From dd7f04af44c4c5b8a042e1bc6d22b649429ecc24 Mon Sep 17 00:00:00 2001
From: Looly <loolly@gmail.com>
Date: Thu, 30 Jul 2020 10:06:42 +0800
Subject: [PATCH] fix img

---
 CHANGELOG.md                                       |  1 +
 .../src/main/java/cn/hutool/core/img/Img.java      | 14 +++++++++++---
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 979c540f3..dd87252ad 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@
 ### 新特性
 * 【captcha】     AbstractCaptcha增加getImageBase64Data方法（pr#985@Github）
 * 【core   】     增加PhoneUtil（pr#990@Github）
+* 【core   】     改进Img，目标图片类型未定义使用源图片类型（issue#I1PB0B@Gitee）
 
 ### Bug修复
 
diff --git a/hutool-core/src/main/java/cn/hutool/core/img/Img.java b/hutool-core/src/main/java/cn/hutool/core/img/Img.java
index f927cb92a..d16de3a45 100644
--- a/hutool-core/src/main/java/cn/hutool/core/img/Img.java
+++ b/hutool-core/src/main/java/cn/hutool/core/img/Img.java
@@ -134,7 +134,7 @@ public class Img implements Serializable {
 	}
 
 	/**
-	 * 构造
+	 * 构造，目标图片类型取决于来源图片类型
 	 *
 	 * @param srcImage 来源图片
 	 */
@@ -146,13 +146,21 @@ public class Img implements Serializable {
 	 * 构造
 	 *
 	 * @param srcImage        来源图片
-	 * @param targetImageType 目标图片类型
+	 * @param targetImageType 目标图片类型，null则读取来源图片类型
 	 * @since 5.0.7
 	 */
 	public Img(BufferedImage srcImage, String targetImageType) {
 		this.srcImage = srcImage;
 		if (null == targetImageType) {
-			targetImageType = ImgUtil.IMAGE_TYPE_JPG;
+			if (srcImage.getType() == BufferedImage.TYPE_INT_ARGB
+					|| srcImage.getType() == BufferedImage.TYPE_INT_ARGB_PRE
+					|| srcImage.getType() == BufferedImage.TYPE_4BYTE_ABGR
+					|| srcImage.getType() == BufferedImage.TYPE_4BYTE_ABGR_PRE
+			) {
+				targetImageType = ImgUtil.IMAGE_TYPE_PNG;
+			} else {
+				targetImageType = ImgUtil.IMAGE_TYPE_JPG;
+			}
 		}
 		this.targetImageType = targetImageType;
 	}