diff --git a/aircv/__init__.py b/aircv/__init__.py
index e8e52ea..a88e065 100644
--- a/aircv/__init__.py
+++ b/aircv/__init__.py
@@ -125,8 +125,28 @@ def find_all_template(im_source, im_search, threshold=0.5, maxcnt=0, rgb=False,
             resbgr[i] = cv2.matchTemplate(i_bgr[i], s_bgr[i], method)
         res = resbgr[0]*weight[0] + resbgr[1]*weight[1] + resbgr[2]*weight[2]
     else:
-        s_gray = cv2.cvtColor(im_search, cv2.COLOR_BGR2GRAY)
-        i_gray = cv2.cvtColor(im_source, cv2.COLOR_BGR2GRAY)
+        channel = 1 if len(im_search.shape) == 2 else im_search.shape[2]
+        if channel == 1:
+            # if the image is gray, then keep it
+            s_gray = im_search
+        elif channel == 3:
+            # if it's colorful, then convert it to gray
+            s_gray = cv2.cvtColor(im_search, cv2.COLOR_BGR2GRAY)
+        elif channel == 4:
+            # if it's colorful with transparent channel, then convert it to gray
+            s_gray = cv2.cvtColor(im_search, cv2.COLOR_BGRA2GRAY)
+
+        channel = 1 if len(im_source.shape) == 2 else im_source.shape[2]
+        if channel == 1:
+            # if the image is gray, then keep it
+            i_gray = im_source
+        elif channel == 3:
+            # if it's colorful, then convert it to gray
+            i_gray = cv2.cvtColor(im_source, cv2.COLOR_BGR2GRAY)
+        elif channel == 4:
+            # if it's colorful with transparent channel, then convert it to gray
+            i_gray = cv2.cvtColor(im_source, cv2.COLOR_BGRA2GRAY)
+
         # 边界提取(来实现背景去除的功能)
         if bgremove:
             s_gray = cv2.Canny(s_gray, 100, 200)
diff --git a/tests/example.py b/tests/example.py
index efaf32a..78f1c05 100644
--- a/tests/example.py
+++ b/tests/example.py
@@ -7,29 +7,70 @@
 """
 sift
 """
+import cv2
+import numpy as np
 
 import aircv as ac
 
 def sift_test():
     t1 = ac.imread("testdata/1s.png")
     t2 = ac.imread("testdata/2s.png")
-    print ac.sift_count(t1), ac.sift_count(t2)
+    print(ac.sift_count(t1), ac.sift_count(t2))
 
     result = ac.find_sift(t1, t2, min_match_count=ac.sift_count(t1)*0.4) # after many tests, 0.4 may be best
     if result:
-        print 'Same'
+        print('Same')
     else:
-        print 'Not same'
+        print('Not same')
 
-def tmpl_test():
-    t1 = ac.imread("testdata/2s.png")
-    t2 = ac.imread("testdata/2t.png")
+def tmpl_test(imgsrc, imgtgt):
+    t1 = ac.imread(imgsrc)
+    t2 = ac.imread(imgtgt)
     import time
     start = time.time()
-    print ac.find_all_template(t1, t2)
-    print 'Time used:', time.time() - start
+    print(ac.find_all_template(t1, t2))
+    print('Time used:', time.time() - start)
+
+
+def add_alpha(imgsrc, imgtgt):
+    # a tool to generate 4 channel image
+    img = cv2.imread(imgsrc)
+
+    b_channel, g_channel, r_channel = cv2.split(img)
+
+    alpha_channel = np.ones(b_channel.shape, dtype=b_channel.dtype) * 255
+    # 最小值为0
+    alpha_channel[:, :int(b_channel.shape[1] / 2)] = 100
+
+    img_BGRA = cv2.merge((b_channel, g_channel, r_channel, alpha_channel))
+    cv2.imwrite(imgtgt, img_BGRA)
+
+
+def to_grayscale(imgsrc, imgtgt):
+    # a tool to generate grayscale image
+    img = cv2.imread(imgsrc)
+
+    channel = img.shape[2]
+    if channel == 1:
+        img_gray = imgsrc
+    elif channel == 3:
+        img_gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
+    elif channel == 4:
+        img_gray = cv2.cvtColor(img, cv2.COLOR_BGRA2GRAY)
+
+    cv2.imwrite(imgtgt, img_gray)
+
 
 if __name__ == '__main__':
-    sift_test()
-    tmpl_test()
+    # sift_test()
+
+    # add_alpha('testdata/2s.png','testdata/2s_trans.png')
+    # to_grayscale('testdata/2s.png','testdata/2s_gray.png')
+
+    tmpl_test("testdata/2s.png", "testdata/2t.png")
+    # test find template in 3 channel images
+    tmpl_test("testdata/2s_trans.png", "testdata/2t.png")
+    # test find template in 4 channel images
+    tmpl_test("testdata/2s_gray.png", "testdata/2t.png")
+    # test find template in 1 channel images
 
diff --git a/tests/testdata/2s_gray.png b/tests/testdata/2s_gray.png
new file mode 100644
index 0000000..1844003
Binary files /dev/null and b/tests/testdata/2s_gray.png differ
diff --git a/tests/testdata/2s_trans.png b/tests/testdata/2s_trans.png
new file mode 100644
index 0000000..7eb64a0
Binary files /dev/null and b/tests/testdata/2s_trans.png differ