HTML5 Canvas Grayscale Image Filter Tutorial

To apply filter to an Konva.Image, we have to cache it first with cache() function. Then apply filter with filters() function.

To invert the colors of an image with Konva, we can use the Konva.Filters.Grayscale filter.

For all available filters go to Filters Documentation.

Vanilla

import Konva from 'konva';

const stage = new Konva.Stage({
  container: 'container',
  width: window.innerWidth,
  height: window.innerHeight,
});

const layer = new Konva.Layer();
stage.add(layer);

const imageObj = new Image();
imageObj.onload = () => {
  const image = new Konva.Image({
    x: 50,
    y: 50,
    image: imageObj,
    draggable: true,
  });

  layer.add(image);

  image.cache();
  image.filters([Konva.Filters.Grayscale]);
  layer.draw();
};
imageObj.src = 'https://new.konvajs.org/assets/lion.png';
imageObj.crossOrigin = 'anonymous';

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React

import { Stage, Layer, Image } from 'react-konva';
import { useState, useEffect, useRef } from 'react';
import useImage from 'use-image';

const App = () => {
  const [image] = useImage('https://new.konvajs.org/assets/lion.png', 'anonymous');
  const imageRef = useRef(null);

  useEffect(() => {
    if (image) {
      imageRef.current.cache();
    }
  }, [image]);

  return (
    <Stage width={window.innerWidth} height={window.innerHeight}>
      <Layer>
        {image && (
          <Image
            ref={imageRef}
            x={50}
            y={50}
            image={image}
            draggable
            filters={[Konva.Filters.Grayscale]}
          />
        )}
      </Layer>
    </Stage>
  );
};

export default App;

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Vue

<template>
  <v-stage :config="stageSize">
    <v-layer>
      <v-image
        ref="imageNode"
        :config="{
          x: 50,
          y: 50,
          image: image,
          draggable: true,
          filters: [Konva.Filters.Grayscale],
        }"
      />
    </v-layer>
  </v-stage>
</template>

<script setup>
import { ref, watch, nextTick } from 'vue';
import { useImage } from 'vue-konva';
import Konva from 'konva';

const stageSize = {
  width: window.innerWidth,
  height: window.innerHeight,
};

const imageNode = ref(null);
const [image] = useImage('https://new.konvajs.org/assets/lion.png', 'anonymous');

watch(image, async (newImage) => {
  if (newImage) {
    await nextTick();
    imageNode.value.getNode().cache();
  }
});
</script>

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