if (cans) {
+      cans.rotate((-20 * Math.PI) / 120);
+      cans.font = attr?.font ?? "15px Reggae One";
+      cans.fillStyle = attr?.fillStyle ?? "rgba(0, 0, 0, 0.15)";
+      cans.textAlign = "left";
+      cans.textBaseline = "middle";
+      cans.fillText(str, width / 20, height);
+    }
+    return can.toDataURL("image/png");
+  }
+
+  function updateWatermark(
+    options: {
+      width?: number;
+      height?: number;
+      str?: string;
+      attr?: attr;
+    } = {}
+  ) {
+    const el = unref(watermarkEl);
+    if (!el) return;
+    if (isDef(options.width)) {
+      el.style.width = `${options.width}px`;
+    }
+    if (isDef(options.height)) {
+      el.style.height = `${options.height}px`;
+    }
+    if (isDef(options.str)) {
+      el.style.background = `url(${createBase64(
+        options.str,
+        options.attr
+      )}) left top repeat`;
+    }
+  }
+
+  const createWatermark = (str: string, attr?: attr) => {
+    if (unref(watermarkEl)) {
+      updateWatermark({ str, attr });
+      return id;
+    }
+    const div = document.createElement("div");
+    watermarkEl.value = div;
+    div.id = id;
+    div.style.pointerEvents = "none";
+    div.style.top = "0px";
+    div.style.left = "0px";
+    div.style.position = "absolute";
+    div.style.zIndex = "100000";
+    const el = unref(appendEl);
+    if (!el) return id;
+    const { clientHeight: height, clientWidth: width } = el;
+    updateWatermark({ str, width, height, attr });
+    el.appendChild(div);
+    return id;
+  };
+
+  function setWatermark(str: string, attr?: attr) {
+    createWatermark(str, attr);
+    addResizeListener(document.documentElement, func);
+    const instance = getCurrentInstance();
+    if (instance) {
+      onBeforeUnmount(() => {
+        clear();
+      });
+    }
+  }
+
+  return { setWatermark, clear };
+}