[英]Javascript Image not Drawing on Canvas after Drawing it to Offscreen Canvas
我有一个要渲染到画布的图像。 当我像这样渲染它时:
context.drawImage(image, x, y);
它按预期工作。 但是,当我这样做时:
if (image.loaded)
image = getPreRendered(image);
...
var renderedImages = [];
var tmpImage = null;
function getPreRendered(img) {
imageIndex = ("" + img.src);
tmpImage = cachedSprays[tmpIndex];
if (tmpImage == undefined) {
var tmpCanvas = document.createElement("canvas");
var tmpContext = tmpCanvas.getContext('2d');
tmpCanvas.width = 50;
tmpCanvas.height = 50;
tmpContext.drawImage(img, 0, 0, 100, 100);
tmpContext.imageSmoothingEnabled = false;
tmpContext.webkitImageSmoothingEnabled = false;
tmpContext.mozImageSmoothingEnabled = false;
tmpContext.drawImage(tmpCanvas, 0, 0, 50, 50, 0, 0, 100, 100);
tmpImage = tmpCanvas;
cachedSprays[imageIndex] = tmpImage ;
}
return tmpImage ;
}
但是,当我这样做时,图像在画布上不再可见。
图像是这样创建的:
var image = new Image();
image.loaded = false;
image.onload = function () {
image.loaded = true;
};
AJAX 和图像调用是异步的。 图像将/将加载,但您已经在图像仍在加载时调用了该函数。
var image = new Image();
image.onload = function () {
// call here your render canvas function:
getPreRendered( image );
};
image.src = "nOOdes.jpg"
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