I'm trying to change all black colors of my image into transparency in jimp js

I've done a lot of research on the subject and so far nothing, so I decided to come here and ask this question

CodePudding user response：

There is a snippet in github's issue, I've changed some parts for your case:

import Jimp from 'jimp';

Jimp.read('./sample.png').then(image => {
  const targetColor = {r: 0, g: 0, b: 0, a: 255};  // black
  const replaceColor = {r: 0, g: 0, b: 0, a: 0};  // transparent
  const colorDistance = (c1, c2) => Math.sqrt(Math.pow(c1.r - c2.r, 2)   Math.pow(c1.g - c2.g, 2)   Math.pow(c1.b - c2.b, 2)   Math.pow(c1.a - c2.a, 2));  // Distance between two colors
  const threshold = 32;
  image.scan(0, 0, image.bitmap.width, image.bitmap.height, (x, y, idx) => {
    const thisColor = {
      r: image.bitmap.data[idx   0],
      g: image.bitmap.data[idx   1],
      b: image.bitmap.data[idx   2],
      a: image.bitmap.data[idx   3]
    };
    if(colorDistance(targetColor, thisColor) <= threshold) {
      image.bitmap.data[idx   0] = replaceColor.r;
      image.bitmap.data[idx   1] = replaceColor.g;
      image.bitmap.data[idx   2] = replaceColor.b;
      image.bitmap.data[idx   3] = replaceColor.a;
    }
  });
  image.write('transparent.png');
});