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tune GifCaptcha: decrease character spacing, add jitter, slower frame rate

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This commit is contained in:
hrj 2021-04-19 17:17:24 +05:30
parent 7ad164e3c2
commit d81cf17a08
1 changed files with 8 additions and 4 deletions
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12
src/main/java/lc/captchas/GifCaptcha.java
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@ -29,7 +29,7 @@ public class GifCaptcha implements ChallengeProvider {
final var graphics2D = img.createGraphics(); final var graphics2D = img.createGraphics();
final var frc = graphics2D.getFontRenderContext(); final var frc = graphics2D.getFontRenderContext();
final var advances = new LinkedList<Integer>(); final var advances = new LinkedList<Integer>();
final var spacing = font.getStringBounds(" ", frc).getWidth() / 2; final var spacing = font.getStringBounds(" ", frc).getWidth() / 3;
var currX = 0; var currX = 0;
for (int i = 0; i < text.length(); i++) { for (int i = 0; i < text.length(); i++) {
final var c = text.charAt(i); final var c = text.charAt(i);
@ -52,11 +52,15 @@ public class GifCaptcha implements ChallengeProvider {
return img; return img;
} }
private int jitter() {
return HelperFunctions.randomNumber(-2, +2);
}
private byte[] gifCaptcha(final String text) { private byte[] gifCaptcha(final String text) {
try { try {
final var byteArrayOutputStream = new ByteArrayOutputStream(); final var byteArrayOutputStream = new ByteArrayOutputStream();
final var output = new MemoryCacheImageOutputStream(byteArrayOutputStream); final var output = new MemoryCacheImageOutputStream(byteArrayOutputStream);
final var writer = new GifSequenceWriter(output, 1, 600, true); final var writer = new GifSequenceWriter(output, 1, 900, true);
final var advances = computeOffsets(text); final var advances = computeOffsets(text);
final var prevColor = Color.getHSBColor(0f, 0f, 0.1f); final var prevColor = Color.getHSBColor(0f, 0f, 0.1f);
IntStream.range(0, text.length()).forEach(i -> { IntStream.range(0, text.length()).forEach(i -> {
@ -64,9 +68,9 @@ public class GifCaptcha implements ChallengeProvider {
final var prevI = (i - 1 + text.length()) % text.length(); final var prevI = (i - 1 + text.length()) % text.length();
final var nextImage = makeImage((g) -> { final var nextImage = makeImage((g) -> {
g.setColor(prevColor); g.setColor(prevColor);
g.drawString(String.valueOf(text.charAt(prevI)), advances[prevI], 45); g.drawString(String.valueOf(text.charAt(prevI)), advances[prevI] + jitter(), 45 + jitter());
g.setColor(color); g.setColor(color);
g.drawString(String.valueOf(text.charAt(i)), advances[i], 45); g.drawString(String.valueOf(text.charAt(i)), advances[i] + jitter(), 45 + jitter());
}); });
try { try {
writer.writeToSequence(nextImage); writer.writeToSequence(nextImage);