我會推薦使用多個畫布。
Live Demo
所以基本上他們做頂部一個繼續清除預拉伸,而一旦鬆開鼠標按鈕,它然後它繪製到較低的「永久」畫布。
來自小提琴的代碼,因爲jsFiddle最近一直很慢,所以想要將它加入以供參考。
var canvas = document.getElementById("canvas"),
ctx = canvas.getContext("2d"),
drawCanvas = document.getElementById("drawCanvas"),
drawCtx = drawCanvas.getContext("2d"),
painting = false,
lastX = 0,
lastY = 0,
curX = 0,
curY = 0,
startX = 0,
startY = 0,
lineThickness = 1;
canvas.width = canvas.height = 600;
drawCanvas.width = drawCanvas.height = 600;
drawCanvas.onmousedown = function(e) {
startX = e.pageX - this.offsetLeft;
startY = e.pageY - this.offsetTop;
painting = true;
};
drawCanvas.onmouseup = function(e){
painting = false;
ctx.strokeStyle = "#000";
ctx.beginPath();
ctx.moveTo(startX, startY);
ctx.lineTo(lastX, lastY);
ctx.stroke();
drawCtx.clearRect(0, 0, 600, 600);
}
drawCanvas.onmouseclick = function(e) {
startX = e.pageX - this.offsetLeft;
startY = e.pageY - this.offsetTop;
painting = true;
};
drawCanvas.onmousemove = function(e) {
if(painting){
lastX = e.pageX - this.offsetLeft;
lastY = e.pageY - this.offsetTop;
drawCtx.clearRect(0,0,600,600);
drawCtx.beginPath();
drawCtx.moveTo(startX ,startY);
drawCtx.lineTo(lastX, lastY);
drawCtx.stroke();
}
}