Canvas 在 firefox 上绘制图像问题，在 chrome 中运行良好

Question

我认为这是某种兼容性问题。在 chrome 中一切正常，但在 firefox 中 <canvas> 根本不绘制任何东西。

function drawStage(stageNum) {
    var cap = canvasArray.length; //keeps the canvasElements
    var i;
    var stageImages = images["stage" + stageNum];
    var stageDimensions = imageDimensions["stage" + stageNum];
    //console.log("Cap is: " + cap);


    for (i = 0; i < cap; i++) {
        var canvas = document.getElementById(canvasArray[i]);
        var canvasContext = canvas.getContext("2d");
        var image = document.getElementById(stageImages[i]);

        canvasContext.clearRect(0, 0, 1280, 1280);
        canvasContext.drawImage(image, stageDimensions[i][0], stageDimensions[i][1], stageDimensions[i][2], stageDimensions[i][3]);
        //document.getElementById(zIndexes[i][0]).style["z-index"] = zIndexes[i][stageNum];
        //console.log(document.getElementById(zIndexes[i][0]).id);
    }
}

编辑： here 是我制作的 "test" 代码示例的保管箱 link，更简单，1 张图像，1 canvas, 1 div, 类似（几乎相同）的脚本，在 firefox 中仍然不能工作，但在 chrome 中工作。如果你能解决那里的问题，那么这个问题也就解决了。

更新： 数组如下，根据请求，它们是不同 elements/coordinates 的简单输入。不过我向你保证，数组本身没有问题，在 chrome 中一切正常。函数中的 DrawImage() 方法导致了我要说的问题。（数组下方有进一步解释）

images 是 <img> 元素的（全局）id 数组。

    var images = {
    stage1: ["character1Base", "character2Base", "character3Base", "character4Base", "character5Base", "character6Base", "character3BotImg"],
    stage2: ["character1Sit", "character2Base", "character3Base", "character4Base", "character5Base", "character6Base", "character3BotImg"],
    stage3: ["character1Sit", "character2Drink", "character3Base", "character4Base", "character5Base", "character6Base", "character3BotImg"],
    stage4: ["character1Sit", "character2Drink", "character3Base", "character4Base", "character5Base", "character6Doll", "character3BotImg"],
    stage5: ["character1Sit", "character2Drink", "character3Eat", "character4Base", "character5Base", "character6Doll", "character3EatBot"],
    stage6: ["character1Sit", "character2Stand", "character3Eat", "character4Base", "character5Base", "character6Doll", "character3EatBot"],
    stage7: ["character1Sit", "character2Stand", "character3Eat", "character4Sit", "character5Base", "character6Doll", "character3EatBot"],
    stage8: ["character1Sit", "character2Stand", "character3Eat", "character4Sit", "character5Sit", "character6Doll", "character3EatBot"],
    stage9: ["character1Sit", "character2Eat", "character3Eat", "character4Sit", "character5Sit", "character6Doll", "character3EatBot"],
    stage10: ["character1Drink", "character2Eat", "character3Eat", "character4Sit", "character5Sit", "character6Doll", "character3EatBot"]
};

imageDimensions 是 well、dimensions、posX、posY、sizeX 和 sizeY 的（全局）数组。

    var imageDimensions = {
    stage1: [[0, 0, 233, 485], [0, 0, 153, 407], [20, 0, 220, 200], [0, 150, 505, 210], [0, 0, 315, 391], [0, 0, 480, 435], [1, 0, 220, 180]],
    stage2: [[105, 35, 180, 440], [0, 0, 153, 407], [20, 0, 220, 200], [0, 150, 505, 210], [0, 0, 315, 391], [0, 0, 480, 435], [1, 0, 220, 180]],
    stage3: [[105, 35, 180, 440], [0, 0, 153, 407], [20, 0, 220, 200], [0, 150, 505, 210], [0, 0, 315, 391], [0, 0, 480, 435], [1, 0, 220, 180]],
    stage4: [[105, 35, 180, 440], [0, 0, 153, 407], [20, 0, 220, 200], [0, 150, 505, 210], [0, 0, 315, 391], [0, 0, 480, 435], [1, 0, 220, 180]],
    stage5: [[105, 35, 180, 440], [0, 0, 153, 407], [3, 7, 226, 180], [0, 150, 505, 210], [0, 0, 315, 391], [0, 0, 480, 435], [1, 9, 220, 180]],
    stage6: [[105, 35, 180, 440], [0, 0, 172, 490], [3, 7, 226, 180], [0, 150, 505, 210], [0, 0, 315, 391], [0, 0, 480, 435], [1, 9, 220, 180]],
    stage7: [[105, 35, 180, 440], [0, 0, 172, 490], [3, 7, 226, 180], [70, 0, 341, 380], [0, 0, 315, 391], [0, 0, 480, 435], [1, 9, 220, 180]],
    stage8: [[105, 35, 180, 440], [0, 0, 172, 490], [3, 7, 226, 180], [70, 0, 341, 380], [18, 72, 305, 422], [0, 0, 480, 435], [1, 9, 220, 180]],
    stage9: [[105, 35, 180, 440], [0, 0, 173, 473], [3, 7, 226, 180], [70, 0, 341, 380], [18, 72, 305, 422], [0, 0, 480, 435], [1, 9, 220, 180]],
    stage10: [[105, 32, 162, 440], [0, 0, 173, 473], [3, 7, 226, 180], [70, 0, 341, 380], [18, 72, 305, 422], [0, 0, 480, 435], [1, 9, 220, 180]]
};

解释： 该功能旨在以不同的元素在屏幕上绘制，属于这些元素的字符。它们绘制于 canvas （稍后也会在 canvas 中进行动画处理）。 stageNum 即该函数采用的唯一参数决定了将绘制什么。

有人知道问题出在哪里吗？（我读过一些类似的帖子，但所有问题都是鼠标位置的 layerX、layerY，但是我在这里根本没有使用 mouseover / mousein / mouseout，仍然没有绘制元素。

Answer 1

您的问题是您尝试绘制的图像是 svg 图像，并且这些 svg 文档具有相对的 width 和 height 属性。

浏览器无法为其必须绘制的图像设置高度或宽度，因此无法将其呈现给 canvas。（它能够在文档中进行估计，因为它可以与某物相关，但不能在 canvas 中）。

因此解决方案是在您的 svg 文件中设置绝对 width 和 height 属性，

或者更复杂，首先将其绘制成 <iframe> 或 <object>，然后绘制一个序列化版本，您将在其中设置这些属性。

function initialize() {
    var canvas = document.getElementById("char1Canvas");
    var canvasContext = canvas.getContext("2d");
    var image = document.getElementById("char1Img");
    resizeSVG(image, function(e){
        canvasContext.clearRect(0, 0, 1280, 1280);
        canvasContext.drawImage(this, 0, 0);
    });
};

var resizeSVG = function(svgImg, callback){
    // create an iframe
    var iframe = document.createElement('iframe');
    // so we don't see it
    iframe.height = 0;
    iframe.width = 0;
    iframe.onload = function(){
        var doc = iframe.contentDocument;
        var svg = doc.querySelector('svg');
        // get the computed width and height of your img element
        // should probably be tweaked
        var bbox = svgImg.getBoundingClientRect();
        // if it's a relative width
        if (svg.width.baseVal.unitType !== 1) {
            svg.setAttribute('width', bbox.width);
        }
        // or a relative height
        if (svg.height.baseVal.unitType !== 1) {
            svg.setAttribute('height', bbox.height);
        }
        // serialize our updated svg
        var svgData = (new XMLSerializer()).serializeToString(svg);
        var svgURL = 'data:image/svg+xml; charset=utf8, ' + encodeURIComponent(svgData);
        // create a new Image Object that ill be draw on the canvas
        var img = new Image();
        img.onload = callback;
        img.src = svgURL;
        // remove the iframe
        document.body.removeChild(iframe);
    };
    iframe.src = svgImg.src;
    document.body.appendChild(iframe);
}

Canvas 在 firefox 上绘制图像问题，在 chrome 中运行良好

Canvas Draw Image issue on firefox, works well in chrome

javascript

firefox

canvas

drawimage