获取画布信息并绘制背景

.whml

<canvas class="canvas" type="2d" id="myCanvas" bindtouchstart="get_rect_touch_position" bindtouchmove="move_or_scale" bind:tap="finish_edit_check"/>

.wxss

.canvas{background-color: white;height: 65vh;width: 100%;margin-top: 5px;margin-bottom: 5px;  
}

 .js

获取画布对象并设置背景图

onReady() {const query = wx.createSelectorQuery()query.select('#myCanvas').fields({ node: true, size: true }).exec((res) => {const canvas = res[0].nodeconst ctx = canvas.getContext('2d')const dpr = wx.getSystemInfoSync().pixelRatiothis.setData({pixelRatio: dpr})canvas.width = res[0].width * dprcanvas.height = res[0].height * dpr      var bg = canvas.createImage()var bg_info = {img: bg,width: canvas.width,height: canvas.height}bg.src = "../../image/白屏竖.png"bg.onload = () =>{ctx.drawImage(bg,0,0,canvas.width,canvas.height)}this.setData({canvas: canvas,ctx: ctx,bg_info: bg_info})})},

绘制矩形

可在whml添加按钮或图表，点击后调用绘制矩形函数，作为测试，也可在以上onReady函数获取画布对象后调用绘制矩形函数。

data:{edit_rect:{}
},
draw_basic_rect(){ctx.strokeRect(100,100,100,100)var t_edit = {left_top_x: 100,left_top_y: 100,width: 100,height: 100}this.setData({edit_rect: t_edit,current_edit_element: e.currentTarget.dataset.info})this.draw_rect_edit_icon() //绘