HTML5 Canvas RGB filter Image Tutorial

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

To change rgb components of an image with Konva, we can use the Konva.Filters.RGB.

Instructions: Slide the controls to change RGB values.

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.RGB]);
  image.red(100);
  image.green(100);
  image.blue(100);

  // create sliders
  const createSlider = (label, property) => {
    const container = document.createElement('div');
    container.style.position = 'absolute';
    container.style.left = '20px';
    
    const text = document.createElement('span');
    text.textContent = `${label}: `;
    container.appendChild(text);
    
    const slider = document.createElement('input');
    slider.type = 'range';
    slider.min = '0';
    slider.max = '255';
    slider.step = '1';
    slider.value = image[property]();
    slider.style.width = '200px';
    
    slider.addEventListener('input', (e) => {
      const value = parseInt(e.target.value);
      image[property](value);
    });
    
    container.appendChild(slider);
    return container;
  };

  const redSlider = createSlider('Red', 'red');
  redSlider.style.top = '20px';
  document.body.appendChild(redSlider);

  const greenSlider = createSlider('Green', 'green');
  greenSlider.style.top = '45px';
  document.body.appendChild(greenSlider);

  const blueSlider = createSlider('Blue', 'blue');
  blueSlider.style.top = '70px';
  document.body.appendChild(blueSlider);
};
imageObj.src = 'https://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 [red, setRed] = useState(100);
  const [green, setGreen] = useState(100);
  const [blue, setBlue] = useState(100);
  const [image] = useImage('https://konvajs.org/assets/lion.png', 'anonymous');
  const imageRef = useRef(null);

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

  return (
    <>
      <Stage width={window.innerWidth} height={window.innerHeight}>
        <Layer>
          <Image
            ref={imageRef}
            x={50}
            y={50}
            image={image}
            draggable
            filters={[Konva.Filters.RGB]}
            red={red}
            green={green}
            blue={blue}
          />
        </Layer>
      </Stage>
      <div style={{ position: 'absolute', top: '20px', left: '20px' }}>
        <div>
          Red
          <input
            type="range"
            min="0"
            max="255"
            value={red}
            onChange={(e) => setRed(parseInt(e.target.value))}
          />
        </div>
        <div>
          Green
          <input
            type="range"
            min="0"
            max="255"
            value={green}
            onChange={(e) => setGreen(parseInt(e.target.value))}
          />
        </div>
        <div>
          Blue
          <input
            type="range"
            min="0"
            max="255"
            value={blue}
            onChange={(e) => setBlue(parseInt(e.target.value))}
          />
        </div>
      </div>
    </>
  );
};

export default App;

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Vue

<template>
  <div>
    <v-stage :config="stageSize">
      <v-layer>
        <v-image
          ref="imageNode"
          :config="{
            x: 50,
            y: 50,
            image: image,
            draggable: true,
            filters: [Konva.Filters.RGB],
            red: red,
            green: green,
            blue: blue,
          }"
        />
      </v-layer>
    </v-stage>
    <div style="position: absolute; top: 20px; left: 20px">
      <div>
        Red
        <input
          type="range"
          min="0"
          max="255"
          :value="red"
          @input="(e) => red = parseInt(e.target.value)"
        />
      </div>
      <div>
        Green
        <input
          type="range"
          min="0"
          max="255"
          :value="green"
          @input="(e) => green = parseInt(e.target.value)"
        />
      </div>
      <div>
        Blue
        <input
          type="range"
          min="0"
          max="255"
          :value="blue"
          @input="(e) => blue = parseInt(e.target.value)"
        />
      </div>
    </div>
  </div>
</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 red = ref(100);
const green = ref(100);
const blue = ref(100);
const imageNode = ref(null);
const [image] = useImage('https://konvajs.org/assets/lion.png', 'anonymous');

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

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