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GifCaptcha: show letters at different offsets 

Signed-off-by: hrj <harshad.rj@gmail.com>
This commit is contained in:
hrj 2021-04-19 16:59:14 +05:30
parent d32d836475
commit 7ad164e3c2
1 changed files with 45 additions and 10 deletions
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55
src/main/java/lc/captchas/GifCaptcha.java
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@ -3,9 +3,13 @@ package lc.captchas;
import java.awt.Font;
import java.awt.RenderingHints;
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Map;
import java.util.function.Consumer;
import java.util.stream.IntStream;
import java.util.LinkedList;
import java.util.List;
import javax.imageio.stream.MemoryCacheImageOutputStream;
@ -16,16 +20,34 @@ import lc.misc.HelperFunctions;
import lc.misc.GifSequenceWriter;
public class GifCaptcha implements ChallengeProvider {
private final Font font = new Font("Arial", Font.ROMAN_BASELINE, 48);
private final int width = 250;
private final int height = 100;
private BufferedImage charToImg(final String text) {
final var img = new BufferedImage(250, 100, BufferedImage.TYPE_INT_RGB);
final var font = new Font("Bradley Hand", Font.ROMAN_BASELINE, 48);
private Integer[] computeOffsets(final String text) {
final var img = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
final var graphics2D = img.createGraphics();
final var frc = graphics2D.getFontRenderContext();
final var advances = new LinkedList<Integer>();
final var spacing = font.getStringBounds(" ", frc).getWidth() / 2;
var currX = 0;
for (int i = 0; i < text.length(); i++) {
final var c = text.charAt(i);
advances.add(currX);
currX += font.getStringBounds(String.valueOf(c), frc).getWidth();
currX += spacing;
};
graphics2D.dispose();
return advances.toArray(new Integer[]{});
}
private BufferedImage makeImage(final Consumer<Graphics2D> f) {
final var img = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
final var graphics2D = img.createGraphics();
graphics2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
graphics2D.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
graphics2D.setFont(font);
graphics2D.setColor(new Color((int) (Math.random() * 0x1000000)));
graphics2D.drawString(text, 45, 45);
f.accept(graphics2D);
graphics2D.dispose();
return img;
}
@ -34,11 +56,24 @@ public class GifCaptcha implements ChallengeProvider {
try {
final var byteArrayOutputStream = new ByteArrayOutputStream();
final var output = new MemoryCacheImageOutputStream(byteArrayOutputStream);
final var writer = new GifSequenceWriter(output, 1, 1000, true);
for (int i = 0; i < text.length(); i++) {
final var nextImage = charToImg(String.valueOf(text.charAt(i)));
writer.writeToSequence(nextImage);
}
final var writer = new GifSequenceWriter(output, 1, 600, true);
final var advances = computeOffsets(text);
final var prevColor = Color.getHSBColor(0f, 0f, 0.1f);
IntStream.range(0, text.length()).forEach(i -> {
final var color = Color.getHSBColor(HelperFunctions.randomNumber(0, 100)/100.0f, 0.6f, 1.0f);
final var prevI = (i - 1 + text.length()) % text.length();
final var nextImage = makeImage((g) -> {
g.setColor(prevColor);
g.drawString(String.valueOf(text.charAt(prevI)), advances[prevI], 45);
g.setColor(color);
g.drawString(String.valueOf(text.charAt(i)), advances[i], 45);
});
try {
writer.writeToSequence(nextImage);
} catch (final IOException e) {
e.printStackTrace();
}
});
writer.close();
output.close();
return byteArrayOutputStream.toByteArray();