Canvas 转为图片

我们可以使用 Canvas2image 库将 canvas 转换为图片。

本地下载：http://static.runoob.com/assets/canvas2image/canvas2image.js。

Github 地址：https://github.com/hongru/canvas2image

使用方式如下：

Canvas2Image.saveAsImage(canvasObj, width, height, type)
Canvas2Image.saveAsPNG(canvasObj, width, height)
Canvas2Image.saveAsJPEG(canvasObj, width, height)
Canvas2Image.saveAsGIF(canvasObj, width, height)
Canvas2Image.saveAsBMP(canvasObj, width, height)

Canvas2Image.convertToImage(canvasObj, width, height, type)
Canvas2Image.convertToPNG(canvasObj, width, height)
Canvas2Image.convertToJPEG(canvasObj, width, height)
Canvas2Image.convertToGIF(canvasObj, width, height)
Canvas2Image.convertToBMP(canvasObj, width, height)

测试实例：

var canvas, ctx, bMouseIsDown = false, iLastX, iLastY,
$save, $imgs,
$convert, $imgW, $imgH,
$sel;
function init () {
    canvas = document.getElementById('cvs');
    ctx = canvas.getContext('2d');
    $save = document.getElementById('save');
    $convert = document.getElementById('convert');
    $sel = document.getElementById('sel');
    $imgs = document.getElementById('imgs');
    $imgW = document.getElementById('imgW');
    $imgH = document.getElementById('imgH');
    bind();
    draw();
}
function bind () {
    canvas.onmousedown = function(e) {
        bMouseIsDown = true;
        iLastX = e.clientX - canvas.offsetLeft + (window.pageXOffset||document.body.scrollLeft||document.documentElement.scrollLeft);
        iLastY = e.clientY - canvas.offsetTop + (window.pageYOffset||document.body.scrollTop||document.documentElement.scrollTop);
    }
    canvas.onmouseup = function() {
        bMouseIsDown = false;
        iLastX = -1;
        iLastY = -1;
    }
    canvas.onmousemove = function(e) {
        if (bMouseIsDown) {
            var iX = e.clientX - canvas.offsetLeft + (window.pageXOffset||document.body.scrollLeft||document.documentElement.scrollLeft);
            var iY = e.clientY - canvas.offsetTop + (window.pageYOffset||document.body.scrollTop||document.documentElement.scrollTop);
            ctx.moveTo(iLastX, iLastY);
            ctx.lineTo(iX, iY);
            ctx.stroke();
            iLastX = iX;
            iLastY = iY;
        }
    };
    
    $save.onclick = function (e) {
        var type = $sel.value,
            w = $imgW.value,
            h = $imgH.value;
        Canvas2Image.saveAsImage(canvas, w, h, type);
    }
    $convert.onclick = function (e) {
        var type = $sel.value,
            w = $imgW.value,
            h = $imgH.value;
        $imgs.appendChild(Canvas2Image.convertToImage(canvas, w, h, type))
    }
    
}
function draw () {
    ctx.fillStyle = '#ffffff';
    ctx.fillRect(0, 0, 600, 400);
    ctx.fillStyle = 'red';
    ctx.fillRect(100, 100, 50, 50);
}

尝试一下 »