libjava/classpath/gnu/java/awt/font/opentype/truetype/TrueTypeScaler.java

   1 /* TrueTypeScaler.java -- Font scaler for TrueType outlines.
   2    Copyright (C) 2006 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38 package gnu.java.awt.font.opentype.truetype;
  39
  40 import gnu.java.awt.font.opentype.Scaler;
  41
  42 import java.awt.FontFormatException;
  43 import java.awt.geom.AffineTransform;
  44 import java.awt.geom.GeneralPath;
  45 import java.awt.geom.Point2D;
  46 import java.nio.ByteBuffer;
  47
  48
  49 /**
  50  * A scaler for fonts whose outlines are described in the TrueType
  51  * format.
  52  *
  53  * <p><b>Lack of Thread Safety:</b> Font scalers are intentionally
  54  * <i>not</i> safe to access from multiple concurrent threads.
  55  * Synchronization needs to be performed externally. Usually, the font
  56  * that uses this scaler already has obtained a lock before calling
  57  * the scaler.
  58  *
  59  * @author Sascha Brawer (brawer@dandelis.ch)
  60  */
  61 public final class TrueTypeScaler
  62   extends Scaler
  63 {
  64   /**
  65    * The TrueType or OpenType table that contains the glyph outlines.
  66    */
  67   private ByteBuffer glyfTable;
  68
  69
  70   /**
  71    * A helper object for loading glyph outlines.
  72    */
  73   private GlyphLoader glyphLoader;
  74
  75
  76   /**
  77    * A helper object for measuring the advance width and height of a
  78    * glyph.
  79    */
  80   private final GlyphMeasurer glyphMeasurer;
  81
  82   private final Zone glyphZone;
  83
  84
  85   /**
  86    * The number of units per em. A typical value is 2048, but some
  87    * font use other numbers as well.
  88    */
  89   private int unitsPerEm;
  90
  91
  92   /**
  93    * Constructs a new TrueTypeScaler.
  94    *
  95    * @param unitsPerEm the number of font units per em. This value can
  96    * be retrieved from the font&#x2019;s <code>head</code> table.
  97    *
  98    * @param maxp the <code>maxp</code> table of the font, which
  99    * contains various constants needed for setting up the virtual
 100    * machine that interprets TrueType bytecodes.
 101    *
 102    * @param controlValueTable the <code>cvt</code> table of the font,
 103    * which contains the initial values of the control value table.
 104    *
 105    * @param fpgm the <code>fpgm</code> table of the font, which
 106    * contains a font program that is executed exactly once.  The
 107    * purpose of the font program is to define functions and to patch
 108    * the interpreter.
 109    *
 110    * @param locaFormat the format of the <code>loca</code> table.  The
 111    * value must be 0 for two-byte offsets, or 1 for four-byte
 112    * offsets. TrueType and OpenType fonts indicate the format in the
 113    * <code>indexToLoc</code> field of the <a href=
 114    * "http://partners.adobe.com/asn/tech/type/opentype/head.html"
 115    * >font header</a>.
 116    *
 117    * @param loca the <code>loca</code> table of the font, which
 118    * contains for each glyph the offset of its outline data
 119    * in <code>glyf</code>.
 120    *
 121    * @param glyf the <code>glyf</code> table of the font, which
 122    * contains the outline data for all glyphs in the font.
 123    *
 124    * @param preProgram the <code>prep</code> table of the font, which
 125    * contains a program that is executed whenever the point size or
 126    * the device transform have changed.  This program is called
 127    * pre-program because it gets executed before the instructions of
 128    * the individual glyphs.  If the font does not contain a
 129    * pre-program, pass <code>null</code>.
 130    *
 131    * @throws FontFormatException if <code>format</code> is neither 0
 132    * nor 1.
 133    */
 134   public TrueTypeScaler(int unitsPerEm,
 135                         ByteBuffer hhea,
 136                         ByteBuffer htmx,
 137                         ByteBuffer vhea,
 138                         ByteBuffer vtmx,
 139                         ByteBuffer maxp,
 140                         ByteBuffer controlValueTable,
 141                         ByteBuffer fpgm,
 142                         int locaFormat, ByteBuffer loca,
 143                         ByteBuffer glyf,
 144                         ByteBuffer preProgram)
 145     throws FontFormatException
 146   {
 147     int maxContours, maxPoints;
 148     VirtualMachine vm;
 149
 150     maxContours = Math.max(/* maxContours */ (int) maxp.getChar(8),
 151                            /* maxCompositeContours */ (int) maxp.getChar(12))
 152       + /* fix for some broken fonts */ 8;
 153     maxPoints = Math.max(/* maxPoints */ (int) maxp.getChar(6),
 154                          /* maxCompositePoints */ (int) maxp.getChar(10))
 155       + /* fix for some broken fonts */ 12;
 156
 157
 158     glyphZone = new Zone(maxPoints + /* four phantom points */ 4);
 159     this.glyfTable = glyf;
 160     vm = new VirtualMachine(unitsPerEm, maxp,
 161                             controlValueTable, fpgm,
 162                             preProgram);
 163
 164     GlyphLocator locator = GlyphLocator.forTable(locaFormat, loca, glyf);
 165     glyphMeasurer = new GlyphMeasurer(hhea, htmx, vhea, vtmx);
 166     glyphLoader = new GlyphLoader(locator, vm, unitsPerEm,
 167                                   maxContours, maxPoints,
 168                                   glyphMeasurer);
 169
 170     this.unitsPerEm = unitsPerEm;
 171   }
 172
 173
 174   /**
 175    * Retrieves the scaled outline of a glyph, adjusting control points
 176    * to the raster grid if necessary.
 177    *
 178    * @param glyphIndex the glyph number whose outline is retrieved.
 179    *
 180    * @param pointSize the point size for the glyph.
 181    *
 182    * @param deviceTransform an affine transformation for the device.
 183    *
 184    * @param antialias whether or not the rasterizer will perform
 185    * anti-aliasing on the returned path.
 186    *
 187    * @param fractionalMetrics <code>false</code> for adjusting glyph
 188    * positions to the raster grid of device space.
 189    */
 190   public GeneralPath getOutline(int glyphIndex,
 191                                 float pointSize,
 192                                 AffineTransform deviceTransform,
 193                                 boolean antialias,
 194                                 boolean fractionalMetrics)
 195   {
 196     glyphLoader.loadGlyph(glyphIndex, pointSize, deviceTransform,
 197                           antialias, glyphZone);
 198     return glyphZone.getPath();
 199   }
 200
 201
 202   /**
 203    * Determines the advance width and height for a glyph.
 204    *
 205    * @param glyphIndex the glyph whose advance width and height is to
 206    * be determined.
 207    *
 208    * @param pointSize the point size of the font.
 209    *
 210    * @param transform a transform that is applied in addition to
 211    * scaling to the specified point size. This is often used for
 212    * scaling according to the device resolution. Those who lack any
 213    * aesthetic sense may also use the transform to slant or stretch
 214    * glyphs.
 215    *
 216    * @param antialias <code>true</code> for anti-aliased rendering,
 217    * <code>false</code> for normal rendering. For hinted fonts,
 218    * this parameter may indeed affect the result.
 219    *
 220    * @param fractionalMetrics <code>true</code> for fractional metrics,
 221    * <code>false</code> for rounding the result to a pixel boundary.
 222    *
 223    * @param horizontal <code>true</code> for horizontal line layout,
 224    * <code>false</code> for vertical line layout.
 225    *
 226    * @param advance a point whose <code>x</code> and <code>y</code>
 227    * fields will hold the advance in each direction. It is possible
 228    * that both values are non-zero, for example if
 229    * <code>transform</code> is a rotation, or in the case of Urdu
 230    * fonts.
 231    */
 232   public void getAdvance(int glyphIndex,
 233                          float pointSize,
 234                          AffineTransform transform,
 235                          boolean antialias,
 236                          boolean fractionalMetrics,
 237                          boolean horizontal,
 238                          Point2D advance)
 239   {
 240     double x, y;
 241     double scaleFactor = (double) pointSize / unitsPerEm;
 242
 243     /* FIXME: Should grid-fit if needed. Also, use cache if present
 244      * in the font.
 245      */
 246     advance.setLocation(
 247       scaleFactor * glyphMeasurer.getAdvanceWidth(glyphIndex, horizontal),
 248       scaleFactor * glyphMeasurer.getAdvanceHeight(glyphIndex, horizontal));
 249
 250     transform.transform(advance, advance);
 251   }
 252
 253
 254   /**
 255    * Scales a value from font units to pixels, given the point size
 256    * and the transform.
 257    *
 258    * @param pointSize the point size of the font.
 259    *
 260    * @param transform a transform that is applied in addition to
 261    * scaling to the specified point size. This is often used for
 262    * scaling according to the device resolution.
 263    *
 264    * @param fractionalMetrics <code>true</code> for fractional
 265    * metrics, <code>false</code> for rounding the result to a pixel
 266    * boundary.
 267    *
 268    * @param horizontal <code>true</code> if the <code>funits</code>
 269    * value is along the x axis, <code>false</code> if it is along the
 270    * y axis.
 271    */
 272   private float scaleFromFUnits(int funits,
 273                                 float pointSize,
 274                                 AffineTransform transform,
 275                                 boolean fractionalMetrics,
 276                                 boolean horizontal)
 277   {
 278     double s;
 279
 280     s = (double) pointSize / unitsPerEm;
 281     if (transform != null)
 282       s *= horizontal ? transform.getScaleY() : transform.getScaleX();
 283     s *= funits;
 284     if (!fractionalMetrics)
 285       s = Math.round(s);
 286     return (float) s;
 287   }
 288
 289
 290   /**
 291    * Determines the distance between the base line and the highest
 292    * ascender.
 293    *
 294    * @param pointSize the point size of the font.
 295    *
 296    * @param transform a transform that is applied in addition to
 297    * scaling to the specified point size. This is often used for
 298    * scaling according to the device resolution. Those who lack any
 299    * aesthetic sense may also use the transform to slant or stretch
 300    * glyphs.
 301    *
 302    * @param antialias <code>true</code> for anti-aliased rendering,
 303    * <code>false</code> for normal rendering. For hinted fonts,
 304    * this parameter may indeed affect the result.
 305    *
 306    * @param fractionalMetrics <code>true</code> for fractional metrics,
 307    * <code>false</code> for rounding the result to a pixel boundary.
 308    *
 309    * @param horizontal <code>true</code> for horizontal line layout,
 310    * <code>false</code> for vertical line layout.
 311    *
 312    * @return the ascent, which usually is a positive number.
 313    */
 314   public float getAscent(float pointSize,
 315                          AffineTransform transform,
 316                          boolean antialias,
 317                          boolean fractionalMetrics,
 318                          boolean horizontal)
 319   {
 320     /* Note that the ascent is orthogonal to the direction of line
 321      * layout: If the line direction is horizontal, the measurement of
 322      * ascent is along the vertical axis, and vice versa.
 323      */
 324     return scaleFromFUnits(glyphMeasurer.getAscent(horizontal),
 325                            pointSize,
 326                            transform,
 327                            fractionalMetrics,
 328                            /* reverse */ !horizontal);
 329   }
 330
 331
 332   /**
 333    * Determines the distance between the base line and the lowest
 334    * descender.
 335    *
 336    * @param pointSize the point size of the font.
 337    *
 338    * @param transform a transform that is applied in addition to
 339    * scaling to the specified point size. This is often used for
 340    * scaling according to the device resolution. Those who lack any
 341    * aesthetic sense may also use the transform to slant or stretch
 342    * glyphs.
 343    *
 344    * @param antialiased <code>true</code> for anti-aliased rendering,
 345    * <code>false</code> for normal rendering. For hinted fonts,
 346    * this parameter may indeed affect the result.
 347    *
 348    * @param fractionalMetrics <code>true</code> for fractional metrics,
 349    * <code>false</code> for rounding the result to a pixel boundary.
 350    *
 351    * @param horizontal <code>true</code> for horizontal line layout,
 352    * <code>false</code> for vertical line layout.
 353    *
 354    * @return the descent, which usually is a nagative number.
 355    */
 356   public float getDescent(float pointSize,
 357                           AffineTransform transform,
 358                           boolean antialiased,
 359                           boolean fractionalMetrics,
 360                           boolean horizontal)
 361   {
 362     /* Note that the descent is orthogonal to the direction of line
 363      * layout: If the line direction is horizontal, the measurement of
 364      * descent is along the vertical axis, and vice versa.
 365      */
 366     return scaleFromFUnits(glyphMeasurer.getDescent(horizontal),
 367                            pointSize,
 368                            transform,
 369                            fractionalMetrics,
 370                            /* reverse */ !horizontal);
 371   }
 372 }