HTML5 Canvas Brighten 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 brighten or darken an image with Konva, we can use the Konva.Filters.Brighten filter and set the brightness amount with the brightness property. The brightness property can be set to any integer between -1 and 1. Negative values darken the image, and positive values brighten the image.

Instructions: Slide the control to adjust the brightness

For all available filters go to Filters Documentation.

Vanilla

import Konva from 'konva';

const width = window.innerWidth;
const height = window.innerHeight;

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

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.Brighten]);
  image.brightness(0.3);

  const slider = document.createElement('input');
  slider.type = 'range';
  slider.min = '-1';
  slider.max = '1';
  slider.step = '0.1';
  slider.value = image.brightness();

  slider.style.position = 'absolute';
  slider.style.top = '20px';
  slider.style.left = '20px';

  slider.addEventListener('input', (e) => {
    const value = parseFloat(e.target.value);
    image.brightness(value);
    layer.batchDraw();
  });

  document.body.appendChild(slider);
};

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 [brightness, setBrightness] = useState(0.3);
  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
            ref={imageRef}
            x={50}
            y={50}
            image={image}
            draggable
            filters={[Konva.Filters.Brighten]}
            brightness={brightness}
          />
        </Layer>
      </Stage>
      <input
        type="range"
        min="-1"
        max="1"
        step="0.1"
        value={brightness}
        onChange={(e) => setBrightness(parseFloat(e.target.value))}
        style={{ position: 'absolute', top: '20px', left: '20px' }}
      />
    </>
  );
};

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.Brighten],
            brightness: brightness,
          }"
        />
      </v-layer>
    </v-stage>
    <input
      type="range"
      min="-1"
      max="1"
      step="0.1"
      :value="brightness"
      @input="handleSlider"
      style="position: absolute; top: 20px; left: 20px"
    />
  </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 brightness = ref(0.3);
const imageNode = ref(null);
const [image] = useImage('https://new.konvajs.org/assets/lion.png', 'anonymous');

watch(image, async (newImage) => {
  if (newImage) {
    // wait for the next DOM update
    await nextTick();
    // now the image component is fully updated
    imageNode.value.getNode().cache();
  }
});

const handleSlider = (e) => {
  brightness.value = parseFloat(e.target.value);
};
</script>

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