Example for glyph positioning

examples/src/main/java/org/apache/pdfbox/examples/pdmodel/glyphposition/CharactersAndPositions.java

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ *
+ * Volker Kunert 2026
+ */
+
+package org.apache.pdfbox.examples.pdmodel.glyphposition;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Stores sublists of characters and positions in a list
+ * Helper class for GlyphPositioner
+ */
+public class CharactersAndPositions {
+    private final ArrayList<Object> list = new ArrayList<>();
+
+    /**
+     * Adds a character
+     *
+     * @param ch to be added
+     */
+    public void add(char ch) {
+        Object last = !list.isEmpty() ? list.get(list.size() - 1) : null;
+        GlyphSubList glyphSubList;
+        if (!(last instanceof GlyphSubList)) {
+            glyphSubList = new GlyphSubList();
+            list.add(glyphSubList);
+        } else {
+            glyphSubList = (GlyphSubList) last;
+        }
+        glyphSubList.add(ch);
+    }
+
+    /**
+     * Add a position
+     *
+     * @param position to be added
+     */
+    public void add(Float position) {
+        list.add(position);
+    }
+
+    /**
+     * Checks if the list is empty
+     *
+     * @return true if it is empty
+     */
+    public boolean isEmpty() {
+        return list.isEmpty();
+    }
+
+    /**
+     * Clears the list
+     */
+    public void clear() {
+        list.clear();
+    }
+
+    /**
+     * Converts CharactersAndPositions to a list of objects (GlyphSubList and Float)
+     *
+     * @return the list
+     */
+    public List<Object> toList() {
+        return Collections.unmodifiableList(list);
+    }
+
+    /**
+     * Converts CharactersAndPositions to an array of objects (GlyphSubList and Float)
+     *
+     * @return the array
+     */
+    public Object[] toArray() {
+        return Collections.unmodifiableList(list).toArray();
+    }
+
+    /**
+     * Sublist to store adjacent glyphs
+     */
+    public static class GlyphSubList extends ArrayList<Character> {
+    }
+}

examples/src/main/java/org/apache/pdfbox/examples/pdmodel/glyphposition/GlyphPositioner.java

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ *
+ * Volker Kunert 2026
+ */
+
+package org.apache.pdfbox.examples.pdmodel.glyphposition;
+
+import org.apache.pdfbox.pdmodel.PDPageContentStream;
+import org.apache.pdfbox.pdmodel.font.PDType0Font;
+
+
+import java.awt.Font;
+import java.awt.font.FontRenderContext;
+import java.awt.font.GlyphVector;
+import java.awt.geom.AffineTransform;
+import java.awt.geom.Point2D;
+import java.io.IOException;
+import java.io.InputStream;
+import java.text.AttributedString;
+import java.text.Bidi;
+import java.util.ArrayList;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * Character positioning
+ * (No glyph reordering or substitution)
+ */
+public class GlyphPositioner {
+    private final Map<PDType0Font, Font> awtFontMap = new ConcurrentHashMap<>();
+    private final PDPageContentStream contentStream;
+    private PDType0Font font;
+    private float fontSize;
+
+    /**
+     * Constructs a GlyphPositioner
+     *
+     */
+    public GlyphPositioner(PDPageContentStream contentStream) {
+        this.contentStream = contentStream;
+    }
+
+    /**
+     * Checks if the glyphVector contains adjustments
+     * that make advanced glyph layout necessary
+     *
+     * @param glyphVector glyph vector containing the positions
+     * @return true if the glyphVector contains adjustments
+     */
+    private static boolean hasAdjustments(GlyphVector glyphVector) {
+        boolean retVal = false;
+        float lastX = 0f;
+        float lastY = 0f;
+
+        for (int i = 0; i < glyphVector.getNumGlyphs(); i++) {
+            Point2D p = glyphVector.getGlyphPosition(i);
+            float dx = (float) p.getX() - lastX;
+            float dy = (float) p.getY() - lastY;
+
+            float ax = (i == 0) ? 0.0f : glyphVector.getGlyphMetrics(i - 1).getAdvanceX();
+            float ay = (i == 0) ? 0.0f : glyphVector.getGlyphMetrics(i - 1).getAdvanceY();
+
+            if (dx != ax || dy != ay) {
+                retVal = true;
+                break;
+            }
+            lastX = (float) p.getX();
+            lastY = (float) p.getY();
+        }
+        return retVal;
+    }
+
+    /**
+     * Loads the AWT font needed
+     *
+     * @param pdType0Font PDFBOX font
+     * @param inputStream of the font file
+     * @throws RuntimeException if font can not be loaded
+     */
+    public void loadAwtFont(PDType0Font pdType0Font, InputStream inputStream) {
+        Font awtFont = null;
+        try {
+            if (!awtFontMap.containsKey(pdType0Font)) {
+                awtFont = Font.createFont(java.awt.Font.TRUETYPE_FONT, inputStream);
+                if (awtFont == null) {
+                    throw new RuntimeException("Font is null");
+                }
+                awtFontMap.put(pdType0Font, awtFont);
+            }
+        } catch (Exception e) {
+            throw new RuntimeException(String.format("AWT Font creation failed for %s.", pdType0Font.getName()), e);
+        } finally {
+            try {
+                inputStream.close();
+            } catch (Exception e) {
+                //ignore
+            }
+        }
+    }
+
+    /**
+     * Computes glyph positioning
+     *
+     * @param text input text
+     * @return glyph vector containing reordered text, width and positioning info
+     */
+    public GlyphVector computeGlyphVector(String text) {
+        char[] chars = text.toCharArray();
+
+        FontRenderContext fontRenderContext = new FontRenderContext(new AffineTransform(), false, true);
+        // use fractional metrics
+        AttributedString as = new AttributedString(text);
+        Bidi bidi = new Bidi(as.getIterator());
+        int localFlags = bidi.isLeftToRight() ? java.awt.Font.LAYOUT_LEFT_TO_RIGHT : java.awt.Font.LAYOUT_RIGHT_TO_LEFT;
+
+        java.awt.Font awtFont = awtFontMap.get(font).deriveFont(fontSize);
+
+        return awtFont.layoutGlyphVector(fontRenderContext, chars, 0, chars.length, localFlags);
+    }
+
+
+    /**
+     * Sets the font and fontSize
+     *
+     * @param font     to be set
+     * @param fontSize font size
+     */
+    public void setFontAndSize(PDType0Font font, float fontSize) {
+        this.font = font;
+        this.fontSize = fontSize;
+    }
+
+    /**
+     * Shows a text using glyph positioning (if needed)
+     *
+     * @param text text to show
+     * @throws IOException in case of IO-error
+     */
+    public void showText(String text) throws IOException {
+        GlyphVector glyphVector = computeGlyphVector(text);
+        if (!hasAdjustments(glyphVector)) {
+            contentStream.showText(text);
+            return;
+        }
+
+        final float delta = 1e-5f;
+        final float factorX = 1000f / fontSize;
+        float lastX = 0f;
+        char[] characters = text.toCharArray();
+
+        CharactersAndPositions ga = new CharactersAndPositions();
+
+        for (int i = 0; i < glyphVector.getNumGlyphs(); i++) {
+            Point2D p = glyphVector.getGlyphPosition(i);
+            float ax = (i == 0) ? 0.0f : glyphVector.getGlyphMetrics(i - 1).getAdvanceX();
+            float dx = (float) p.getX() - lastX - ax;
+            float py = (float) p.getY();
+
+            if (Math.abs(py) >= delta) {
+                if (!ga.isEmpty()) {
+                    showCharactersWithPositioning(contentStream, ga);
+                    ga.clear();
+                }
+                contentStream.setTextRise(-py);
+            }
+            if (Math.abs(dx) >= delta) {
+                ga.add(-dx * factorX);
+            }
+
+            // There is no method in PDPageContentStream to position
+            // glyphs using the glyph id, so we have to use the
+            // characters.
+            ga.add(characters[i]);
+            if (Math.abs(py) >= delta) {
+                showCharactersWithPositioning(contentStream, ga);
+                ga.clear();
+                contentStream.setTextRise(0.0f);
+            }
+            lastX = (float) p.getX();
+        }
+        // adjust the end position
+        Point2D p = glyphVector.getGlyphPosition(glyphVector.getNumGlyphs());
+        float ax = (glyphVector.getNumGlyphs() == 0) ? 0.0f
+                : glyphVector.getGlyphMetrics(glyphVector.getNumGlyphs() - 1).getAdvanceX();
+        float dx = (float) p.getX() - lastX - ax;
+        if (Math.abs(dx) >= delta) {
+            ga.add(-dx * factorX);
+        }
+        showCharactersWithPositioning(contentStream, ga);
+        ga.clear();
+    }
+
+    /**
+     * Show the given characters at the given positions
+     * @param contentStream to show the text
+     * @param charactersAndPositions List of characters and positions
+     * @throws IOException if an IO error occurs
+     */
+    public void showCharactersWithPositioning(PDPageContentStream contentStream, CharactersAndPositions charactersAndPositions) throws IOException {
+        ArrayList<Object> textWithPositioning = new ArrayList<>();
+        for (Object obj : charactersAndPositions.toArray()) {
+            if (obj instanceof CharactersAndPositions.GlyphSubList) {
+                CharactersAndPositions.GlyphSubList glyphSubList = (CharactersAndPositions.GlyphSubList) obj;
+                StringBuilder sb = new StringBuilder();
+                for (Object o : glyphSubList.toArray()) {
+                    sb.append(o);
+                }
+                textWithPositioning.add(sb.toString());
+            } else if (obj instanceof Float) {
+                textWithPositioning.add(obj);
+            } else {
+                if (obj == null) {
+                    throw new NullPointerException("Argument contains null entry");
+                }
+                throw new IllegalArgumentException("Argument must consist of array of Float and CharactersAndPositions.GlyphSubList types, not " + obj.getClass().getName());
+            }
+        }
+        contentStream.showTextWithPositioning(textWithPositioning.toArray());
+    }
+}