threejs/examples/jsm/effects/AsciiEffect.js

/**
 * Ascii generation is based on https://github.com/hassadee/jsascii/blob/master/jsascii.js
 *
 * 16 April 2012 - @blurspline
 */

class AsciiEffect {

	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 fResolution = options[ 'resolution' ] || 0.15; // Higher for more details
		const iScale = options[ 'scale' ] || 1;
		const bColor = options[ 'color' ] || false; // nice but slows down rendering!
		const bAlpha = options[ 'alpha' ] || false; // Transparency
		const bBlock = options[ 'block' ] || false; // blocked characters. like good O dos
		const bInvert = options[ 'invert' ] || false; // black is white, white is black
		const strResolution = options[ '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( oAscii );

		};

		this.domElement = domElement;


		// Throw in ascii library from https://github.com/hassadee/jsascii/blob/master/jsascii.js (MIT License)

		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;

		// 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( 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;

		}

	}

}

export { AsciiEffect };