Allow to limit characters to be placed in generated header file.

src/main/java/com/arcao/fontcreator/ArgumentParser.java

@@ -21,6 +21,7 @@ public class ArgumentParser {
     private final OptionSpec<File> outputFile;
     private final OptionSpec<String> font;
     private final OptionSpec<Integer> yoffset;
+    private final OptionSpec<String> characters;
 
     public ArgumentParser() {
         help = parser.acceptsAll(asList("h", "help"), "display this help and exit").forHelp();
@@ -31,6 +32,7 @@ public ArgumentParser() {
         charset = parser.acceptsAll(asList("c", "charset"), "font table index charset").withOptionalArg().defaultsTo("iso-8859-1").ofType(String.class);
         outputFile = parser.acceptsAll(asList("o", "output"), "write .h font table to file instead to StdOut").withOptionalArg().ofType(File.class);
         font = parser.nonOptions("system font name or path to font file to be processed").describedAs("FONT").ofType(String.class);
+        characters = parser.acceptsAll(asList("a", "characters"), "characters to include").withRequiredArg().defaultsTo("").ofType(String.class);
     }
 
     public Arguments parse(String args[]) throws OptionException {
@@ -76,6 +78,11 @@ public File outputFile() {
             public String font() {
                 return options.valueOf(font);
             }
+
+            @Override
+            public String characters() {
+                return options.valueOf(characters);
+            }
         };
     }
 

src/main/java/com/arcao/fontcreator/Arguments.java

@@ -19,5 +19,6 @@ interface Arguments {
     String font();
 
     int yoffset();
-
+
+    String characters();
 }

src/main/java/com/arcao/fontcreator/FontConverterV3.java

@@ -19,8 +19,8 @@ Based on squix78 implementation (MIT License) from:
 
 public class FontConverterV3 {
 
-    private static final int END_CHAR = 256;
-    private static final int START_CHAR = 32;
+    private int endChar = 256;
+    private int startChar = 32;
 
     private Graphics2D g;
     private FontMetrics fontMetrics;
@@ -44,20 +44,26 @@ public FontConverterV3(Font font, Charset charset) {
         this.charset = charset;
     }
 
-    public void printFontData(StringBuilder builder, int yoffset) {
+    public void printFontData(StringBuilder builder, int yoffset, String characters) {
+        calculateStartEnd(characters);
 		this.yoffset=yoffset;
-        List<LetterData> letterList = produceLetterDataList();
+        List<LetterData> letterList = produceLetterDataList(characters);
 
         String fontName = g.getFont().getFontName().replaceAll("[\\s\\-\\.]", "_") + "_"
                 + getFontStyle() + "_" + g.getFont().getSize();
         builder.append("// Font table version: 3\n");
         builder.append("// Created by FontCreator (https://github.com/arcao/esp8266-oled-ssd1306-font-creator.\n");
         builder.append("// In case of problems make sure that you are using the font file with the correct version!\n");
-        builder.append(String.format("const char %s[] PROGMEM = {\n", fontName));
+        if (characters != null && !characters.isEmpty()) {
+            builder.append("// contains only \"");
+            builder.append(characters);
+            builder.append("\"\n");
+        }
+        builder.append(String.format("const uint8_t %s[] PROGMEM = {\n", fontName));
         writeHexValue(builder, "Width", getMaxCharWidth());
         writeHexValue(builder, "Height", getMaxCharHeight());
-        writeHexValue(builder, "First Char", START_CHAR);
-        writeHexValue(builder, "Numbers of Chars", END_CHAR - START_CHAR);
+        writeHexValue(builder, "First Char", startChar);
+        writeHexValue(builder, "Numbers of Chars", endChar - startChar);
         builder.append("\n");
         builder.append("\t// Jump Table:\n");
 
@@ -80,7 +86,7 @@ public void printFontData(StringBuilder builder, int yoffset) {
         letterList.stream().filter(LetterData::isVisible).forEach(letter -> {
             builder.append("\t");
             builder.append(letter.toString());
-            if ((int) letter.getCode() != END_CHAR - 1) {
+            if ((int) letter.getCode() != endChar - 1) {
                 builder.append(",");
             }
             builder.append(String.format("\t// %d\n", (int) letter.getCode()));
@@ -89,17 +95,20 @@ public void printFontData(StringBuilder builder, int yoffset) {
         builder.append("};\n");
     }
 
-    private List<LetterData> produceLetterDataList() {
-        List<LetterData> letterDataList = new ArrayList<>(END_CHAR - START_CHAR);
-        for (int i = START_CHAR; i < END_CHAR; i++) {
+    private List<LetterData> produceLetterDataList(String characters) {
+        List<LetterData> letterDataList = new ArrayList<>(endChar - startChar);
+        for (int i = startChar; i < endChar; i++) {
             char ch;
             if (charset == null) {
                 ch = (char) i;
             } else {
                 ch = new String(new byte[]{(byte) (i & 0xFF)}, charset).charAt(0);
             }
-
-            letterDataList.add(createLetterData(ch));
+            LetterData letter = createLetterData(ch);
+            letterDataList.add(letter);
+            if (characters != null && !characters.isEmpty() && characters.indexOf(ch) < 0) {
+                letter.visible = false;
+            }
         }
         return letterDataList;
     }
@@ -187,7 +196,7 @@ private void writeHexValue(StringBuilder builder, String label, int value) {
 
     private int getMaxCharWidth() {
         int maxWidth = 0;
-        for (int i = START_CHAR; i < END_CHAR; i++) {
+        for (int i = startChar; i < endChar; i++) {
             maxWidth = Math.max(maxWidth, fontMetrics.charWidth((char) i));
         }
         return maxWidth;
@@ -197,6 +206,32 @@ private int getMaxCharHeight() {
         return fontMetrics.getMaxAscent() + fontMetrics.getMaxDescent() + fontMetrics.getLeading();
     }
 
+    private void calculateStartEnd(String characters) {
+        if (characters != null && !characters.isEmpty()) {
+            startChar = 255;
+            endChar = 0;
+            for (int i = 0; i < characters.length(); i++) {
+                int idx = characterTargetIndex(characters.charAt(i));
+                if (idx < startChar) {
+                    startChar = idx;
+                }
+                if (idx >= endChar) {
+                    endChar = idx + 1;
+                }
+            }
+        }
+    }
+
+    private int characterTargetIndex(char c) {
+        int ch;
+        if (charset == null) {
+            ch = c;
+        } else {
+            ch = Character.toString(c).getBytes(charset)[0] & 0xFF;
+        }
+        return ch;
+    }
+
     private class LetterData {
 
         private char code;
@@ -243,4 +278,4 @@ public String toString() {
         }
     }
 
-}
+}

src/main/java/com/arcao/fontcreator/FontCreator.java

@@ -63,7 +63,7 @@ public static void main(String args[]) {
             FontConverterV3 fontConverter = new FontConverterV3(font, charset);
 
             StringBuilder builder = new StringBuilder();
-            fontConverter.printFontData(builder, arguments.yoffset());
+            fontConverter.printFontData(builder, arguments.yoffset(), arguments.characters());
 
             PrintStream out = System.out;
             if (arguments.outputFile() != null) {