diff --git a/PhotoBrowser.xcodeproj/project.pbxproj b/PhotoBrowser.xcodeproj/project.pbxproj
index 0f41937..275fe8a 100644
--- a/PhotoBrowser.xcodeproj/project.pbxproj
+++ b/PhotoBrowser.xcodeproj/project.pbxproj
@@ -18,6 +18,7 @@
 		4A7E8F3E224A16A6005B54C8 /* ImageContainerView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4A7E8F3D224A16A6005B54C8 /* ImageContainerView.swift */; };
 		4A8A90962244C27D00A09C55 /* HighResolutionImageView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4A8A90952244C27D00A09C55 /* HighResolutionImageView.swift */; };
 		4A8EB7291CEF16020065EAB0 /* PBActionBarItem.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4A8EB7281CEF16020065EAB0 /* PBActionBarItem.swift */; };
+		4ABA2F1F22B8929600DB589C /* UIImage+Resize.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4ABA2F1E22B8929600DB589C /* UIImage+Resize.swift */; };
 		864F45E81E9F0A4900FF9215 /* Skitch.swift in Sources */ = {isa = PBXBuildFile; fileRef = 864F45E71E9F0A4900FF9215 /* Skitch.swift */; };
 		86AEF7301EDEC8A000034DBA /* SkitchView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 86AEF72F1EDEC8A000034DBA /* SkitchView.swift */; };
 		A18117E01E83B66900F8CE8E /* CustomPhotoBroswerManager.swift in Sources */ = {isa = PBXBuildFile; fileRef = A18117DF1E83B66900F8CE8E /* CustomPhotoBroswerManager.swift */; };
@@ -67,6 +68,7 @@
 		4A7E8F3D224A16A6005B54C8 /* ImageContainerView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ImageContainerView.swift; sourceTree = "<group>"; };
 		4A8A90952244C27D00A09C55 /* HighResolutionImageView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = HighResolutionImageView.swift; sourceTree = "<group>"; };
 		4A8EB7281CEF16020065EAB0 /* PBActionBarItem.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = PBActionBarItem.swift; sourceTree = "<group>"; };
+		4ABA2F1E22B8929600DB589C /* UIImage+Resize.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "UIImage+Resize.swift"; sourceTree = "<group>"; };
 		864F45E71E9F0A4900FF9215 /* Skitch.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Skitch.swift; sourceTree = "<group>"; };
 		86AEF72F1EDEC8A000034DBA /* SkitchView.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = SkitchView.swift; sourceTree = "<group>"; };
 		A18117DF1E83B66900F8CE8E /* CustomPhotoBroswerManager.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = CustomPhotoBroswerManager.swift; sourceTree = "<group>"; };
@@ -182,6 +184,7 @@
 				C4C79EA02057808200C92C0C /* UIView+Frame.swift */,
 				C4B64B622117E95300B29C5B /* UIViewController+Animation.swift */,
 				4A70A002225308A100DBD070 /* Kingfisher+CacheSerializer.swift */,
+				4ABA2F1E22B8929600DB589C /* UIImage+Resize.swift */,
 			);
 			path = Extensions;
 			sourceTree = "<group>";
@@ -456,6 +459,7 @@
 				4A8EB7291CEF16020065EAB0 /* PBActionBarItem.swift in Sources */,
 				C4B64B5D2117E90000B29C5B /* DismissAnimation.swift in Sources */,
 				C4B64B652117EA6300B29C5B /* PBConstant.swift in Sources */,
+				4ABA2F1F22B8929600DB589C /* UIImage+Resize.swift in Sources */,
 				A18117E01E83B66900F8CE8E /* CustomPhotoBroswerManager.swift in Sources */,
 				86AEF7301EDEC8A000034DBA /* SkitchView.swift in Sources */,
 			);
diff --git a/PhotoBrowser/Extensions/UIImage+Resize.swift b/PhotoBrowser/Extensions/UIImage+Resize.swift
new file mode 100644
index 0000000..9800d90
--- /dev/null
+++ b/PhotoBrowser/Extensions/UIImage+Resize.swift
@@ -0,0 +1,21 @@
+//
+//  UIImage+Resize.swift
+//  PhotoBrowser
+//
+//  Created by WangWei on 2019/6/18.
+//  Copyright © 2019 Teambition. All rights reserved.
+//
+
+import UIKit
+
+extension UIImage {
+    func resize(to size: CGSize) -> UIImage {
+        UIGraphicsBeginImageContextWithOptions(size, false, 0)
+        let context = UIGraphicsGetCurrentContext()
+        draw(in: CGRect(origin: .zero, size: size))
+        guard let cgImage = context?.makeImage() else {
+            return self
+        }
+        return UIImage(cgImage: cgImage)
+    }
+}
diff --git a/PhotoBrowser/PhotoPreview/PhotoPreviewController.swift b/PhotoBrowser/PhotoPreview/PhotoPreviewController.swift
index 7703ec3..761e2c5 100644
--- a/PhotoBrowser/PhotoPreview/PhotoPreviewController.swift
+++ b/PhotoBrowser/PhotoPreview/PhotoPreviewController.swift
@@ -203,7 +203,8 @@ extension PhotoPreviewController {
         let pointSize = miniMapSize
         DispatchQueue.global().async { [weak self] in
             // downsample image to minimap size to reduce memory cost
-            let downsampled = image.kf.resize(to: pointSize, for: .aspectFit)
+            let targetSize = image.size.kf.resize(to: pointSize, for: .aspectFit)
+            let downsampled = image.resize(to: targetSize)
             DispatchQueue.main.async {
                 self?.miniMap?.image = downsampled
             }