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mrdoob/html2canvas.js

Created March 9, 2020 23:36
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  1. mrdoob created this gist Mar 9, 2020.
    189 changes: 189 additions & 0 deletions html2canvas.js
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,189 @@
    /**
    * @author mrdoob / http://mrdoob.com/
    */

    function html2canvas( element ) {

    var range = document.createRange();

    function Clipper( context ) {

    var clips = [];
    var isClipping = false;

    function doClip() {

    if ( isClipping ) {

    isClipping = false;
    context.restore();

    }

    if ( clips.length === 0 ) return;

    var minX = - Infinity, minY = - Infinity;
    var maxX = Infinity, maxY = Infinity;

    for ( var i = 0; i < clips.length; i ++ ) {

    var clip = clips[ i ];

    minX = Math.max( minX, clip.x );
    minY = Math.max( minY, clip.y );
    maxX = Math.min( maxX, clip.x + clip.width );
    maxY = Math.min( maxY, clip.y + clip.height );

    }

    context.save();
    context.beginPath();
    context.rect( minX, minY, maxX - minX, maxY - minY );
    context.clip();

    isClipping = true;

    }

    return {
    add: function ( clip ) {
    clips.push( clip );
    doClip();
    },
    remove: function () {
    clips.pop();
    doClip();
    }
    };

    }

    function drawText( style, x, y, string ) {

    if ( string !== '' ) {

    context.font = style.fontSize + ' ' + style.fontFamily;
    context.textBaseline = 'top';
    context.fillStyle = style.color;
    context.fillText( string, x, y );

    }

    }

    function drawBorder( style, which, x, y, width, height ) {

    var borderWidth = style[ which + 'Width' ];
    var borderStyle = style[ which + 'Style' ];
    var borderColor = style[ which + 'Color' ];

    if ( borderWidth !== '0px' && borderStyle !== 'none' && borderColor !== 'transparent' && borderColor !== 'rgba(0, 0, 0, 0)' ) {

    context.strokeStyle = borderColor;
    context.beginPath();
    context.moveTo( x, y );
    context.lineTo( x + width, y + height );
    context.stroke();

    }

    }

    function drawElement( element, style ) {

    var x = 0, y = 0, width = 0, height = 0;

    if ( element.nodeType === 3 ) {

    // text

    range.selectNode( element );

    var rect = range.getBoundingClientRect();

    x = rect.left - offset.left - 0.5;
    y = rect.top - offset.top - 0.5;
    width = rect.width;
    height = rect.height;

    drawText( style, x, y, element.nodeValue.trim() );

    } else {

    if ( element.style.display === 'none' ) return;

    var rect = element.getBoundingClientRect();

    x = rect.left - offset.left - 0.5;
    y = rect.top - offset.top - 0.5;
    width = rect.width;
    height = rect.height;

    style = window.getComputedStyle( element );

    var backgroundColor = style.backgroundColor;

    if ( backgroundColor !== 'transparent' && backgroundColor !== 'rgba(0, 0, 0, 0)' ) {

    context.fillStyle = backgroundColor;
    context.fillRect( x, y, width, height );

    }

    drawBorder( style, 'borderTop', x, y, width, 0 );
    drawBorder( style, 'borderLeft', x, y, 0, height );
    drawBorder( style, 'borderBottom', x, y + height, width, 0 );
    drawBorder( style, 'borderRight', x + width, y, 0, height );

    if ( element.type === 'color' || element.type === 'text' ) {

    clipper.add( { x: x, y: y, width: width, height: height } );

    drawText( style, x + parseInt( style.paddingLeft ), y + parseInt( style.paddingTop ), element.value );

    clipper.remove();

    }

    }

    /*
    // debug
    context.strokeStyle = '#' + Math.random().toString( 16 ).slice( - 3 );
    context.strokeRect( x - 0.5, y - 0.5, width + 1, height + 1 );
    */

    var isClipping = style.overflow === 'auto' || style.overflow === 'hidden';

    if ( isClipping ) clipper.add( { x: x, y: y, width: width, height: height } );

    for ( var i = 0; i < element.childNodes.length; i ++ ) {

    drawElement( element.childNodes[ i ], style );

    }

    if ( isClipping ) clipper.remove();

    }

    var offset = element.getBoundingClientRect();

    var canvas = document.createElement( 'canvas' );
    canvas.width = offset.width;
    canvas.height = offset.height;

    var context = canvas.getContext( '2d'/*, { alpha: false }*/ );

    var clipper = new Clipper( context );

    console.time( 'drawElement' );

    drawElement( element );

    console.timeEnd( 'drawElement' );

    return canvas;

    }