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isCanvasBlocked.js
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isCanvasBlocked.js
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//
// Canvas Blocker &
// Firefox privacy.resistFingerprinting Detector.
// (c) 2018 // JOHN OZBAY // CRYPT.EE
// MIT License
//
function isCanvasBlocked () {
// create a 1px image data
var blocked = false;
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
// some blockers just return an undefined ctx. So let's check that first.
if (ctx) {
var imageData = ctx.createImageData(1,1);
var originalImageData = imageData.data;
// set pixels to RGB 128
originalImageData[0]=128;
originalImageData[1]=128;
originalImageData[2]=128;
originalImageData[3]=255;
// set this to canvas
ctx.putImageData(imageData,1,1);
try {
// now get the data back from canvas.
var checkData = ctx.getImageData(1, 1, 1, 1).data;
// If this is firefox, and privacy.resistFingerprinting is enabled,
// OR a browser extension blocking the canvas,
// This will return RGB all white (255,255,255) instead of the (128,128,128) we put.
// so let's check the R and G to see if they're 255 or 128 (matching what we've initially set)
if (originalImageData[0] !== checkData[0] && originalImageData[1] !== checkData[1]) {
blocked = true;
console.log("Canvas is blocked. Will display warning.");
}
} catch (error) {
// some extensions will return getImageData null. this is to account for that.
blocked = true;
console.log("Canvas is blocked. Will display warning.");
}
} else {
blocked = true;
console.log("Canvas is blocked. Will display warning.");
}
return blocked;
}