/*
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需求：给整个页面添加背景水印。
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思路：
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1、使用 canvas 特性生成 base64 格式的图片文件，设置其字体大小，颜色等。
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2、将其设置为背景图片，从而实现页面或组件水印效果
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使用：设置水印文案，颜色，字体大小即可
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<div v-waterMarker="{text:'版权所有',textColor:'rgba(180, 180, 180, 0.4)'}"></div>
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*/
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import type { Directive, DirectiveBinding } from "vue";
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const addWaterMarker: Directive = (str: string, parentNode: any, font: any, textColor: string) => {
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// 水印文字，父元素，字体，文字颜色
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let can: HTMLCanvasElement = document.createElement("canvas");
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parentNode.appendChild(can);
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can.width = 205;
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can.height = 140;
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can.style.display = "none";
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let cans = can.getContext("2d") as CanvasRenderingContext2D;
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cans.rotate((-20 * Math.PI) / 180);
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cans.font = font || "16px Microsoft JhengHei";
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cans.fillStyle = textColor || "rgba(180, 180, 180, 0.3)";
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cans.textAlign = "left";
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cans.textBaseline = "Middle" as CanvasTextBaseline;
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cans.fillText(str, can.width / 10, can.height / 2);
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parentNode.style.backgroundImage = "url(" + can.toDataURL("image/png") + ")";
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};
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const waterMarker = {
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mounted(el: DirectiveBinding, binding: DirectiveBinding) {
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addWaterMarker(binding.value.text, el, binding.value.font, binding.value.textColor);
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}
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};
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export default waterMarker;
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