给图片添加滤镜前，我们必须先使用cache()方法将它缓存起来，然后使用filter()方法添加滤镜。
我们可以使用Konva.Filters.Grayscale滤镜去掉图片颜色。
查看所有滤镜 Filters Documentation.
Konva Grayscale Image Demoview raw<!DOCTYPE html>
<html>
<head>
<script src="https://unpkg.com/konva@4.0.18/konva.min.js"></script>
<meta charset="utf-8" />
<title>Konva Grayscale Image Demo</title>
<style>
body {
margin: 0;
padding: 0;
overflow: hidden;
background-color: #f0f0f0;
}
</style>
</head>
<body>
<div id="container"></div>
<script>
function loadImages(sources, callback) {
var images = {};
var loadedImages = 0;
var numImages = 0;
for (var src in sources) {
numImages++;
}
for (var src in sources) {
images[src] = new Image();
images[src].onload = function() {
if (++loadedImages >= numImages) {
callback(images);
}
};
images[src].src = sources[src];
}
}
function buildStage(images) {
var stage = new Konva.Stage({
container: 'container',
width: window.innerWidth,
height: window.innerHeight
});
var layer = new Konva.Layer();
var lion = new Konva.Image({
image: images.lion,
x: 80,
y: 30,
draggable: true
});
lion.cache();
lion.filters([Konva.Filters.Grayscale]);
layer.add(lion);
stage.add(layer);
}
var sources = {
lion: '/assets/lion.png'
};
loadImages(sources, buildStage);
</script>
</body>
</html>
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