CommunityApp/pagesM/comps/canvas/index.vue

<template>
  <view class="container">
    <canvas canvas-id="canvasid" class="dt-canvas" :class="debug ? 'debug' : 'pro'" :style="'width:'+pxWidth+'px;height:'+pxHeight+'px;'"></canvas>
  </view>
</template>
<script>

export default {
  data() {
    return {
      ctx: {},
      factor: 0,
      pxHeight: 0,
      pxWidth: 0,
    };
  },

  methods: {
    /**
      * 计算画布的高度
      * @param {*} config
      */
    getHeight(config) {
      const getTextHeight = text => {
        let fontHeight = text.lineHeight || text.fontSize;
        let height = 0;
        if (text.baseLine === "top") {
          height = fontHeight;
        } else if (text.baseLine === "middle") {
          height = fontHeight / 2;
        } else {
          height = 0;
        }
        return height;
      };
      const heightArr = [];
      (config.blocks || []).forEach(item => {
        heightArr.push(item.y + item.height);
      });
      (config.texts || []).forEach(item => {
        let height;
        if (Object.prototype.toString.call(item.text) === "[object Array]") {
          item.text.forEach(i => {
            height = getTextHeight({ ...i, baseLine: item.baseLine });
            heightArr.push(item.y + height);
          });
        } else {
          height = getTextHeight(item);
          heightArr.push(item.y + height);
        }
      });
      (config.images || []).forEach(item => {
        heightArr.push(item.y + item.height);
      });
      (config.lines || []).forEach(item => {
        heightArr.push(item.startY);
        heightArr.push(item.endY);
      });
      const sortRes = heightArr.sort((a, b) => b - a);
      let canvasHeight = 0;
      if (sortRes.length > 0) {
        canvasHeight = sortRes[0];
      }
      if (config.height < canvasHeight || !config.height) {
        return canvasHeight;
      } else {
        return config.height;
      }
    },
    create(config) {
      this.ctx = uni.createCanvasContext("canvasid", this);
      const height = this.getHeight(config);
      this.initCanvas(config.width, height, config.debug)
        .then(() => {
          // 设置画布底色
          if (config.backgroundColor) {
            this.ctx.save();
            this.ctx.setFillStyle(config.backgroundColor);
            this.ctx.fillRect(
              0,
              0,
              this.toPx(config.width),
              this.toPx(height)
            );
            this.ctx.restore();
          }
          const { texts = [], images = [], blocks = [], lines = [] } = config;
          const queue = this.drawArr
            .concat(
              texts.map(item => {
                item.type = "text";
                item.zIndex = item.zIndex || 0;
                return item;
              })
            )
            .concat(
              blocks.map(item => {
                item.type = "block";
                item.zIndex = item.zIndex || 0;
                return item;
              })
            )
            .concat(
              lines.map(item => {
                item.type = "line";
                item.zIndex = item.zIndex || 0;
                return item;
              })
            );
          // 按照顺序排序
          queue.sort((a, b) => a.zIndex - b.zIndex);

          queue.forEach(item => {
            if (item.type === "image") {
              this.drawImage(item);
            } else if (item.type === "text") {
              this.drawText(item);
            } else if (item.type === "block") {
              this.drawBlock(item);
            } else if (item.type === "line") {
              this.drawLine(item);
            }
          });

          const res = uni.getSystemInfoSync();
          const platform = res.platform;
          let time = 0;
          if (platform === "android") {
            // 在安卓平台，经测试发现如果海报过于复杂在转换时需要做延时，要不然样式会错乱
            time = 300;
          }
          this.ctx.draw(false, () => {
            setTimeout(() => {
              uni.canvasToTempFilePath(
                {
                  canvasId: "canvasid",
                  success: res => {
                    this.$emit("success", res.tempFilePath);
                  },
                  fail: err => {
                    this.$emit("fail", err);
                  }
                },
                this
              );
            }, time);
          });
        })
        .catch(err => {
          uni.showToast({ icon: "none", title: err.errMsg || "生成失败" });
          console.error(err);
        });
    },

    /**  
     * main
     -----------------------*/
    /**
     * 渲染块
     * @param {Object} params
     */
    drawBlock({ text, width = 0, height, x, y, paddingLeft = 0, paddingRight = 0, borderWidth, backgroundColor, borderColor, borderRadius = 0, opacity = 1 }) {
      // 判断是否块内有文字
      let blockWidth = 0; // 块的宽度
      let textX = 0;
      let textY = 0;
      if (typeof text !== 'undefined') {
        // 如果有文字并且块的宽度小于文字宽度，块的宽度为 文字的宽度 + 内边距
        const textWidth = this._getTextWidth(typeof text.text === 'string' ? text : text.text);
        blockWidth = textWidth > width ? textWidth : width;
        blockWidth += paddingLeft + paddingLeft;
        x=x-blockWidth/2
        const { textAlign = 'left', text: textCon } = text;
        textY = height/2+ y; // 文字的y轴坐标在块中线
        if (textAlign === 'left') {
          // 如果是右对齐，那x轴在块的最左边
          textX = x + paddingLeft;
        } else if (textAlign === 'center') {
          textX = blockWidth / 2 + x;
        } else {
          textX = x + blockWidth - paddingRight;
        }
      } else {
        blockWidth = width;
      }

      if (backgroundColor) {
        // 画面
        this.ctx.save();
        this.ctx.setGlobalAlpha(opacity);
        this.ctx.setFillStyle(backgroundColor);
        if (borderRadius > 0) {
          // 画圆角矩形
          this._drawRadiusRect(x, y, blockWidth, height, borderRadius);
          this.ctx.fill();
        } else {
          this.ctx.fillRect(this.toPx(x), this.toPx(y), this.toPx(blockWidth), this.toPx(height));
        }
        this.ctx.restore();
      }
      if (borderWidth) {
        // 画线
        this.ctx.save();
        this.ctx.setGlobalAlpha(opacity);
        this.ctx.setStrokeStyle(borderColor);
        this.ctx.setLineWidth(this.toPx(borderWidth));
        if (borderRadius > 0) {
          // 画圆角矩形边框
          this._drawRadiusRect(x, y, blockWidth, height, borderRadius);
          this.ctx.stroke();
        } else {
          this.ctx.strokeRect(this.toPx(x), this.toPx(y), this.toPx(blockWidth), this.toPx(height));
        }
        this.ctx.restore();
      }

      if (text) {
        this.drawText(Object.assign(text, { x: textX, y: textY }))
      }
    },

    /**
     * 渲染文字
     * @param {Object} params
     */
    drawText(params) {
      const { x, y, fontSize, color, baseLine, textAlign, text, opacity = 1, width, lineNum, lineHeight } = params;
      if (Object.prototype.toString.call(text) === '[object Array]') {
        let preText = { x, y, baseLine };
        text.forEach(item => {
          preText.x += item.marginLeft || 0;
          const textWidth = this._drawSingleText(Object.assign(item, {
            ...preText,
          }));
          preText.x += textWidth + (item.marginRight || 0); // 下一段字的x轴为上一段字x + 上一段字宽度
        })
      } else {
        this._drawSingleText(params);
      }
    },

    /**
     * 渲染图片
     */
    drawImage(data) {
      const { imgPath, x, y, w, h, sx, sy, sw, sh, borderRadius = 0, borderWidth = 0, borderColor } = data;
      this.ctx.save();
      if (borderRadius > 0) {
        this.ctx.setFillStyle("#FFF");
        this._drawRadiusRect(x, y, w, h, borderRadius);
        this.ctx.fill();
        this.ctx.clip();
        this.ctx.drawImage(imgPath, this.toPx(sx), this.toPx(sy), this.toPx(sw), this.toPx(sh), this.toPx(x), this.toPx(y), this.toPx(w), this.toPx(h));
        if (borderWidth > 0) {
          this.ctx.setStrokeStyle(borderColor);
          this.ctx.setLineWidth(this.toPx(borderWidth));
          this.ctx.stroke();
        }
      } else {
        this.ctx.drawImage(imgPath, this.toPx(sx), this.toPx(sy), this.toPx(sw), this.toPx(sh), this.toPx(x), this.toPx(y), this.toPx(w), this.toPx(h));
      }
      this.ctx.restore();
    },
    /**
     * 渲染线
     * @param {*} param0
     */
    drawLine({ startX, startY, endX, endY, color, width }) {
      this.ctx.save();
      this.ctx.beginPath();
      this.ctx.setStrokeStyle(color);
      this.ctx.setLineWidth(this.toPx(width));
      this.ctx.moveTo(this.toPx(startX), this.toPx(startY));
      this.ctx.lineTo(this.toPx(endX), this.toPx(endY));
      this.ctx.stroke();
      this.ctx.closePath();
      this.ctx.restore();
    },
    downloadResource(images = []) {
      const drawList = [];
      this.drawArr = [];
      images.forEach((image, index) => drawList.push(this._downloadImageAndInfo(image, index)));
      return Promise.all(drawList);
    },
    initCanvas(w, h, debug) {
      return new Promise((resolve) => {
        this.pxWidth = this.toPx(w)
        this.pxHeight = this.toPx(h)
        this.debug = debug
        setTimeout(() => {
          resolve()
        }, 0)
      });
    },

    /**  
     * handle
     -----------------------*/
    /**
     * 画圆角矩形
     */
    _drawRadiusRect(x, y, w, h, r) {
      const br = r / 2;
      this.ctx.beginPath();
      this.ctx.moveTo(this.toPx(x + br), this.toPx(y));    // 移动到左上角的点
      this.ctx.lineTo(this.toPx(x + w - br), this.toPx(y));
      this.ctx.arc(this.toPx(x + w - br), this.toPx(y + br), this.toPx(br), 2 * Math.PI * (3 / 4), 2 * Math.PI * (4 / 4))
      this.ctx.lineTo(this.toPx(x + w), this.toPx(y + h - br));
      this.ctx.arc(this.toPx(x + w - br), this.toPx(y + h - br), this.toPx(br), 0, 2 * Math.PI * (1 / 4))
      this.ctx.lineTo(this.toPx(x + br), this.toPx(y + h));
      this.ctx.arc(this.toPx(x + br), this.toPx(y + h - br), this.toPx(br), 2 * Math.PI * (1 / 4), 2 * Math.PI * (2 / 4))
      this.ctx.lineTo(this.toPx(x), this.toPx(y + br));
      this.ctx.arc(this.toPx(x + br), this.toPx(y + br), this.toPx(br), 2 * Math.PI * (2 / 4), 2 * Math.PI * (3 / 4))
    },
    /**
     * 计算文本长度
     * @param {Array|Object}} text 数组 或者 对象
     */
    _getTextWidth(text) {
      let texts = [];
      if (Object.prototype.toString.call(text) === '[object Object]') {
        texts.push(text);
      } else {
        texts = text;
      }
      let width = 0;
      texts.forEach(({ fontSize, text, marginLeft = 0, marginRight = 0 }) => {
        this.ctx.setFontSize(this.toPx(fontSize));
        width += this.ctx.measureText(text).width + marginLeft + marginRight;
      })

      return this.toRpx(width);
    },
    /**
     * 渲染一段文字
     */
    _drawSingleText({ x, y, fontSize, color, baseLine, textAlign = 'left', text, opacity = 1, textDecoration = 'none',
      width, lineNum = 1, lineHeight = 0, fontWeight = 'normal', fontStyle = 'normal', fontFamily = "sans-serif" }) {
      this.ctx.save();
      this.ctx.beginPath();
      this.ctx.font = fontStyle + " " + fontWeight + " " + this.toPx(fontSize, true) + "px " + fontFamily
      this.ctx.setGlobalAlpha(opacity);
      // this.ctx.setFontSize(this.toPx(fontSize));
      this.ctx.setFillStyle(color);
      this.ctx.setTextBaseline(baseLine);
      this.ctx.setTextAlign(textAlign);
      let textWidth = this.toRpx(this.ctx.measureText(text).width);
      const textArr = [];
      if (textWidth > width) {
        // 文本宽度 大于 渲染宽度
        let fillText = '';
        let line = 1;
        for (let i = 0; i <= text.length - 1; i++) {  // 将文字转为数组，一行文字一个元素
          fillText = fillText + text[i];
          if (this.toRpx(this.ctx.measureText(fillText).width) >= width) {
            if (line === lineNum) {
              if (i !== text.length - 1) {
                fillText = fillText.substring(0, fillText.length - 1) + '...';
              }
            }
            if (line <= lineNum) {
              textArr.push(fillText);
            }
            fillText = '';
            line++;
          } else {
            if (line <= lineNum) {
              if (i === text.length - 1) {
                textArr.push(fillText);
              }
            }
          }
        }
        textWidth = width;
      } else {
        textArr.push(text);
      }

      textArr.forEach((item, index) => {
        this.ctx.fillText(item, this.toPx(x), this.toPx(y + (lineHeight || fontSize) * index));
      })

      this.ctx.restore();

      // textDecoration
      if (textDecoration !== 'none') {
        let lineY = y;
        if (textDecoration === 'line-through') {
          // 目前只支持贯穿线
          lineY = y;
        }
        this.ctx.save();
        this.ctx.moveTo(this.toPx(x), this.toPx(lineY));
        this.ctx.lineTo(this.toPx(x) + this.toPx(textWidth), this.toPx(lineY));
        this.ctx.setStrokeStyle(color);
        this.ctx.stroke();
        this.ctx.restore();
      }

      return textWidth;
    },


    /**  
     * helper
     -----------------------*/
    /**
     * 下载图片并获取图片信息
     */
    _downloadImageAndInfo(image, index) {
      return new Promise((resolve, reject) => {
        const { x, y, url, zIndex, type } = image;
        const imageUrl = url;
	
        // 下载图片
        this._downImage(imageUrl, index, type)
          // 获取图片信息
          .then(imgPath => this._getImageInfo(imgPath, index))
          .then(({ imgPath, imgInfo }) => {
            // 根据画布的宽高计算出图片绘制的大小，这里会保证图片绘制不变形
            let sx;
            let sy;
            const borderRadius = image.borderRadius || 0;
            const setWidth = image.width;
            const setHeight = image.height;
            const width = this.toRpx(imgInfo.width);
            const height = this.toRpx(imgInfo.height);
            if (width / height <= setWidth / setHeight) {
              sx = 0;
              sy = (height - ((width / setWidth) * setHeight)) / 2;
            } else {
              sy = 0;
              sx = (width - ((height / setHeight) * setWidth)) / 2;
            }
            this.drawArr.push({
              type: 'image',
              borderRadius,
              borderWidth: image.borderWidth,
              borderColor: image.borderColor,
              zIndex: typeof zIndex !== 'undefined' ? zIndex : index,
              imgPath,
              sx,
              sy,
              sw: (width - (sx * 2)),
              sh: (height - (sy * 2)),
              x,
              y,
              w: setWidth,
              h: setHeight,
            });
            resolve();
          })
          .catch(err => reject(err));
      });
    },
    /**
     * 下载图片资源
     * @param {*} imageUrl
     */
    _downImage(imageUrl,index,type) {
      return new Promise((resolve, reject) => {
        if (/^http/.test(imageUrl) && !new RegExp(wx.env.USER_DATA_PATH).test(imageUrl)&&type!=='qrcode') {
          wx.downloadFile({
            url: this._mapHttpToHttps(imageUrl),
            success: (res) => {
              if (res.statusCode === 200) {
                resolve(res.tempFilePath);
              } else {
                reject(res.errMsg);
              }
            },
            fail(err) {
              reject(err);
            },
          });
        } else {
          // 支持本地地址
          resolve(imageUrl);
        }
      });
    },
    /**
     * 获取图片信息
     * @param {*} imgPath
     * @param {*} index
     */
    _getImageInfo(imgPath, index) {
      return new Promise((resolve, reject) => {
        wx.getImageInfo({
          src: imgPath,
          success(res) {
            resolve({ imgPath, imgInfo: res, index });
          },
          fail(err) {
            reject(err);
          },
        });
      });
    },
    toPx(rpx, int) {
      // console.log('toPx',this.factor)
      if (int) {
        return parseInt(rpx * this.factor);
      }
      return rpx * this.factor;
    },
    toRpx(px, int) {
      // console.log('toRpx',this.factor)

      if (int) {
        return parseInt(px / this.factor);
      }
      return px / this.factor;
    },
    /**
     * 将http转为https
     * @param {String}} rawUrl 图片资源url
     */
    _mapHttpToHttps(rawUrl) {
      if (rawUrl.indexOf(':') < 0) {
        return rawUrl;
      }
      const urlComponent = rawUrl.split(':');
      if (urlComponent.length === 2) {
        if (urlComponent[0] === 'http') {
          urlComponent[0] = 'https';
          return `${urlComponent[0]}:${urlComponent[1]}`;
        }
      }
      return rawUrl;
    },
  },
  created() {
    const sysInfo = uni.getSystemInfoSync();
    const screenWidth = sysInfo.screenWidth;
    this.factor = screenWidth / 750;
    // console.log('created')
  },
};
</script>

<style lang="scss">
.dt-canvas {
  width: 750upx;
  height: 750upx;
}
.dt-canvas.pro {
  position: absolute;
  bottom: 0;
  left: 0;
  transform: translate3d(-9999upx, 0, 0);
}
.dt-canvas.debug {
  position: absolute;
  bottom: 0;
  left: 0;
  border: 1upx solid #ccc;
}
</style>