spring-ai/multimodal/src/main/java/com/ankurm/multimodal/ReceiptImages.java

package com.ankurm.multimodal;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.imageio.ImageIO;

/**
 * Draws a receipt as a PNG so the whole pipeline has a real image to chew on. Deterministic: the
 * same receipt and the same {@link Look} always produce the same bytes (the noise uses a seeded
 * {@link Random}).
 */
public final class ReceiptImages {

    /** How the "photo" was taken. {@code scale} shrinks it, {@code noise} speckles it, {@code degrees} tilts it. */
    public record Look(String name, double scale, double noise, double degrees) {

        public static final Look CLEAN = new Look("clean", 1.0, 0.0, 0.0);
        public static final Look SMALL = new Look("small (1/3 size)", 0.33, 0.0, 0.0);
        public static final Look NOISY = new Look("noisy", 1.0, 0.25, 0.0);
        public static final Look TILTED = new Look("tilted 4 degrees", 1.0, 0.0, 4.0);
    }

    private ReceiptImages() {
    }

    public static List<String> text(Receipt r) {
        List<String> t = new ArrayList<>();
        t.add(r.merchant());
        t.add(r.date().toString());
        t.add("CURRENCY: " + r.currency());
        t.add("--------------------------------");
        for (Receipt.Line l : r.items()) {
            t.add(String.format("%-14s %d x %s %s", l.description(), l.quantity(), l.unitPrice().toPlainString(),
                    l.lineTotal().toPlainString()));
        }
        t.add("--------------------------------");
        t.add("SUBTOTAL " + r.subtotal().toPlainString());
        t.add("TAX " + r.tax().toPlainString());
        t.add("TOTAL " + r.total().toPlainString());
        return t;
    }

    public static byte[] png(Receipt r, Look look) {
        List<String> lines = text(r);
        int base = 30;
        int w = 640;
        int h = 60 + lines.size() * (base + 12);
        BufferedImage page = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        Graphics2D g = page.createGraphics();
        g.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, w, h);
        g.setColor(Color.BLACK);
        g.setFont(new Font(Font.MONOSPACED, Font.PLAIN, base));
        int y = 50;
        for (String s : lines) {
            g.drawString(s, 20, y);
            y += base + 12;
        }
        g.dispose();
        BufferedImage out = page;
        if (look.degrees() != 0) {
            BufferedImage rot = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
            Graphics2D rg = rot.createGraphics();
            rg.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
            rg.setColor(Color.WHITE);
            rg.fillRect(0, 0, w, h);
            rg.transform(AffineTransform.getRotateInstance(Math.toRadians(look.degrees()), w / 2.0, h / 2.0));
            rg.drawImage(page, 0, 0, null);
            rg.dispose();
            out = rot;
        }
        if (look.scale() != 1.0) {
            int nw = (int) Math.round(w * look.scale());
            int nh = (int) Math.round(h * look.scale());
            BufferedImage small = new BufferedImage(nw, nh, BufferedImage.TYPE_INT_RGB);
            Graphics2D sg = small.createGraphics();
            sg.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
            sg.drawImage(out, 0, 0, nw, nh, null);
            sg.dispose();
            out = small;
        }
        if (look.noise() > 0) {
            Random rnd = new Random(42);
            for (int x = 0; x < out.getWidth(); x++) {
                for (int yy = 0; yy < out.getHeight(); yy++) {
                    if (rnd.nextDouble() < look.noise()) {
                        out.setRGB(x, yy, rnd.nextBoolean() ? 0x000000 : 0xFFFFFF);
                    }
                }
            }
        }
        try (ByteArrayOutputStream bos = new ByteArrayOutputStream()) {
            ImageIO.write(out, "png", bos);
            return bos.toByteArray();
        } catch (IOException e) {
            throw new IllegalStateException(e);
        }
    }
}