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#1784 add random fingerprint generator
Usage: * `faker.fingerprint().png()` * `faker.fingerprint().png(300, 200, ARCH)` * `faker.fingerprint().base64()` * `faker.fingerprint().base64(800, 800, LOOP)`
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‎README.md‎

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@@ -345,6 +345,7 @@ The list below is not complete and shows only a part of available providers. To
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* File
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* Final Space
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* Finance
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* Fingerprint
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* Food
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* Formula 1 (:racing_car:)
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* Friends

‎docs/documentation/providers.md‎

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| [Final Space](https://javadoc.io/doc/net.datafaker/datafaker/latest/net/datafaker/providers/entertainment/FinalSpace.html) | Final Space is an adult animated space opera comedy drama television series. | Entertainment | 1.6.0 |
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| [Finance](https://javadoc.io/doc/net.datafaker/datafaker/latest/net/datafaker/providers/base/Finance.html) | | Base | 0.8.0 |
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| [Financial Terms](https://javadoc.io/doc/net.datafaker/datafaker/latest/net/datafaker/providers/base/FinancialTerms.html) | Provides financial terms. | Base | 2.4.0 |
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| [Fingerprint](https://javadoc.io/doc/net.datafaker/datafaker/latest/net/datafaker/providers/base/Fingerprint.html) | Provides random fingerprint generation. | Base | 2.6.0 |
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| [Food](https://javadoc.io/doc/net.datafaker/datafaker/latest/net/datafaker/providers/food/Food.html) | | Food | 0.8.0 |
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| [Football](https://javadoc.io/doc/net.datafaker/datafaker/latest/net/datafaker/providers/sport/Football.html) | | Sport | 1.5.0 |
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| [Formula1](https://javadoc.io/doc/net.datafaker/datafaker/latest/net/datafaker/providers/sport/Formula1.html) | | Sport | 1.2.0 |

‎src/main/java/net/datafaker/providers/base/BaseProviders.java‎

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return getProvider(FinancialTerms.class, FinancialTerms::new);
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}
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default Fingerprint fingerprint() {
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return getProvider(Fingerprint.class, Fingerprint::new);
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}
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default FunnyName funnyName() {
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return getProvider(FunnyName.class, FunnyName::new);
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}

‎src/main/java/net/datafaker/providers/base/Fingerprint.java‎

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package net.datafaker.providers.base;
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import javax.imageio.ImageIO;
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import java.awt.image.BufferedImage;
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import java.io.ByteArrayOutputStream;
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import java.io.IOException;
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import java.util.Base64;
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/**
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* Generates synthetic fingerprint images.
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* <p>
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* The generated images mimic the three standard fingerprint pattern types:
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* whorl (spiral ridges), loop (ridges that loop around a core), and arch
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* (ridges that arch over the centre). A random pattern is chosen unless one
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* is supplied explicitly.
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*
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* @since 2.6.0
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*/
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public class Fingerprint extends AbstractProvider<BaseProviders> {
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private static final int DEFAULT_WIDTH = 200;
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private static final int DEFAULT_HEIGHT = 250;
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private static final double TWO_PI = 2 * Math.PI;
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/**
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* The three standard fingerprint ridge-flow patterns.
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*/
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public enum PatternType {WHORL, LOOP, ARCH}
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protected Fingerprint(BaseProviders faker) {
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super(faker);
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}
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/**
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* Returns raw PNG bytes of a random-pattern fingerprint image.
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*/
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public byte[] png() {
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return png(DEFAULT_WIDTH, DEFAULT_HEIGHT, randomType());
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}
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/**
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* Returns raw PNG bytes of a fingerprint image with the specified size and pattern.
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*/
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public byte[] png(int width, int height, PatternType pattern) {
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return encodePng(render(width, height, pattern));
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}
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/**
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* Returns a base64 PNG data URL of a random-pattern fingerprint.
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*/
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public String base64() {
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return base64(DEFAULT_WIDTH, DEFAULT_HEIGHT, randomType());
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}
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/**
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* Returns a base64 PNG data URL of a random-pattern fingerprint image with the specified size and pattern.
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*/
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public String base64(int width, int height, PatternType pattern) {
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byte[] png = png(width, height, pattern);
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return "data:image/png;base64," + Base64.getEncoder().encodeToString(png);
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}
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private PatternType randomType() {
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return faker.random().nextEnum(PatternType.class);
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}
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private byte[] encodePng(BufferedImage image) {
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try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
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ImageIO.write(image, "PNG", baos);
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return baos.toByteArray();
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} catch (IOException e) {
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throw new RuntimeException("Failed to encode fingerprint as PNG", e);
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}
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}
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private BufferedImage render(int width, int height, PatternType patternType) {
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BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_BYTE_GRAY);
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// Core position – slightly randomised around the centre
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double cx = width * (0.47 + faker.random().nextDouble(-0.04, 0.04));
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double cy = height * (0.47 + faker.random().nextDouble(-0.04, 0.04));
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// Ridge parameters
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double ridgePeriod = 11.0 + faker.random().nextDouble(-2.0, 3.0);
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double ridgeFraction = 0.42 + faker.random().nextDouble(-0.04, 0.06);
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// Pattern-specific parameters
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double spiralFactor = 0.5 + faker.random().nextDouble(0.0, 0.5);
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double loopAmplitude = height * (0.18 + faker.random().nextDouble(0.0, 0.10));
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double loopSigma = Math.min(width, height) * (0.28 + faker.random().nextDouble(0.0, 0.12));
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double archAmplitude = height * (0.12 + faker.random().nextDouble(0.0, 0.08));
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double archSigma = width * (0.30 + faker.random().nextDouble(0.0, 0.15));
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// Organic displacement noise: three sine-wave components
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int numNoise = 3;
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double[] noiseAmp = {3.2, 1.6, 0.7};
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double[] noiseFreq = {0.014, 0.032, 0.068};
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double[] phasesX = new double[numNoise];
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double[] phasesY = new double[numNoise];
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for (int i = 0; i < numNoise; i++) {
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phasesX[i] = faker.random().nextDouble(0.0, TWO_PI);
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phasesY[i] = faker.random().nextDouble(0.0, TWO_PI);
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}
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// Oval mask (fingerprints are oval)
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double maskA = width * 0.44;
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double maskB = height * 0.46;
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double fadeZone = 0.13; // fraction of mask radius used for edge fade
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// Ink tones
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int ridgeGray = faker.random().nextInt(25, 65);
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int valleyGray = faker.random().nextInt(195, 235);
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for (int y = 0; y < height; y++) {
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for (int x = 0; x < width; x++) {
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// Sine-wave displacement gives ridges an organic, non-straight look
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double noiseX = 0, noiseY = 0;
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for (int i = 0; i < numNoise; i++) {
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double f = noiseFreq[i];
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noiseX += noiseAmp[i] * Math.sin(x * f + y * f * 0.6 + phasesX[i]);
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noiseY += noiseAmp[i] * Math.sin(y * f + x * f * 0.6 + phasesY[i]);
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}
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double dx = x + noiseX - cx;
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double dy = y + noiseY - cy;
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double r = Math.sqrt(dx * dx + dy * dy);
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// Ridge value – periodic over ridgePeriod
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double ridgeVal = switch (patternType) {
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case WHORL -> {
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// Spiral: angle controls how much the ridges rotate
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double theta = Math.atan2(dy, dx); // −PI … PI
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yield r + spiralFactor * ridgePeriod * theta / Math.PI;
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}
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case LOOP -> {
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// Pull the effective centre upward near the core to form a loop
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double pull = loopAmplitude * Math.exp(-r * r / (2 * loopSigma * loopSigma));
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double loopDy = dy - pull;
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yield Math.sqrt(dx * dx + loopDy * loopDy);
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}
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case ARCH -> {
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// Ridges arch upward over the core
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double arch = archAmplitude * Math.exp(-dx * dx / (2 * archSigma * archSigma));
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yield dy + arch;
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}
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};
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double mod = ((ridgeVal % ridgePeriod) + ridgePeriod) % ridgePeriod;
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boolean isRidge = mod < ridgePeriod * ridgeFraction;
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// Oval mask with smooth edge fade toward white
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double mx = (x - width * 0.5) / maskA;
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double my = (y - height * 0.5) / maskB;
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double maskDist = mx * mx + my * my;
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int pixel;
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if (maskDist >= 1.0) {
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pixel = 255;
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} else {
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double fade = Math.min(1.0, (1.0 - maskDist) / fadeZone);
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int base = isRidge ? ridgeGray : valleyGray;
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pixel = (int) Math.round(base * fade + 255.0 * (1.0 - fade));
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}
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image.getRaster().setSample(x, y, 0, pixel);
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}
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}
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return image;
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}
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}

‎src/main/resources/META-INF/native-image/reachability-metadata.json‎

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"name": "financialTerms",
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"parameterTypes": []
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},
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{
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"name": "fingerprint",
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"parameterTypes": []
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},
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{
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"name": "funnyName",
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"parameterTypes": []
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}
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]
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},
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{
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"type": "net.datafaker.providers.base.Fingerprint",
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"methods": [
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{
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"name": "<init>",
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"parameterTypes": [
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"net.datafaker.providers.base.BaseProviders"
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]
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},
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{
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"name": "png",
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"parameterTypes": []
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},
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{
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"name": "png",
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"parameterTypes": [
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"int",
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"int",
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"net.datafaker.providers.base.Fingerprint$PatternType"
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]
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},
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{
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"name": "base64",
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"parameterTypes": []
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},
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{
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"name": "base64",
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"parameterTypes": [
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"int",
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"int",
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"net.datafaker.providers.base.Fingerprint$PatternType"
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]
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}
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]
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},
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{
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"type": "net.datafaker.providers.base.FunnyName",
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"methods": [

‎src/test/java/net/datafaker/providers/base/FingerprintTest.java‎

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package net.datafaker.providers.base;
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import net.datafaker.Faker;
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import org.junit.jupiter.api.Test;
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import org.junit.jupiter.params.ParameterizedTest;
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import org.junit.jupiter.params.provider.EnumSource;
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import javax.imageio.ImageIO;
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import java.awt.image.BufferedImage;
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import java.io.ByteArrayInputStream;
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import java.io.File;
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import java.io.IOException;
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import java.util.Base64;
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import static org.assertj.core.api.Assertions.assertThat;
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class FingerprintTest {
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private final Faker faker = new Faker();
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@Test
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void pngReturnsPngBytes() {
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byte[] bytes = faker.fingerprint().png();
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assertThat(bytes).isNotEmpty();
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// PNG magic: 0x89 P N G
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assertThat(bytes[0]).isEqualTo((byte) 0x89);
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assertThat(bytes[1]).isEqualTo((byte) 'P');
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assertThat(bytes[2]).isEqualTo((byte) 'N');
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assertThat(bytes[3]).isEqualTo((byte) 'G');
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}
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@Test
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void pngHasExpectedDimensions() throws IOException {
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byte[] bytes = faker.fingerprint().png();
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BufferedImage image = ImageIO.read(new ByteArrayInputStream(bytes));
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assertThat(image.getWidth()).isEqualTo(200);
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assertThat(image.getHeight()).isEqualTo(250);
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}
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@Test
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void base64ReturnsDataUrl() {
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String dataUrl = faker.fingerprint().base64();
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assertThat(dataUrl).startsWith("data:image/png;base64,");
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String encoded = dataUrl.substring("data:image/png;base64,".length());
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assertThat(encoded).isNotBlank().isBase64();
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}
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@Test
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void base64DecodesBackToPng() throws IOException {
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String dataUrl = faker.fingerprint().base64();
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String encoded = dataUrl.substring("data:image/png;base64,".length());
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byte[] bytes = Base64.getDecoder().decode(encoded);
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BufferedImage image = ImageIO.read(new ByteArrayInputStream(bytes));
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assertThat(image).isNotNull();
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assertThat(image.getWidth()).isEqualTo(200);
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assertThat(image.getHeight()).isEqualTo(250);
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}
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@ParameterizedTest
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@EnumSource(Fingerprint.PatternType.class)
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void eachPatternTypeProducesValidPng(Fingerprint.PatternType pattern) throws IOException {
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byte[] bytes = faker.fingerprint().png(400, 500, pattern);
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assertThat(bytes).isNotEmpty();
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assertThat(bytes[0]).isEqualTo((byte) 0x89);
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assertThat(bytes[1]).isEqualTo((byte) 'P');
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BufferedImage image = ImageIO.read(new ByteArrayInputStream(bytes));
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assertThat(image.getWidth()).isEqualTo(400);
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assertThat(image.getHeight()).isEqualTo(500);
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File folder = new File("target/surefire-reports");
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folder.mkdirs();
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ImageIO.write(image, "png", new File(folder, "fingerprint-" + pattern + ".png"));
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}
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@Test
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void twoPngCallsProduceDifferentImages() {
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byte[] first = faker.fingerprint().png();
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byte[] second = faker.fingerprint().png();
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// Extremely unlikely to be identical given randomised parameters
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assertThat(first).isNotEqualTo(second);
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}
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}

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