小程序海报生成海报【vue】

KIKIo_2024-03-04 15:54

文章目录

1、创建海报的基本逻辑

  • 1、先创建dom元素
    wrapperHeight是根据海报的内容计算出来海报的高度
js 复制代码 
    <view class="preview-card-wrap" @tap.stop>
      <view class="poster-box" :class="{ show: isDrew }">
        <canvas
          id="myCanvas"
          canvas-id="myCanvas"
          :style="{
            width: '750rpx',
            height: wrapperHeight + 'rpx',
          }"
        ></canvas>
      </view>
    </view>
  • 2、创建海报类
js 复制代码 
class Poster {
  canvasId: string;
  instanceComponent: ReturnType<typeof getCurrentInstance> | undefined;
  ctx: UniApp.CanvasContext | undefined = undefined;
  width = 0;
  height = 0;
  isPixel: boolean;
  drawSteps: DrawSteps = [];

  constructor(
    canvasId: string,
    instance?: ReturnType<typeof getCurrentInstance>,
    { isPixel = true } = <InitConfig>{}
  ) {
    this.canvasId = canvasId;
    this.instanceComponent = instance;
    this.ctx = uni.createCanvasContext(canvasId, instance);
    this.isPixel = isPixel;
  }
  
    /**
   * 设置画布大小
   * @param width 画布宽度
   * @param height 画布高度
   */
  public setCanvasSize(width: number, height: number) {
    this.width = width;
    this.height = height;
  }
    /**
   * 清空画布
   */
  clearAll() {
    this.ctx?.clearRect(
      0,
      0,
      this.getPixel(this.width),
      this.getPixel(this.height)
    );
    // clearRect() 方法只是将指定区域的像素设置为透明，但不会直接触发画布的重新绘制。
    // 因此，需要在清除画布后显式调用 draw() 方法，才能使清除的效果立即生效，即将空白画布展示在页面上。
    // 这个方法只是为了更新画布
    this.ctx?.draw();
  }
}


export default Poster;
  • 3、创建海报类
js 复制代码 
import { getCurrentInstance, ref } from "vue";

const poster = ref<Poster | undefined | any>(undefined);

poster.value = new Poster("myCanvas", self, { isPixel: false });

const self = getCurrentInstance();
// 设置画布大小
poster.value.setCanvasSize(750, wrapperHeight.value);
// 绘制前先清空画布
poster.value.clearAll();

2、用canvas绘制文字

  • 先将px和rpx进行转换
js 复制代码 
  /**
   * 获取大小
   * @param size
   */
  getPixel(size: number) {
    return this.isPixel ? size : rpx2px(size);
  }
  • 获取文字的宽度
js 复制代码 
  /**
   * 获取文字宽度
   * @param text 文字
   * @param fontStyle 字体样式，同 css 的 font 属性
   * @returns {number} 文字宽度
   */
  public getTextWidth(text: string, fontStyle?: string) {
    if (!this.ctx || !text.trim()) return 0;

    this.ctx.save();
    this.ctx.font = fontStyle || "14px sans-serif";
    const dimension = this.ctx.measureText(text);
    this.ctx.restore();

    return this.isPixel ? dimension.width : px2rpx(dimension.width);
  }
  • 给文字加上省略号
js 复制代码 
  // 给文字加上省略号
  public correctEllipsisText(text: string, width: number, fontStyle?: string) {
    let resultText = "";
    const strSplits = text.split("");
    while (strSplits.length > 0) {
      const s = strSplits.shift();
      const isGtWidth =
        this.getPixel(this.getTextWidth(resultText + s, fontStyle)) >
        this.getPixel(width);
      if (isGtWidth) {
        resultText = resultText.substring(0, resultText.length) + "...";
        break;
      }
      resultText += s;
    }
    return resultText;
  }
  • 绘制文字的逻辑
js 复制代码 
/**
   * 绘制文字
   * @param text 文字
   * @param x 横向绘制点
   * @param y 纵向绘制点
   * @param maxWidth 绘制区域最大宽度，文字宽度超过则换行
   * @param color 文字颜色
   * @param fontSize 文字大小
   * @param fontWeight 文字粗细
   * @param borderWidth 文字描边粗细
   * @param borderColor 文字描边样式
   * @param lineHeight 行高，即文字行与行之间的间距
   * @param UseEllipsis 当超出文字宽度是否使用省略号
   */
  public async drawText({
    text,
    x,
    y,
    maxWidth,
    color,
    fontSize,
    fontFamily,
    fontWeight = 500,
    borderWidth,
    borderColor,
    lineHeight = 1.2,
    UseEllipsis = true,
  }: TextDrawStep) {
    if (!this.ctx) return;

    const fontStyle = `${fontWeight} ${
      fontSize ? this.getPixel(fontSize) : 14
    }px ${`${fontFamily}` || "sans-serif"}`;

    this.ctx.save();

    this.ctx.setTextBaseline("top");
    this.ctx.font = fontStyle;
    color && (this.ctx.fillStyle = color);

    if (borderColor) this.ctx.strokeStyle = borderColor;

    // 绘制文字边框样式
    if (borderWidth) {
      this.ctx.lineWidth = borderWidth;
    }

    if (UseEllipsis) {
      // 将超出canvas宽度的文字用...展示
      const drawText = this.correctEllipsisText(
        text,
        maxWidth || this.width,
        fontStyle
      );

      if (borderWidth) {
        this.ctx.strokeText(
          drawText,
          this.getPixel(x),
          this.getPixel(y),
          maxWidth ? this.getPixel(maxWidth) : maxWidth
        );
      }

      this.ctx.fillText(
        drawText,
        this.getPixel(x),
        this.getPixel(y),
        maxWidth ? this.getPixel(maxWidth) : maxWidth
      );
    } else {
      // 将文本分割成数组
      const words = text.split("");
      let line = ""; // 当前行的文字内容
      let yPos = y; // 当前行的纵坐标位置

      for (let i = 0; i < words.length; i++) {
        const testLine = line + words[i]; // 当前行加上当前单词

        // 测量当前行的宽度
        const textWidth = this.getTextWidth(testLine, fontStyle);

        // 如果当前行的宽度超过最大的宽度 需要换行
        if (textWidth > this.getPixel(maxWidth || this.width)) {
          // 讲当前行绘制到canvas上
          if (borderWidth) {
            this.ctx.strokeText(
              line,
              this.getPixel(x),
              this.getPixel(y),
              maxWidth ? this.getPixel(maxWidth) : maxWidth
            );

            this.ctx.fillText(
              line,
              this.getPixel(x),
              this.getPixel(yPos),
              maxWidth ? this.getPixel(maxWidth) : maxWidth
            );

            // 开始新一行
            yPos += lineHeight * (fontSize ? this.getPixel(fontSize) : 14);
          } else {
            line = testLine;
          }
        }
      }
      this.ctx.strokeText(line, this.getPixel(x), this.getPixel(y));

      this.ctx.fillText(line, this.getPixel(x), this.getPixel(yPos));
    }

    this.ctx.restore();
  }

3、绘制矩形

js 复制代码 
  /**
   * 绘制直边形状
   * @param lines 坐标数组第一个为设置落笔点，坐标数组最后一个如果和第一个一样可省略
   * @param fillColor 填充颜色
   */
  public drawLineShape({ lines, fillColor }: LineShapeDrawStep) {
    if (!this.ctx || !lines.length) return;

    this.ctx.save();

    // 开始绘制路径
    this.ctx.beginPath();
    const [x, y] = lines[0];
    this.ctx.moveTo(this.getPixel(x), this.getPixel(y));

    // 遍历坐标数组，绘制直线段
    for (let i = 1; i < lines.length; i++) {
      const [ix, iy] = lines[i];
      this.ctx.lineTo(this.getPixel(ix), this.getPixel(iy));
    }

    if (this.ctx && fillColor) {
      this.ctx.fillStyle = fillColor;
      this.ctx.fill();
    } else {
      this.ctx.closePath();
    }

    this.ctx.restore();
  }

4、绘制圆形

js 复制代码 
  /**
   * 绘制圆形
   */
  public drawCircleShape({
    x,
    y,
    radius,
    startAngle,
    endAngle,
    anticlockwise,
    fillColor,
  }: CircleShapeDrawStep) {
    if (!this.ctx) return;

    this.ctx.save();
    this.ctx.beginPath();
    this.ctx.arc(
      this.getPixel(x),
      this.getPixel(y),
      this.getPixel(radius),
      this.getPixel(startAngle),
      this.getPixel(endAngle),
      anticlockwise
    );
    if (this.ctx && fillColor) {
      this.ctx.setFillStyle(fillColor);
      this.ctx.fill();
    } else {
      this.ctx.closePath();
    }

    this.ctx.restore();
  }

5、绘制圆角矩形

js 复制代码 
  /**
   * 绘制圆角矩形
   * @param x x坐标
   * @param y y坐标
   * @param width 宽度
   * @param height 高度
   * @param radius 圆角半径
   * @param fillColor 填充颜色
   */
  public roundRect = ({
    x,
    y,
    width,
    height,
    radius,
    fillColor,
  }: roundRectShapeDrawStep) => {
    if (!this.ctx) return;
    const dx = this.getPixel(x);
    const dy = this.getPixel(y);
    const dRadius = this.getPixel(radius);
    const dWidth = this.getPixel(width);
    const dHeight = this.getPixel(height);
    this.ctx.beginPath();
    this.ctx.moveTo(dx + dRadius, dy);
    // 下面三个点形成切线来画出圆弧
    this.ctx.lineTo(dx + dWidth - dRadius, dy);
    this.ctx.arcTo(dx + dWidth, dy, dx + dWidth, dy + dRadius, dRadius);

    this.ctx.lineTo(dx + dWidth, dy + dHeight - dRadius);
    this.ctx.arcTo(
      dx + dWidth,
      dy + dHeight,
      dx + dWidth - dRadius,
      dy + dHeight,
      dRadius
    );
    this.ctx.lineTo(dx + dRadius, dy + dHeight);
    this.ctx.arcTo(dx, dy + dHeight, dx, dy + dHeight - dRadius, dRadius);
    this.ctx.lineTo(dx, dy + dRadius);
    this.ctx.arcTo(dx, dy, dx + dRadius, dy, dRadius);
    this.ctx.closePath();
    this.ctx.fillStyle = fillColor;
    this.ctx.fill();
  };

6、绘制图片

js 复制代码 
  /**
   * 绘制图片
   * @param image 图片路径，必须为本地路径或临时路径
   * @param x 横向绘制点
   * @param y 纵向绘制点
   * @param width 绘制宽度
   * @param height 绘制高度
   * @param isCircle 是否为圆形图, 宽高需相等
   */
  public async drawImage({
    image,
    x,
    y,
    width,
    height,
    isCircle = false,
    clipConfig,
  }: ImageDrawStep) {
    if (!this.ctx) return;

    this.ctx.save();
    if (isCircle) {
      const r = Math.floor(this.getPixel(width) / 2);
      // context.arc(x, y, radius, startAngle, endAngle, anticlockwise);
      this.ctx.arc(
        this.getPixel(x) + r,
        this.getPixel(y) + r,
        r,
        0,
        2 * Math.PI
      );

      // 只有在剪切路径范围内的内容才会被保留，超出剪切路径范围的部分会被裁剪掉。
      this.ctx.clip();
    }
    await sleep(50);

    let clipParams: number[] = [];

    if (clipConfig) {
      clipParams = [
        clipConfig.x,
        clipConfig.y,
        clipConfig.width,
        clipConfig.height,
      ];
    }

    this.ctx.drawImage(
      image,
      ...clipParams,
      this.getPixel(x),
      this.getPixel(y),
      this.getPixel(width),
      this.getPixel(height)
    );
    // console.log(this.ctx, "查看图片的上下文");
    this.ctx.restore();
  }

7、执行绘制

js 复制代码 
 /**
   * 执行绘制
   */
  async draw(callback?: Function) {
    // 初始化绘图步骤数组的索引
    let index = 0;

    // 循环遍历绘图步骤数组
    while (index < this.drawSteps.length) {
      // 从当前绘图步骤中提取出类型和其他属性
      const { type, ...otherProps } = <DrawStep>this.drawSteps[index];
      const stepProps = <AnyObject>otherProps;
      const props = <AnyObject>{};

      // 合并其他属性到 props 中
      Object.assign(
        props,
        stepProps.getProps
          ? await stepProps.getProps(this.drawSteps, index)
          : stepProps
      );
      // this.drawSteps[index].drawData = {
      //   ...props,
      //   ...(this.drawSteps[index].drawData || {}),
      // };

      // 根据类型执行相应的绘图操作
      if (type === DrawType.Text) {
        await this.drawText(<TextDrawStep>props);
      } else if (type === DrawType.Image) {
        await this.drawImage(<ImageDrawStep>props);
      } else if (type === DrawType.LineShape) {
        await this.drawLineShape(<LineShapeDrawStep>props);
      } else if (type === DrawType.CircleShape) {
        await this.drawCircleShape(<CircleShapeDrawStep>props);
      } else if (type === DrawType.RoundRectShape) {
        await this.roundRect(<roundRectShapeDrawStep>props);
      }

      // 如果当前绘图步骤需要立即绘制，则执行绘图同步操作
      props.immediateDraw && (await this.syncDraw());

      // 移动到下一个绘图步骤
      index += 1;
    }

    // 执行最终的绘图操作，并在绘制完成后执行回调函数
    this.ctx?.draw(true, (res) => {
      callback?.(res);
    });
  }

8、完整的代码

js 复制代码 
import type { getCurrentInstance } from "vue";
import { px2rpx, rpx2px } from "@/utils/view";
import type {
  DrawStep,
  DrawSteps,
  ImageDrawStep,
  InitConfig,
  LineShapeDrawStep,
  TextDrawStep,
  CircleShapeDrawStep,
  roundRectShapeDrawStep,
} from "./poster";
import { DrawType } from "./poster";
import { sleep } from "@/utils";

class Poster {
  canvasId: string;
  instanceComponent: ReturnType<typeof getCurrentInstance> | undefined;
  ctx: UniApp.CanvasContext | undefined = undefined;
  width = 0;
  height = 0;
  isPixel: boolean;
  drawSteps: DrawSteps = [];

  constructor(
    canvasId: string,
    instance?: ReturnType<typeof getCurrentInstance>,
    { isPixel = true } = <InitConfig>{}
  ) {
    this.canvasId = canvasId;
    this.instanceComponent = instance;
    this.ctx = uni.createCanvasContext(canvasId, instance);
    this.isPixel = isPixel;
  }

  /**
   * 获取大小
   * @param size
   */
  getPixel(size: number) {
    return this.isPixel ? size : rpx2px(size);
  }

  public getCanvasSize() {
    return {
      width: this.width,
      height: this.height,
    };
  }

  /**
   * 设置画布大小
   * @param width 画布宽度
   * @param height 画布高度
   */
  public setCanvasSize(width: number, height: number) {
    this.width = width;
    this.height = height;
  }

  /**
   * 获取文字宽度
   * @param text 文字
   * @param fontStyle 字体样式，同 css 的 font 属性
   * @returns {number} 文字宽度
   */
  public getTextWidth(text: string, fontStyle?: string) {
    if (!this.ctx || !text.trim()) return 0;

    this.ctx.save();
    this.ctx.font = fontStyle || "14px sans-serif";
    const dimension = this.ctx.measureText(text);
    this.ctx.restore();

    return this.isPixel ? dimension.width : px2rpx(dimension.width);
  }

  // 给文字加上省略号
  public correctEllipsisText(text: string, width: number, fontStyle?: string) {
    let resultText = "";
    const strSplits = text.split("");
    while (strSplits.length > 0) {
      const s = strSplits.shift();
      const isGtWidth =
        this.getPixel(this.getTextWidth(resultText + s, fontStyle)) >
        this.getPixel(width);
      if (isGtWidth) {
        resultText = resultText.substring(0, resultText.length) + "...";
        break;
      }
      resultText += s;
    }
    return resultText;
  }

  /**
   * 绘制图片
   * @param image 图片路径，必须为本地路径或临时路径
   * @param x 横向绘制点
   * @param y 纵向绘制点
   * @param width 绘制宽度
   * @param height 绘制高度
   * @param isCircle 是否为圆形图, 宽高需相等
   */
  public async drawImage({
    image,
    x,
    y,
    width,
    height,
    isCircle = false,
    clipConfig,
  }: ImageDrawStep) {
    if (!this.ctx) return;

    this.ctx.save();
    if (isCircle) {
      const r = Math.floor(this.getPixel(width) / 2);
      // context.arc(x, y, radius, startAngle, endAngle, anticlockwise);
      this.ctx.arc(
        this.getPixel(x) + r,
        this.getPixel(y) + r,
        r,
        0,
        2 * Math.PI
      );

      // 只有在剪切路径范围内的内容才会被保留，超出剪切路径范围的部分会被裁剪掉。
      this.ctx.clip();
    }
    await sleep(50);

    let clipParams: number[] = [];

    if (clipConfig) {
      clipParams = [
        clipConfig.x,
        clipConfig.y,
        clipConfig.width,
        clipConfig.height,
      ];
    }

    this.ctx.drawImage(
      image,
      ...clipParams,
      this.getPixel(x),
      this.getPixel(y),
      this.getPixel(width),
      this.getPixel(height)
    );
    // console.log(this.ctx, "查看图片的上下文");
    this.ctx.restore();
  }

  /**
   * 绘制文字
   * @param text 文字
   * @param x 横向绘制点
   * @param y 纵向绘制点
   * @param maxWidth 绘制区域最大宽度，文字宽度超过则换行
   * @param color 文字颜色
   * @param fontSize 文字大小
   * @param fontWeight 文字粗细
   * @param borderWidth 文字描边粗细
   * @param borderColor 文字描边样式
   * @param lineHeight 行高，即文字行与行之间的间距
   * @param UseEllipsis 当超出文字宽度是否使用省略号
   */
  public async drawText({
    text,
    x,
    y,
    maxWidth,
    color,
    fontSize,
    fontFamily,
    fontWeight = 500,
    borderWidth,
    borderColor,
    lineHeight = 1.2,
    UseEllipsis = true,
  }: TextDrawStep) {
    if (!this.ctx) return;

    const fontStyle = `${fontWeight} ${
      fontSize ? this.getPixel(fontSize) : 14
    }px ${`${fontFamily}` || "sans-serif"}`;

    this.ctx.save();

    this.ctx.setTextBaseline("top");
    this.ctx.font = fontStyle;
    color && (this.ctx.fillStyle = color);

    if (borderColor) this.ctx.strokeStyle = borderColor;

    // 绘制文字边框样式
    if (borderWidth) {
      this.ctx.lineWidth = borderWidth;
    }

    if (UseEllipsis) {
      // 将超出canvas宽度的文字用...展示
      const drawText = this.correctEllipsisText(
        text,
        maxWidth || this.width,
        fontStyle
      );

      if (borderWidth) {
        this.ctx.strokeText(
          drawText,
          this.getPixel(x),
          this.getPixel(y),
          maxWidth ? this.getPixel(maxWidth) : maxWidth
        );
      }

      this.ctx.fillText(
        drawText,
        this.getPixel(x),
        this.getPixel(y),
        maxWidth ? this.getPixel(maxWidth) : maxWidth
      );
    } else {
      // 将文本分割成数组
      const words = text.split("");
      let line = ""; // 当前行的文字内容
      let yPos = y; // 当前行的纵坐标位置

      for (let i = 0; i < words.length; i++) {
        const testLine = line + words[i]; // 当前行加上当前单词

        // 测量当前行的宽度
        const textWidth = this.getTextWidth(testLine, fontStyle);

        // 如果当前行的宽度超过最大的宽度 需要换行
        if (textWidth > this.getPixel(maxWidth || this.width)) {
          // 讲当前行绘制到canvas上
          if (borderWidth) {
            this.ctx.strokeText(
              line,
              this.getPixel(x),
              this.getPixel(y),
              maxWidth ? this.getPixel(maxWidth) : maxWidth
            );

            this.ctx.fillText(
              line,
              this.getPixel(x),
              this.getPixel(yPos),
              maxWidth ? this.getPixel(maxWidth) : maxWidth
            );

            // 开始新一行
            yPos += lineHeight * (fontSize ? this.getPixel(fontSize) : 14);
          } else {
            line = testLine;
          }
        }
      }
      this.ctx.strokeText(line, this.getPixel(x), this.getPixel(y));

      this.ctx.fillText(line, this.getPixel(x), this.getPixel(yPos));
    }

    this.ctx.restore();
  }

  /**
   * 绘制直边形状
   * @param lines 坐标数组第一个为设置落笔点，坐标数组最后一个如果和第一个一样可省略
   * @param fillColor 填充颜色
   */
  public drawLineShape({ lines, fillColor, gradients }: LineShapeDrawStep) {
    if (!this.ctx || !lines.length) return;

    this.ctx.save();

    this.ctx.beginPath();
    const [x, y] = lines[0];
    this.ctx.moveTo(this.getPixel(x), this.getPixel(y));

    for (let i = 1; i < lines.length; i++) {
      const [ix, iy] = lines[i];
      this.ctx.lineTo(this.getPixel(ix), this.getPixel(iy));
    }

    if (this.ctx && fillColor) {
      this.ctx.fillStyle = fillColor;
      this.ctx.fill();
    } else if (this.ctx && gradients?.length) {
      var lineargradient = this.ctx.createLinearGradient(
        gradients[0],
        gradients[1],
        gradients[2],
        gradients[3]
      );
      lineargradient.addColorStop(0, "#363636");
      lineargradient.addColorStop(1, "white");
      this.ctx.setFillStyle(lineargradient);
      this.ctx.fill();
    } else {
      this.ctx.closePath();
    }

    this.ctx.restore();
  }

  /**
   * 绘制圆形
   */
  public drawCircleShape({
    x,
    y,
    radius,
    startAngle,
    endAngle,
    anticlockwise,
    fillColor,
  }: CircleShapeDrawStep) {
    if (!this.ctx) return;

    this.ctx.save();
    this.ctx.beginPath();
    this.ctx.arc(
      this.getPixel(x),
      this.getPixel(y),
      this.getPixel(radius),
      this.getPixel(startAngle),
      this.getPixel(endAngle),
      anticlockwise
    );
    if (this.ctx && fillColor) {
      this.ctx.setFillStyle(fillColor);
      this.ctx.fill();
    } else {
      this.ctx.closePath();
    }

    this.ctx.restore();
  }

  syncDraw(): Promise<void> {
    return new Promise((resolve) => {
      this.ctx?.draw(true, async () => {
        await sleep(30);
        resolve();
      });
    });
  }

  /**
   * 绘制圆角矩形
   * @param x x坐标
   * @param y y坐标
   * @param width 宽度
   * @param height 高度
   * @param radius 圆角半径
   * @param fillColor 填充颜色
   */
  public roundRect = ({
    x,
    y,
    width,
    height,
    radius,
    fillColor,
  }: roundRectShapeDrawStep) => {
    if (!this.ctx) return;
    const dx = this.getPixel(x);
    const dy = this.getPixel(y);
    const dRadius = this.getPixel(radius);
    const dWidth = this.getPixel(width);
    const dHeight = this.getPixel(height);
    this.ctx.beginPath();
    this.ctx.moveTo(dx + dRadius, dy);
    // 下面三个点形成切线来画出圆弧
    this.ctx.lineTo(dx + dWidth - dRadius, dy);
    this.ctx.arcTo(dx + dWidth, dy, dx + dWidth, dy + dRadius, dRadius);

    this.ctx.lineTo(dx + dWidth, dy + dHeight - dRadius);
    this.ctx.arcTo(
      dx + dWidth,
      dy + dHeight,
      dx + dWidth - dRadius,
      dy + dHeight,
      dRadius
    );
    this.ctx.lineTo(dx + dRadius, dy + dHeight);
    this.ctx.arcTo(dx, dy + dHeight, dx, dy + dHeight - dRadius, dRadius);
    this.ctx.lineTo(dx, dy + dRadius);
    this.ctx.arcTo(dx, dy, dx + dRadius, dy, dRadius);
    this.ctx.closePath();
    this.ctx.fillStyle = fillColor;
    this.ctx.fill();
  };

  /**
   * 执行绘制
   */
  async draw(callback?: Function) {
    // 初始化绘图步骤数组的索引
    let index = 0;

    // 循环遍历绘图步骤数组
    while (index < this.drawSteps.length) {
      // 从当前绘图步骤中提取出类型和其他属性
      const { type, ...otherProps } = <DrawStep>this.drawSteps[index];
      const stepProps = <AnyObject>otherProps;
      const props = <AnyObject>{};

      // 合并其他属性到 props 中
      Object.assign(
        props,
        stepProps.getProps
          ? await stepProps.getProps(this.drawSteps, index)
          : stepProps
      );
      // this.drawSteps[index].drawData = {
      //   ...props,
      //   ...(this.drawSteps[index].drawData || {}),
      // };

      // 根据类型执行相应的绘图操作
      if (type === DrawType.Text) {
        await this.drawText(<TextDrawStep>props);
      } else if (type === DrawType.Image) {
        await this.drawImage(<ImageDrawStep>props);
      } else if (type === DrawType.LineShape) {
        await this.drawLineShape(<LineShapeDrawStep>props);
      } else if (type === DrawType.CircleShape) {
        await this.drawCircleShape(<CircleShapeDrawStep>props);
      } else if (type === DrawType.RoundRectShape) {
        await this.roundRect(<roundRectShapeDrawStep>props);
      }

      // 如果当前绘图步骤需要立即绘制，则执行绘图同步操作
      props.immediateDraw && (await this.syncDraw());

      // 移动到下一个绘图步骤
      index += 1;
    }

    // 执行最终的绘图操作，并在绘制完成后执行回调函数
    this.ctx?.draw(true, (res) => {
      callback?.(res);
    });
  }

  /**
   * 将绘制内容转成图片
   * @returns {Promise<string>} 图片临时路径
   */
  canvas2Image(): Promise<UniApp.CanvasToTempFilePathRes> | undefined {
    if (!this.ctx) return;
    return new Promise((resolve) => {
      uni.canvasToTempFilePath(
        {
          canvasId: this.canvasId,
          x: 0,
          y: 0,
          width: this.width,
          height: this.height,
          success: resolve,
        },
        this.instanceComponent
      );
    });
  }

  /**
   * 清空画布
   */
  clearAll() {
    this.ctx?.clearRect(
      0,
      0,
      this.getPixel(this.width),
      this.getPixel(this.height)
    );
    // clearRect() 方法只是将指定区域的像素设置为透明，但不会直接触发画布的重新绘制。
    // 因此，需要在清除画布后显式调用 draw() 方法，才能使清除的效果立即生效，即将空白画布展示在页面上。
    // 这个方法只是为了更新画布
    this.ctx?.draw();
  }
}

export default Poster;
js 复制代码 
export enum DrawType {
  Text = "text",
  Image = "image",
  LineShape = "lineShape",
  CircleShape = "circleShape",
  RoundRectShape = "roundRectShape",
}

export interface InitConfig {
  isPixel: boolean;
}

export type BaseDrawStep = {
  x: number;
  y: number;
};

export type GetProps<O> = {
  getProps: (steps: DrawSteps, index: number) => O | Promise<O>;
};

export type TextDrawStep = BaseDrawStep & {
  text: string;
  maxWidth?: number;
  color?: string;
  fontSize?: number;
  fontFamily?: string;
  fontWeight?: number;
  borderWidth?: number;
  borderColor?: string;
  lineHeight?: number;
  UseEllipsis?: boolean;
};

export type ImageDrawStep = BaseDrawStep & {
  image: string;
  width: number;
  height: number;
  isCircle?: boolean;
  clipConfig?: {
    x: number;
    y: number;
    width: number;
    height: number;
  };
};

export type LineShapeDrawStep = {
  lines: Array<[number, number]>;
  fillColor?: string;
  strokeStyle?: string;
  gradients?: Array<number>;
};
export type CircleShapeDrawStep = {
  x: number;
  y: number;
  radius: number;
  startAngle: number;
  endAngle: number;
  anticlockwise: boolean;
  fillColor?: string;
};

export type roundRectShapeDrawStep = {
  ctx: CanvasRenderingContext2D;
  x: number;
  y: number;
  width: number;
  height: number;
  radius: number;
  fillColor: any;
};

export type DrawStep =
  | ({ type: DrawType.Text } & (TextDrawStep | GetProps<TextDrawStep>))
  | ({ type: DrawType.Image } & (ImageDrawStep | GetProps<ImageDrawStep>))
  | ({ type: DrawType.LineShape } & (
      | LineShapeDrawStep
      | GetProps<LineShapeDrawStep>
    ));

export type DrawSteps = Array<
  DrawStep & { drawData?: AnyObject; immediateDraw?: boolean }
>;
js 复制代码 
export const px2rpx = (px: number) => px / (uni.upx2px(100) / 100);
export const rpx2px = (rpx: number) => uni.upx2px(rpx);
  • 使用
js 复制代码 
import { getCurrentInstance, ref } from "vue";

const poster = ref<Poster | undefined | any>(undefined);

poster.value = new Poster("myCanvas", self, { isPixel: false });

const self = getCurrentInstance();
// 设置画布大小
poster.value.setCanvasSize(750, wrapperHeight.value);
// 绘制前先清空画布
poster.value.clearAll();
poster.value.drawSteps = [
   {
   // 背景高斯模糊图片
     type: DrawType.Image,
     getProps: (steps: DrawSteps) => {
      return {
        image: flurBg.path,
        x: 0,
        y: 0,
        width: 750,
        height: 308,
      };
    },
  },  
];

 await poster.value.draw((res: any) => {
    uni.hideLoading();
 });
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