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How Can I Get Base64-Encoded Image Data from Already Loaded Images in JavaScript?
How Can I Get Base64-Encoded Image Data from Already Loaded Images in JavaScript?
Dec 15, 2024 pm 10:56 PM
Extracting Image Data URLs in JavaScript
Problem:
How can you obtain base64-encoded content from images already loaded in a browser using HTML tags, without the need for re-downloading?
Solution for Greasemonkey and Firefox:
To extract the content of fully loaded images using Greasemonkey and Firefox, implement the following steps:
- Create a Canvas: Generate a canvas element with dimensions matching the image's size.
- Copy Image Data: Utilize the drawImage function to transfer the image's data to the canvas.
- Obtain Data URL: Employ the toDataURL function to retrieve the base64-encoded image data from the canvas.
function getBase64Image(img) {
var canvas = document.createElement("canvas");
canvas.width = img.width;
canvas.height = img.height;
var ctx = canvas.getContext("2d");
ctx.drawImage(img, 0, 0);
var dataURL = canvas.toDataURL("image/png");
return dataURL.replace(/^data:image\/(png|jpg);base64,/, "");
}
Note: This solution assumes image data is available from the same domain as the page or has the crossOrigin="anonymous" attribute enabled with server support for CORS. Additionally, the returned image may be re-encoded.
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