Code that outputs its own source to a canvas as grayscale values.

image_quine.js

(F=(L,d)=>{(C=d.createElement("canvas")).width=C.height=L;X=C.getContext("2d");for(i=L*L;i--;)X.fillStyle=`rgb(${n=`(F=${F})(16,document)`.charCodeAt(i)||32},${n},${n})`,X.fillRect(i%L,0|(i/L),1,1);d.body.appendChild(C)})(16,document)

// After running this code you should be able to grab the pixel values as a Uint8ClampedArray 
// from the canvas context 'X' and use that to verify like so:

var charCodes = Array.from(X.getImageData(0,0,16,16).data).filter((_,i)=>i%4===0)
String.fromCharCode.apply(null, charCodes)