smallexecanvas/index/drawCanvas.js

class DrawCanvas {

  constructor() {
    this._ctx = null
    this._canvas = null
    this._executionArr = []
    this._pathArr = []
    this._style = null
    this._matrix = null
  }

  _init({ width, height, canvas, dicTypePath = '', callBack }) {
    if (!width || !height || !canvas) return
    const ctx = canvas.getContext('2d')
    canvas.width = width
    canvas.height = height
    this._canvas = canvas
    this._ctx = ctx
    this._matrix = ctx.getTransform() //矩阵
    this._executionArr = [] //每移动一笔的数据
    this._pathArr = [] //抬起落下为一笔
    // 添加路径底图 
    const path = this.sPath2cPath(dicTypePath)
    if (path) {
      this._ctx.stroke(path)
      this._ctx.clip(path) //IOS 下裁切后无法继续画图
    }
    callBack()
    console.log('初始化完成');
  }

  mouseStart() {
    console.log('开始移动');
    this._executionArr = []
  }

  mouseMove({ x = 0, y = 0 }) {
    if (!this._style || !this._style.fillStyle) return
    console.log('移动中');
    this._executionArr.push([x, y])
    this._ctx.fillStyle = this._style.fillStyle
    const X = x - (this._style.w / 2)
    const Y = y - (this._style.h / 2)
    this._ctx.fillRect(X, Y, this._style.w, this._style.h)
  }

  mouseEnd() {
    if (!this._style || !this._style.fillStyle) return
    console.log('移动结束');
    this._pathArr.push({
      fillStyle: this._style,
      path: this._executionArr
    })
  }

  mouseBack() {
    // 删除每个移动数据
    if (!this._pathArr.length || !this._ctx) return
    // 清空画布
    this._ctx.clearRect(0, 0, this._ctx.canvas.width, this._ctx.canvas.height)
    this._pathArr.pop()
    // 重画
    for (let k = 0; k < this._pathArr.length; k++) {
      const el = this._pathArr[k];
      for (let j = 0; j < el.path.length; j++) {
        const es = el.path[j];
        this._ctx.fillStyle = el.style.fillStyle
        const X = es[0] - (el.style.w / 2)
        const Y = es[1] - (el.style.h / 2)
        this._ctx.fillRect(X, Y, el.style.w, el.style.h)
      }
    }
  }

  // 切换画笔
  changeBrush({ url = '', w = 10, h = 10, angle = 0 }) {
    if (!url || !this._ctx || !this._canvas) return
    const img = this._canvas.createImage()
    img.src = url
    img.onload = () => {
      const fillStyle = this._ctx.createPattern(img, 'repeat')
      console.log('画笔样式', fillStyle);
      // 旋转 + 矩阵变化
      if (angle && this._matrix) {
        this._matrix.rotateSelf(angle)
        fillStyle.setTransform(this._matrix)
      }
      this._style = { fillStyle, w, h }
    }
  }

  // svg 路径转 canvas 路径
  sPath2cPath(path = '') {
    if (!path || !this._canvas) return null
    const arr = path.split(/(^|\s+)(?=[A-Z])/).filter(el => el !== ' ')
    const PATH = this._canvas.createPath2D();
    for (let k = 0; k < arr.length; k++) {
      const el = arr[k].replace(/\s+/g, ',');
      const key = el.replace(/[^A-Z]/g, '')
      const value = el.replace(/[A-Z]/g, '').split(',')
      if (key === 'M') {
        PATH.moveTo(value[0], value[1]);
      } else if (key === 'C') {
        PATH.bezierCurveTo(value[0], value[1], value[2], value[3], value[4], value[5]);
      } else if (key === 'L') {
        PATH.lineTo(value[0], value[1]);
      }
    }
    return PATH
  }

  // 清除画布
  clear() {
    if (!this._ctx) return
    // 清空画布
    this._ctx.clearRect(0, 0, this._ctx.canvas.width, this._ctx.canvas.height)
    // 清除路径数据
    this._pathArr = []
    this._executionArr = []
  }

  // 销毁
  destory() {
    this._ctx = null
    this._canvas = null
    this._executionArr = []
    this._pathArr = []
    this._style = null
    this._matrix = null
  }

  // 保存
  save(callBack) {
    if (!this._canvas) return callBack('')
    wx.canvasToTempFilePath({
      canvas: this._canvas,
      success(res) {
        callBack(res)
      }
    })
  }
}

export { DrawCanvas }