How to check if a specific pixel of an image is transparent with JavaScript?

To check if a specific pixel of an image is transparent with JavaScript, we use the getImageData method.

For instance, we write

const img = document.getElementById("my-image");
const canvas = document.createElement("canvas");
canvas.width = img.width;
canvas.height = img.height;
canvas.getContext("2d").drawImage(img, 0, 0, img.width, img.height);

const pixelData = canvas
  .getContext("2d")
  .getImageData(event.offsetX, event.offsetY, 1, 1).data;

to select the image with getElementById.

and then we create a canvas with createElement

Next, we call drawImage to draw the img element image into the canvas.

And we get the image data at the pixel at event.offsetX, event.offsetY with getImageData by calling it with 1 and 1.