[英]drawImage not working on canvas
我正在使用chart.js庫,並且想繪制圖像。 我設置了一些CSS,以使畫布“響應”,但未顯示img。
CSS:
canvas{
width: 100% !important;
height: auto !important;
}
帆布:
<div class="col-lg-6">
<div class="content-panel">
<h4><i class="fa fa-angle-right"></i> Categories</h4>
<div class="panel-body text-center">
<canvas id="radar_best"></canvas>
</div>
</div>
</div>
JS:
base_image = new Image();
base_image.src = '../../images/no_data_graph.jpg';
console.log(base_image.src);
console.log("setting image");
document.getElementById("radar_best").getContext("2d").drawImage(base_image, 100,100);
img URL很好。 非常感謝。
加載圖像會花費一些時間,當您在當前代碼中執行drawImage
時,如果要使用它,則可能不會加載該圖像,這會導致意外結果。
您應該使用base_image.onload
,當圖像完全加載時將調用它。 然后,您可以使用drawImage
在畫布上繪制加載的圖像。
base_image = new Image();
base_image.onload = function() {
// When image loaded, you can then draw it on the canvas.
document.getElementById("radar_best").getContext("2d").drawImage(base_image, 100,100);
};
base_image.onerror = function() {
// It's always good to have some error handling.
console.log('image load error').
// do somthing else....
};
//always set the src after the onload callback as it is possible that image is already loaded in the browser memory hence onload event will never fire
base_image.src = '../../images/no_data_graph.jpg';
console.log(base_image.src);
console.log("setting image");
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