Modifying an image without generating a fresh one

Question

Modifying an image without generating a fresh one

Has anyone figured out a way to modify an existing image (img element) using JavaScript without generating a new one? Most of the information I found online only talks about creating a new image with desired changes, but for performance reasons, I want to avoid that. Is there a way to achieve this in a browser environment?

I'm specifically looking to make real-time edits to a large uv map of a three.js model without constantly recreating the entire image due to performance concerns.

javascript image canvas three.js

Answer 1

Answer №1

Looking for a great image manipulation library? Check out p5.js

If you're wondering whether p5.js can directly alter an HTML-created img element, it might not be possible. However, loading images with JS is a viable alternative.

Check out this example that demonstrates how to adjust pixel brightness:


var img;

function preload() {
  img = loadImage("image.png");
}

function setup() {
  createCanvas(720, 200);
  img.loadPixels();
  loadPixels();
}

function draw() {
  for (var x = 0; x < img.width; x++) {
    for (var y = 0; y < img.height; y++) {
      var loc = (x + y*img.width)*4;
      var r, g, b;
      r = img.pixels[loc];
      var maxdist = 50;
      var d = dist(x, y, mouseX, mouseY);
      var adjustbrightness = 255 * (maxdist - d) / maxdist;
      r += adjustbrightness;
      r = constrain(r, 0, 255);
      
      var pixloc = (y*width + x)*4;
      pixels[pixloc] = r;
      pixels[pixloc+1] = r;
      pixels[pixloc+2] = r;
      pixels[pixloc+3] = 255;
    }
  }
  updatePixels();
}

Answer 2

Looking for a great image manipulation library? Check out p5.js

If you're wondering whether p5.js can directly alter an HTML-created img element, it might not be possible. However, loading images with JS is a viable alternative.

Check out this example that demonstrates how to adjust pixel brightness:


var img;

function preload() {
  img = loadImage("image.png");
}

function setup() {
  createCanvas(720, 200);
  img.loadPixels();
  loadPixels();
}

function draw() {
  for (var x = 0; x < img.width; x++) {
    for (var y = 0; y < img.height; y++) {
      var loc = (x + y*img.width)*4;
      var r, g, b;
      r = img.pixels[loc];
      var maxdist = 50;
      var d = dist(x, y, mouseX, mouseY);
      var adjustbrightness = 255 * (maxdist - d) / maxdist;
      r += adjustbrightness;
      r = constrain(r, 0, 255);
      
      var pixloc = (y*width + x)*4;
      pixels[pixloc] = r;
      pixels[pixloc+1] = r;
      pixels[pixloc+2] = r;
      pixels[pixloc+3] = 255;
    }
  }
  updatePixels();
}

Modifying an image without generating a fresh one

Answer №1

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