constructor( renderer, charSet = ' .:-=+*#%@', options = {} ) {

			// ' .,:;=|iI+hHOE#`$';
			// darker bolder character set from https://github.com/saw/Canvas-ASCII-Art/
			// ' .\'`^",:;Il!i~+_-?][}{1)(|/tfjrxnuvczXYUJCLQ0OZmwqpdbkhao*#MW&8%B@$'.split('');
			// Some ASCII settings
			const bResolution = ! options[ 'resolution' ] ? 0.15 : options[ 'resolution' ]; // Higher for more details

			const iScale = ! options[ 'scale' ] ? 1 : options[ 'scale' ];
			const bColor = ! options[ 'color' ] ? false : options[ 'color' ]; // nice but slows down rendering!

			const bAlpha = ! options[ 'alpha' ] ? false : options[ 'alpha' ]; // Transparency

			const bBlock = ! options[ 'block' ] ? false : options[ 'block' ]; // blocked characters. like good O dos

			const bInvert = ! options[ 'invert' ] ? false : options[ 'invert' ]; // black is white, white is black

			const strResolution = 'low';
			let width, height;
			const domElement = document.createElement( 'div' );
			domElement.style.cursor = 'default';
			const oAscii = document.createElement( 'table' );
			domElement.appendChild( oAscii );
			let iWidth, iHeight;
			let oImg;

			this.setSize = function ( w, h ) {

				width = w;
				height = h;
				renderer.setSize( w, h );
				initAsciiSize();

			};

			this.render = function ( scene, camera ) {

				renderer.render( scene, camera );
				asciifyImage( renderer, oAscii );

			};

			this.domElement = domElement; // Throw in ascii library from http://www.nihilogic.dk/labs/jsascii/jsascii.js

			/*
    * jsAscii 0.1
    * Copyright (c) 2008 Jacob Seidelin, jseidelin@nihilogic.dk, http://blog.nihilogic.dk/
    * MIT License [http://www.nihilogic.dk/licenses/mit-license.txt]
    */

			function initAsciiSize() {

				iWidth = Math.round( width * fResolution );
				iHeight = Math.round( height * fResolution );
				oCanvas.width = iWidth;
				oCanvas.height = iHeight; // oCanvas.style.display = "none";
				// oCanvas.style.width = iWidth;
				// oCanvas.style.height = iHeight;

				oImg = renderer.domElement;

				if ( oImg.style.backgroundColor ) {

					oAscii.rows[ 0 ].cells[ 0 ].style.backgroundColor = oImg.style.backgroundColor;
					oAscii.rows[ 0 ].cells[ 0 ].style.color = oImg.style.color;

				}

				oAscii.cellSpacing = 0;
				oAscii.cellPadding = 0;
				const oStyle = oAscii.style;
				oStyle.display = 'inline';
				oStyle.width = Math.round( iWidth / fResolution * iScale ) + 'px';
				oStyle.height = Math.round( iHeight / fResolution * iScale ) + 'px';
				oStyle.whiteSpace = 'pre';
				oStyle.margin = '0px';
				oStyle.padding = '0px';
				oStyle.letterSpacing = fLetterSpacing + 'px';
				oStyle.fontFamily = strFont;
				oStyle.fontSize = fFontSize + 'px';
				oStyle.lineHeight = fLineHeight + 'px';
				oStyle.textAlign = 'left';
				oStyle.textDecoration = 'none';

			}

			const aDefaultCharList = ' .,:;i1tfLCG08@'.split( '' );
			const aDefaultColorCharList = ' CGO08@'.split( '' );
			const strFont = 'courier new, monospace';
			const oCanvasImg = renderer.domElement;
			const oCanvas = document.createElement( 'canvas' );

			if ( ! oCanvas.getContext ) {

				return;

			}

			const oCtx = oCanvas.getContext( '2d' );

			if ( ! oCtx.getImageData ) {

				return;

			}

			let aCharList = bColor ? aDefaultColorCharList : aDefaultCharList;
			if ( charSet ) aCharList = charSet;
			let fResolution = 0.5;

			switch ( strResolution ) {

				case 'low':
					fResolution = 0.25;
					break;

				case 'medium':
					fResolution = 0.5;
					break;

				case 'high':
					fResolution = 1;
					break;

			}

			if ( bResolution ) fResolution = bResolution; // Setup dom

			const fFontSize = 2 / fResolution * iScale;
			const fLineHeight = 2 / fResolution * iScale; // adjust letter-spacing for all combinations of scale and resolution to get it to fit the image width.

			let fLetterSpacing = 0;

			if ( strResolution == 'low' ) {

				switch ( iScale ) {

					case 1:
						fLetterSpacing = - 1;
						break;

					case 2:
					case 3:
						fLetterSpacing = - 2.1;
						break;

					case 4:
						fLetterSpacing = - 3.1;
						break;

					case 5:
						fLetterSpacing = - 4.15;
						break;

				}

			}

			if ( strResolution == 'medium' ) {

				switch ( iScale ) {

					case 1:
						fLetterSpacing = 0;
						break;

					case 2:
						fLetterSpacing = - 1;
						break;

					case 3:
						fLetterSpacing = - 1.04;
						break;

					case 4:
					case 5:
						fLetterSpacing = - 2.1;
						break;

				}

			}

			if ( strResolution == 'high' ) {

				switch ( iScale ) {

					case 1:
					case 2:
						fLetterSpacing = 0;
						break;

					case 3:
					case 4:
					case 5:
						fLetterSpacing = - 1;
						break;

				}

			} // can't get a span or div to flow like an img element, but a table works?
			// convert img element to ascii


			function asciifyImage( canvasRenderer, oAscii ) {

				oCtx.clearRect( 0, 0, iWidth, iHeight );
				oCtx.drawImage( oCanvasImg, 0, 0, iWidth, iHeight );
				const oImgData = oCtx.getImageData( 0, 0, iWidth, iHeight ).data; // Coloring loop starts now

				let strChars = ''; // console.time('rendering');

				for ( let y = 0; y < iHeight; y += 2 ) {

					for ( let x = 0; x < iWidth; x ++ ) {

						const iOffset = ( y * iWidth + x ) * 4;
						const iRed = oImgData[ iOffset ];
						const iGreen = oImgData[ iOffset + 1 ];
						const iBlue = oImgData[ iOffset + 2 ];
						const iAlpha = oImgData[ iOffset + 3 ];
						let iCharIdx;
						let fBrightness;
						fBrightness = ( 0.3 * iRed + 0.59 * iGreen + 0.11 * iBlue ) / 255; // fBrightness = (0.3*iRed + 0.5*iGreen + 0.3*iBlue) / 255;

						if ( iAlpha == 0 ) {

							// should calculate alpha instead, but quick hack :)
							//fBrightness *= (iAlpha / 255);
							fBrightness = 1;

						}

						iCharIdx = Math.floor( ( 1 - fBrightness ) * ( aCharList.length - 1 ) );

						if ( bInvert ) {

							iCharIdx = aCharList.length - iCharIdx - 1;

						} // good for debugging
						//fBrightness = Math.floor(fBrightness * 10);
						//strThisChar = fBrightness;


						let strThisChar = aCharList[ iCharIdx ];
						if ( strThisChar === undefined || strThisChar == ' ' ) strThisChar = '&nbsp;';

						if ( bColor ) {

							strChars += '<span style=\'' + 'color:rgb(' + iRed + ',' + iGreen + ',' + iBlue + ');' + ( bBlock ? 'background-color:rgb(' + iRed + ',' + iGreen + ',' + iBlue + ');' : '' ) + ( bAlpha ? 'opacity:' + iAlpha / 255 + ';' : '' ) + '\'>' + strThisChar + '</span>';

						} else {

							strChars += strThisChar;

						}

					}

					strChars += '<br/>';

				}

				oAscii.innerHTML = '<tr><td>' + strChars + '</td></tr>'; // console.timeEnd('rendering');
				// return oAscii;

			}

		}
Ascii generation is based on http://www.nihilogic.dk/labs/jsascii/
Maybe more about this later with a blog post at http://lab4games.net/zz85/blog

16 April 2012 - @blurspline