pdfjs-dist/src/core/pattern.js

/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
/* Copyright 2012 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/* globals ColorSpace, PDFFunction, Util, error, warn, info, isArray, isStream,
           isPDFFunction, UnsupportedManager, UNSUPPORTED_FEATURES */

'use strict';

var PatternType = {
  AXIAL: 2,
  RADIAL: 3
};

var Pattern = (function PatternClosure() {
  // Constructor should define this.getPattern
  function Pattern() {
    error('should not call Pattern constructor');
  }

  Pattern.prototype = {
    // Input: current Canvas context
    // Output: the appropriate fillStyle or strokeStyle
    getPattern: function Pattern_getPattern(ctx) {
      error('Should not call Pattern.getStyle: ' + ctx);
    }
  };

  Pattern.parseShading = function Pattern_parseShading(shading, matrix, xref,
                                                       res) {

    var dict = isStream(shading) ? shading.dict : shading;
    var type = dict.get('ShadingType');

    switch (type) {
      case PatternType.AXIAL:
      case PatternType.RADIAL:
        // Both radial and axial shadings are handled by RadialAxial shading.
        return new Shadings.RadialAxial(dict, matrix, xref, res);
      default:
        UnsupportedManager.notify(UNSUPPORTED_FEATURES.shadingPattern);
        return new Shadings.Dummy();
    }
  };
  return Pattern;
})();

var Shadings = {};

// A small number to offset the first/last color stops so we can insert ones to
// support extend.  Number.MIN_VALUE appears to be too small and breaks the
// extend. 1e-7 works in FF but chrome seems to use an even smaller sized number
// internally so we have to go bigger.
Shadings.SMALL_NUMBER = 1e-2;

// Radial and axial shading have very similar implementations
// If needed, the implementations can be broken into two classes
Shadings.RadialAxial = (function RadialAxialClosure() {
  function RadialAxial(dict, matrix, xref, res) {
    this.matrix = matrix;
    this.coordsArr = dict.get('Coords');
    this.shadingType = dict.get('ShadingType');
    this.type = 'Pattern';
    var cs = dict.get('ColorSpace', 'CS');
    cs = ColorSpace.parse(cs, xref, res);
    this.cs = cs;

    var t0 = 0.0, t1 = 1.0;
    if (dict.has('Domain')) {
      var domainArr = dict.get('Domain');
      t0 = domainArr[0];
      t1 = domainArr[1];
    }

    var extendStart = false, extendEnd = false;
    if (dict.has('Extend')) {
      var extendArr = dict.get('Extend');
      extendStart = extendArr[0];
      extendEnd = extendArr[1];
    }

    if (this.shadingType === PatternType.RADIAL &&
       (!extendStart || !extendEnd)) {
      // Radial gradient only currently works if either circle is fully within
      // the other circle.
      var x1 = this.coordsArr[0];
      var y1 = this.coordsArr[1];
      var r1 = this.coordsArr[2];
      var x2 = this.coordsArr[3];
      var y2 = this.coordsArr[4];
      var r2 = this.coordsArr[5];
      var distance = Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
      if (r1 <= r2 + distance &&
          r2 <= r1 + distance) {
        warn('Unsupported radial gradient.');
      }
    }

    this.extendStart = extendStart;
    this.extendEnd = extendEnd;

    var fnObj = dict.get('Function');
    var fn;
    if (isArray(fnObj)) {
      var fnArray = [];
      for (var j = 0, jj = fnObj.length; j < jj; j++) {
        var obj = xref.fetchIfRef(fnObj[j]);
        if (!isPDFFunction(obj)) {
          error('Invalid function');
        }
        fnArray.push(PDFFunction.parse(xref, obj));
      }
      fn = function radialAxialColorFunction(arg) {
        var out = [];
        for (var i = 0, ii = fnArray.length; i < ii; i++) {
          out.push(fnArray[i](arg)[0]);
        }
        return out;
      };
    } else {
      if (!isPDFFunction(fnObj)) {
        error('Invalid function');
      }
      fn = PDFFunction.parse(xref, fnObj);
    }

    // 10 samples seems good enough for now, but probably won't work
    // if there are sharp color changes. Ideally, we would implement
    // the spec faithfully and add lossless optimizations.
    var diff = t1 - t0;
    var step = diff / 10;

    var colorStops = this.colorStops = [];

    // Protect against bad domains so we don't end up in an infinte loop below.
    if (t0 >= t1 || step <= 0) {
      // Acrobat doesn't seem to handle these cases so we'll ignore for
      // now.
      info('Bad shading domain.');
      return;
    }

    for (var i = t0; i <= t1; i += step) {
      var rgbColor = cs.getRgb(fn([i]), 0);
      var cssColor = Util.makeCssRgb(rgbColor);
      colorStops.push([(i - t0) / diff, cssColor]);
    }

    var background = 'transparent';
    if (dict.has('Background')) {
      var rgbColor = cs.getRgb(dict.get('Background'), 0);
      background = Util.makeCssRgb(rgbColor);
    }

    if (!extendStart) {
      // Insert a color stop at the front and offset the first real color stop
      // so it doesn't conflict with the one we insert.
      colorStops.unshift([0, background]);
      colorStops[1][0] += Shadings.SMALL_NUMBER;
    }
    if (!extendEnd) {
      // Same idea as above in extendStart but for the end.
      colorStops[colorStops.length - 1][0] -= Shadings.SMALL_NUMBER;
      colorStops.push([1, background]);
    }

    this.colorStops = colorStops;
  }

  RadialAxial.prototype = {
    getIR: function RadialAxial_getIR() {
      var coordsArr = this.coordsArr;
      var shadingType = this.shadingType;
      var type, p0, p1, r0, r1;
      if (shadingType == PatternType.AXIAL) {
        p0 = [coordsArr[0], coordsArr[1]];
        p1 = [coordsArr[2], coordsArr[3]];
        r0 = null;
        r1 = null;
        type = 'axial';
      } else if (shadingType == PatternType.RADIAL) {
        p0 = [coordsArr[0], coordsArr[1]];
        p1 = [coordsArr[3], coordsArr[4]];
        r0 = coordsArr[2];
        r1 = coordsArr[5];
        type = 'radial';
      } else {
        error('getPattern type unknown: ' + shadingType);
      }

      var matrix = this.matrix;
      if (matrix) {
        p0 = Util.applyTransform(p0, matrix);
        p1 = Util.applyTransform(p1, matrix);
      }

      return ['RadialAxial', type, this.colorStops, p0, p1, r0, r1];
    }
  };

  return RadialAxial;
})();

Shadings.Dummy = (function DummyClosure() {
  function Dummy() {
    this.type = 'Pattern';
  }

  Dummy.prototype = {
    getIR: function Dummy_getIR() {
      return ['Dummy'];
    }
  };
  return Dummy;
})();

function getTilingPatternIR(operatorList, dict, args) {
  var matrix = dict.get('Matrix');
  var bbox = dict.get('BBox');
  var xstep = dict.get('XStep');
  var ystep = dict.get('YStep');
  var paintType = dict.get('PaintType');
  var tilingType = dict.get('TilingType');

  return [
    'TilingPattern', args, operatorList, matrix, bbox, xstep, ystep,
    paintType, tilingType
  ];
}