let c = document.getElementById(canvas) let canvas = document.createElement(canvas) let availHeight = document.documentElement.clientHeight let off = availHeight - 400 canvas.height = '350' canvas.width = c.clientWidth c.appendChild(canvas) let dr = canvas.getContext('2d') dr.strokeStyle = 'blue' canvas.addEventListener('touchstart',(e)=>{ dr.beginPath() dr.moveto(e.changedtouches[0].pageX,e.changedtouches[0].pageY-off) }) canvas.addEventListener('touchmove',(e)=>{ dr.lineto(e.changedtouches[0].pageX, e.changedtouches[0].pageY-off) dr.stroke() }) canvas.addEventListener('touchend',(e)=>{ dr.closePath() })
let img = document.querySelector('canvas').toDataURL()
如需发送给后端,可以让后端支持base64或者blob、buffer
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