增加图形验证码文字颜色与背景颜色色差设置

hutool-captcha/src/test/java/cn/hutool/captcha/CaptchaUtilTest.java

@@ -1,8 +1,18 @@
 package cn.hutool.captcha;
 
+import cn.hutool.captcha.generator.CodeGenerator;
+import cn.hutool.captcha.generator.MathGenerator;
+import cn.hutool.core.img.GraphicsUtil;
+import cn.hutool.core.img.ImgUtil;
+import cn.hutool.core.util.ObjectUtil;
+import cn.hutool.core.util.RandomUtil;
 import org.junit.Ignore;
 import org.junit.Test;
 
+import java.awt.*;
+import java.awt.image.BufferedImage;
+import java.util.concurrent.ThreadLocalRandom;
+
 public class CaptchaUtilTest {
 
 	@Test
@@ -12,4 +22,69 @@ public class CaptchaUtilTest {
 			CaptchaUtil.createShearCaptcha(320, 240);
 		}
 	}
+
+	@Test
+	@Ignore
+	public void drawStringColourfulTest() {
+		for(int i = 0; i < 10; i++) {
+			AbstractCaptcha lineCaptcha = new TestLineCaptcha(200, 100, 5, 10);
+			lineCaptcha.write("d:/captcha/line"+i+".png");
+		}
+	}
+
+	static class TestLineCaptcha extends AbstractCaptcha{
+
+		public TestLineCaptcha(int width, int height, int codeCount, int interfereCount) {
+			super(width, height, codeCount, interfereCount);
+		}
+
+		@Override
+		protected Image createImage(String code) {
+			// 图像buffer
+			final BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
+			final Graphics2D g = GraphicsUtil.createGraphics(image, ObjectUtil.defaultIfNull(this.background, Color.WHITE));
+
+			// 干扰线
+			drawInterfere(g);
+
+			// 字符串
+			drawString(g, code);
+
+			return image;
+		}
+
+		// ----------------------------------------------------------------------------------------------------- Private method start
+		/**
+		 * 绘制字符串
+		 *
+		 * @param g {@link Graphics}画笔
+		 * @param code 验证码
+		 */
+		private void drawString(Graphics2D g, String code) {
+			// 指定透明度
+			if (null != this.textAlpha) {
+				g.setComposite(this.textAlpha);
+			}
+			GraphicsUtil.drawStringColourful(g, code, this.font, this.width, this.height,Color.WHITE,200);
+		}
+
+		/**
+		 * 绘制干扰线
+		 *
+		 * @param g {@link Graphics2D}画笔
+		 */
+		private void drawInterfere(Graphics2D g) {
+			final ThreadLocalRandom random = RandomUtil.getRandom();
+			// 干扰线
+			for (int i = 0; i < this.interfereCount; i++) {
+				int xs = random.nextInt(width);
+				int ys = random.nextInt(height);
+				int xe = xs + random.nextInt(width / 3);
+				int ye = ys + random.nextInt(height / 3);
+				g.setColor(ImgUtil.randomColor(random));
+				g.drawLine(xs, ys, xe, ye);
+			}
+		}
+		// ----------------------------------------------------------------------------------------------------- Private method start
+	}
 }