Generate icons from a font file

src/io/flutter/utils/IconPreviewGenerator.java

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+/*
+ * Copyright 2021 The Chromium Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+package io.flutter.utils;
+
+import com.intellij.openapi.diagnostic.Logger;
+import com.intellij.util.TripleFunction;
+import io.flutter.FlutterUtils;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import javax.imageio.ImageIO;
+import javax.swing.*;
+import java.awt.*;
+import java.awt.font.FontRenderContext;
+import java.awt.font.LineMetrics;
+import java.awt.geom.AffineTransform;
+import java.awt.geom.Rectangle2D;
+import java.awt.image.BufferedImage;
+import java.io.*;
+import java.util.Properties;
+
+@SuppressWarnings("UseJBColor")
+public class IconPreviewGenerator {
+  private static final Logger LOG = Logger.getInstance(IconPreviewGenerator.class);
+
+  @NotNull final String fontFilePath;
+  int iconSize = 16;
+  int fontSize = 16;
+  @NotNull Color fontColor = Color.gray;
+
+  public IconPreviewGenerator(@NotNull String fontFilePath) {
+    this.fontFilePath = fontFilePath;
+  }
+
+  public IconPreviewGenerator(@NotNull String fontFilePath, int iconSize, int fontSize, @Nullable Color fontColor) {
+    this(fontFilePath);
+    this.iconSize = iconSize;
+    this.fontSize = fontSize;
+    if (fontColor != null) {
+      this.fontColor = fontColor;
+    }
+  }
+
+  public Icon convert(String hexString) {
+    if (hexString.startsWith("0x") || hexString.startsWith("0X")) {
+      hexString = hexString.substring(2);
+    }
+    return convert(Integer.parseInt(hexString, 16));
+  }
+
+  public Icon convert(int code) {
+    return runInGraphicsContext((BufferedImage image, Graphics2D graphics, FontRenderContext frc) -> {
+      char ch = Character.toChars(code)[0];
+      String codepoint = Character.toString(ch);
+
+      drawGlyph(codepoint, graphics, frc);
+      return new ImageIcon(image);
+    });
+  }
+
+  // Given a file at path-to-font-properties in the format generated by tools_metadata (on github),
+  // to generate double-size icons for all glyphs in a font:
+  // IconPreviewGenerator ipg = new IconPreviewGenerator("path-to-ttf-file", 32, 32, Color.black);
+  // ipg.batchConvert("path-to-out-dir", "path-to-font-properties", "@2x");
+  public void batchConvert(@NotNull String outPath, @NotNull String path, @NotNull String suffix) {
+    final String outputPath = outPath.endsWith("/") ? outPath : outPath + "/";
+    //noinspection ResultOfMethodCallIgnored
+    new File(outputPath).mkdirs();
+
+    runInGraphicsContext((BufferedImage image, Graphics2D graphics, FontRenderContext frc) -> {
+      Properties fontMap = new Properties();
+      File file = new File(path);
+      try (InputStream stream = new BufferedInputStream(new FileInputStream(file))) {
+        fontMap.load(stream);
+        for (Object nextKey : fontMap.keySet()) {
+          if (!(nextKey instanceof String)) continue;
+          String codepoint = (String)nextKey;
+          if (!codepoint.endsWith(".codepoint")) continue;
+          String iconName = fontMap.getProperty(codepoint);
+          codepoint = codepoint.substring(0, codepoint.indexOf(".codepoint"));
+          int code = Integer.parseInt(codepoint, 16);
+          char ch = Character.toChars(code)[0];
+          codepoint = Character.toString(ch);
+
+          drawGlyph(codepoint, graphics, frc);
+          ImageIO.write(image, "PNG", new File(outputPath + iconName + suffix + ".png"));
+        }
+      }
+      catch (IOException ex) {
+        FlutterUtils.warn(LOG, ex);
+      }
+      return null;
+    });
+  }
+
+  private Icon runInGraphicsContext(TripleFunction<BufferedImage, Graphics2D, FontRenderContext, Icon> callback) {
+    Icon result = null;
+    Graphics2D graphics = null;
+    //noinspection UndesirableClassUsage
+    BufferedImage image = new BufferedImage(iconSize, iconSize, BufferedImage.TYPE_4BYTE_ABGR);
+    try (InputStream inputStream = new FileInputStream(new File(fontFilePath))) {
+      Font font = Font.createFont(Font.TRUETYPE_FONT, inputStream).deriveFont(Font.PLAIN, fontSize);
+      graphics = image.createGraphics();
+      graphics.setFont(font);
+      graphics.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
+      FontRenderContext frc = new FontRenderContext(new AffineTransform(), true, true);
+      result = callback.fun(image, graphics, frc);
+    }
+    catch (IOException | FontFormatException ex) {
+      FlutterUtils.warn(LOG, ex);
+    }
+    finally {
+      if (graphics != null) graphics.dispose();
+    }
+    return result;
+  }
+
+  private void drawGlyph(String codepoint, Graphics2D graphics, FontRenderContext frc) {
+    Font font = graphics.getFont();
+    Rectangle2D rect = font.getStringBounds(codepoint, frc);
+    LineMetrics metrics = font.getLineMetrics(codepoint, frc);
+    float lineHeight = metrics.getHeight();
+    float ascent = metrics.getAscent();
+    float width = (float)rect.getWidth();
+    float x0 = (iconSize - width) / 2.0f;
+    float y0 = (iconSize - lineHeight) / 2.0f + ascent + (lineHeight - ascent) / 2.0f;
+
+    graphics.setComposite(AlphaComposite.Clear);
+    graphics.fillRect(0, 0, iconSize, iconSize);
+
+    graphics.setComposite(AlphaComposite.Src);
+    graphics.setColor(fontColor);
+    graphics.drawString(codepoint, x0, y0);
+  }
+}