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

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Sometimes, we want to check if a specific pixel of an image is transparent with JavaScript.

In this article, we’ll look at how to check if a specific pixel of an image is transparent with JavaScript.

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 put the image in the canvas.

Then we can get the pixel’s data from there.

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 img element with getElementById.

Then we create a canvas with createElement.

Then we set its width and height.

Next, we get its context with getContext.

Then we call drawImage to draw the img image onto the canvas.

Finally, we get the pixel data with getImageData.

Conclusion

To check if a specific pixel of an image is transparent with JavaScript, we put the image in the canvas.

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