tianai-captcha-enhanced/tools/icon-render/RenderIcons.java

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 * One-off tool: pre-render emoji icons to PNG assets for IconClickImageCaptchaGenerator.
 * Must run on a machine that has a color/outline emoji font (e.g. Windows Segoe UI Emoji).
 * Output: META-INF/captcha-icons/<name>.png (96x96, white backing disc + glyph).
 *
 * Usage: java tools/icon-render/RenderIcons.java <output-dir>
 */
public class RenderIcons {

    private static final int CANVAS = 96;
    private static final float GLYPH_SIZE = 60f;

    private static final Map<String, String> ICONS = new LinkedHashMap<>() {{
        // fruits
        put("apple", "\uD83C\uDF4E");
        put("banana", "\uD83C\uDF4C");
        put("cherry", "\uD83C\uDF52");
        put("grapes", "\uD83C\uDF47");
        put("lemon", "\uD83C\uDF4B");
        put("orange", "\uD83C\uDF4A");
        put("strawberry", "\uD83C\uDF53");
        put("watermelon", "\uD83C\uDF49");
        // animals
        put("dog", "\uD83D\uDC36");
        put("cat", "\uD83D\uDC31");
        put("mouse", "\uD83D\uDC2D");
        put("hamster", "\uD83D\uDC39");
        put("rabbit", "\uD83D\uDC30");
        put("fox", "\uD83E\uDD8A");
        put("bear", "\uD83D\uDC3B");
        put("panda", "\uD83D\uDC28");
        // sports
        put("soccer", "\u26BD");
        put("basketball", "\uD83C\uDFC0");
        put("tennis", "\uD83C\uDFBE");
        put("volleyball", "\uD83C\uDFD0");
        put("billiards", "\uD83C\uDFB1");
        put("pingpong", "\uD83C\uDFD3");
        put("trophy", "\uD83C\uDFC6");
        put("boxing", "\uD83E\uDD4A");
        // vehicles
        put("car", "\uD83D\uDE97");
        put("taxi", "\uD83D\uDE95");
        put("suv", "\uD83D\uDE99");
        put("bus", "\uD83D\uDE8C");
        put("racecar", "\uD83C\uDFCE");
        put("police", "\uD83D\uDE93");
        put("ambulance", "\uD83D\uDE91");
        put("firetruck", "\uD83D\uDE92");
        // tech
        put("phone", "\uD83D\uDCF1");
        put("laptop", "\uD83D\uDCBB");
        put("desktop", "\uD83D\uDDA5");
        put("printer", "\uD83D\uDDA8");
        put("keyboard", "\u2328");
        put("computer-mouse", "\uD83D\uDDB1");
        put("cd", "\uD83D\uDCBF");
        put("camera", "\uD83D\uDCF7");
    }};

    public static void main(String[] args) throws IOException {
        Path outDir = Paths.get(args.length > 0 ? args[0] : ".");
        Files.createDirectories(outDir);

        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
        Font emojiFont = pickFont(ge);
        System.out.println("Using font: " + emojiFont.getFontName());

        int failures = 0;
        for (Map.Entry<String, String> e : ICONS.entrySet()) {
            BufferedImage img = render(e.getValue(), emojiFont);
            File out = outDir.resolve(e.getKey() + ".png").toFile();
            ImageIO.write(img, "png", out);
            if (emojiFont.canDisplayUpTo(e.getValue()) != -1) {
                System.out.println("[WARN] partial glyph coverage: " + e.getKey());
                failures++;
            }
            System.out.println("OK " + out.getName());
        }
        System.out.println("Done. failures(warn)=" + failures);
    }

    private static Font pickFont(GraphicsEnvironment ge) {
        for (String name : new String[]{"Segoe UI Emoji", "Apple Color Emoji", "Noto Color Emoji", "EmojiOne"}) {
            for (Font f : ge.getAllFonts()) {
                if (f.getFontName().equalsIgnoreCase(name)) {
                    return f.deriveFont(Font.PLAIN, GLYPH_SIZE);
                }
            }
        }
        System.out.println("[WARN] no known emoji font found, falling back to Dialog");
        return new Font(Font.DIALOG, Font.PLAIN, (int) GLYPH_SIZE);
    }

    private static BufferedImage render(String emoji, Font font) {
        BufferedImage img = new BufferedImage(CANVAS, CANVAS, BufferedImage.TYPE_INT_ARGB);
        Graphics2D g = img.createGraphics();
        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
        g.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
        g.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
        try {
            // translucent white backing disc -> keeps icons readable on any photo background
            g.setColor(new Color(255, 255, 255, 216));
            g.fillOval(2, 2, CANVAS - 5, CANVAS - 5);
            g.setColor(new Color(0, 0, 0, 46));
            g.setStroke(new BasicStroke(2f));
            g.drawOval(3, 3, CANVAS - 7, CANVAS - 7);

            g.setColor(Color.BLACK);
            g.setFont(font);
            FontMetrics fm = g.getFontMetrics();
            int x = (CANVAS - fm.stringWidth(emoji)) / 2;
            int y = (CANVAS - fm.getHeight()) / 2 + fm.getAscent();
            g.drawString(emoji, x, y);
        } finally {
            g.dispose();
        }
        return img;
    }
}