diff --git a/main.py b/main.py
index 1e99b0f..b9706ef 100644
--- a/main.py
+++ b/main.py
@@ -29,6 +29,7 @@ def convert_all(path = os.path.abspath('.')):
 def convert_img(path = os.path.abspath('.')):
     files = os.listdir(path)
     for file in files:
+        file = file.lower()             # 排除 .PNG 等带来的问题
         if file.endswith('.pdf'):
             result = pdf2img(path, file)
             if result:                  # 1 -> Error
@@ -52,7 +53,7 @@ def gen_filelist(path = os.path.abspath('.')):
         png_count = 0
         dir_file_copy = copy(dir_file)
         for file in dir_file_copy:
-            if ".png" in file:
+            if ".png" in file.lower():
                 png_count += 1
             else:
                 dir_file.remove(file)