所属分类：web前端开发
在本教程中，我们将学习如何使用 FabricJS 获取图像的不透明度。我们可以通过创建fabric.Image的实例来创建一个Image对象。由于它是 FabricJS 的基本元素之一，我们还可以通过应用角度、不透明度等属性轻松自定义它。为了获取 Image 的不透明度，我们使用 getObjectOpacity 方法。 p>
getObjectOpacity(): Number
让我们看一个代码示例，以查看使用 getObjectOpacity 方法时记录的输出。在这种情况下，控制台中将显示默认的不透明度，即 1。
微博登录
QQ登录<!DOCTYPE html>
<html>
<head>
<!-- Adding the Fabric JS Library-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script>
</head>
<body>
<h2>Using the getObjectOpacity method</h2>
<p>
You can open console from dev tools and see that the logged value is
being displayed in the console
</p>
<canvas id="canvas"></canvas>
<img src="https://img.zzsucai.com/202308/30/4BPvc624847084132.png" id="img1" style="display: none" />
<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
// Initiating the image element
var imageElement = document.getElementById("img1");
// Initiate an Image object
var image = new fabric.Image(imageElement, {
top: 50,
left: 110,
});
// Add it to the canvas
canvas.add(image);
// Using getObjectOpacity method
console.log("The opacity is: ", image.getObjectOpacity());
</script>
</body>
</html>
让我们看一个代码示例，以查看当 getObjectOpacity 方法与 opacity 属性结合使用时记录的输出。在本例中，图像对象的不透明度被指定为 0.7，因此记录的输出将为 0.7。
<!DOCTYPE html>
<html>
<head>
<!-- Adding the Fabric JS Library-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script>
</head>
<body>
<h2>Using the getObjectOpacity method and passing the opacity property</h2>
<p>
You can open console from dev tools and see that the opacity value is being displayed in the console
</p>
<canvas id="canvas"></canvas>
<img src="https://img.zzsucai.com/202308/30/4BPvc624847084132.png" id="img1" style="display: none" />
<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
// Initiating the image element
var imageElement = document.getElementById("img1");
// Initiate an Image object
var image = new fabric.Image(imageElement, {
top: 50,
left: 110,
opacity: 0.7,
});
// Add it to the canvas
canvas.add(image);
// Using getObjectOpacity method
console.log("The opacity is: ", image.getObjectOpacity());
</script>
</body>
</html>
