diff --git a/README.md b/README.md
index 95119e8..751fec5 100644
--- a/README.md
+++ b/README.md
@@ -70,7 +70,7 @@ Example:
 ```py
 import pillowfight
 
-input_img = PIL.Image.open("tests/data/brightness_problem.jpg")
+input_img = PIL.Image.open("tests/data/brightness_problem.png")
 output_img = pillowfight.ace(input_img)
 ```
 
@@ -156,8 +156,8 @@ A basic documentation for some of the algorithms can be found in
 
 | Input | Output |
 | ----- | ------ |
-| [Black border problem](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem.jpg) | [ACE + Unpapered](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem_all.jpg) |
-| [Brightness problem](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/brightness_problem.jpg) | [ACE + Unpapered](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/brightness_problem_all.jpg) |
+| [Black border problem](tests/data/black_border_problem.png) | [ACE + Unpapered](tests/data/black_border_problem_all.png) |
+| [Brightness problem](tests/data/brightness_problem.png) | [ACE + Unpapered](tests/data/brightness_problem_all.png) |
 
 ## Available algorithms
 
@@ -165,7 +165,7 @@ A basic documentation for some of the algorithms can be found in
 
 | Input | Output |
 | ----- | ------ |
-| [Brightness problem](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/brightness_problem.jpg) | [Corrected](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/brightness_problem_ace.jpg) |
+| [Brightness problem](tests/data/brightness_problem.png) | [Corrected](tests/data/brightness_problem_ace.png) |
 
 This algorithm is quite slow (~40s for one big image with one thread
 on my machine). So this version is parallelized (down to ~15s on a 4
@@ -235,9 +235,9 @@ cropping area.
 
 | Input | Output |
 | ----- | ------ |
-| [brother_mfc7360n](https://gitlab.gnome.org/World/OpenPaperwork/libpillowfight/raw/master/tests/data/brother_mfc7360.jpeg) | (56, 8, 1637, 2275) |
-| [epson_xp425](https://gitlab.gnome.org/World/OpenPaperwork/libpillowfight/raw/master/tests/data/epson_xp425) | (4, 5, 2484, 3498) |
-| [brother_ds620](https://gitlab.gnome.org/World/OpenPaperwork/libpillowfight/raw/master/tests/data/brother_ds620.jpeg) | (3, 3, 2507, 3527) |
+| [brother_mfc7360n](tests/data/brother_mfc7360.png) | (56, 8, 1637, 2275) |
+| [epson_xp425](tests/data/epson_xp425.png) | (4, 5, 2484, 3498) |
+| [brother_ds620](tests/data/brother_ds620.png) | (3, 3, 2507, 3527) |
 
 #### Python API
 
@@ -272,7 +272,7 @@ struct pf_rectangle pf_find_scan_borders(const struct pf_bitmap *img_in);
 
 | Input | Output |
 | ----- | ------ |
-| [Crappy background](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/crappy_background.jpg) | [Canny output](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/crappy_background_canny.jpg) |
+| [Crappy background](tests/data/crappy_background.png) | [Canny output](tests/data/crappy_background_canny.png) |
 
 
 #### Python API
@@ -307,7 +307,7 @@ are considered equal).
 
 | Input | Input2 | Output |
 | ----- | ------ | ------ |
-| [Black border problem](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem.jpg) | [Black border problem + blackfilter](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem_blackfilter.jpg) | [Diff](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem_diff.jpg) |
+| [Black border problem](tests/data/black_border_problem.png) | [Black border problem + blackfilter](tests/data/black_border_problem_blackfilter.png) | [Diff](tests/data/black_border_problem_diff.png) |
 
 #### Python API
 
@@ -330,7 +330,7 @@ Returns the number of pixels that are different between both images.
 
 | Input | Output |
 | ----- | ------ |
-| [Crappy background](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/crappy_background.jpg) | [Gaussed](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/crappy_background_gaussian.jpg) |
+| [Crappy background](tests/data/crappy_background.png) | [Gaussed](tests/data/crappy_background_gaussian.png) |
 
 One of the parameters is ```sigma```. If it is equals to 0.0, it will be computed automatically
 using the following formula (same as OpenCV):
@@ -364,7 +364,7 @@ extern void pf_gaussian(const struct pf_bitmap *in, struct pf_bitmap *out,
 
 | Input | Output |
 | ----- | ------ |
-| [Crappy background](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/crappy_background.jpg) | [Sobel](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/crappy_background_sobel.jpg) |
+| [Crappy background](tests/data/crappy_background.png) | [Sobel](tests/data/crappy_background_sobel.png) |
 
 
 #### Python API
@@ -404,10 +404,10 @@ This implementation can provide the output in 3 different ways:
 
 | Input | Output |
 | ----- | ------ |
-| [Black border problen](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem.jpg) | [SWT (SWT_OUTPUT_ORIGINAL_BOXES)](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem_swt.jpg) |
-| [Crappy background](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/crappy_background.jpg) | [SWT (SWT_OUTPUT_ORIGINAL_BOXES)](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/crappy_background_swt.jpg) |
-| [Black border problen](https://raw.githubusercontent.com/openpaperwork/libpillowfight/47b1f59ce9a5fb3816e3abd186c28cc4c6092e13/tests/data/black_border_problem.jpg) | [SWT (SWT_OUTPUT_BW_TEXT)](https://raw.githubusercontent.com/openpaperwork/libpillowfight/47b1f59ce9a5fb3816e3abd186c28cc4c6092e13/tests/data/black_border_problem_swt.jpg) |
-| [Crappy background](https://raw.githubusercontent.com/openpaperwork/libpillowfight/47b1f59ce9a5fb3816e3abd186c28cc4c6092e13/tests/data/crappy_background.jpg) | [SWT (SWT_OUTPUT_BW_TEXT)](https://raw.githubusercontent.com/openpaperwork/libpillowfight/47b1f59ce9a5fb3816e3abd186c28cc4c6092e13/tests/data/crappy_background_swt.jpg) |
+| [Black border problen](tests/data/black_border_problem.png) | [SWT (SWT_OUTPUT_ORIGINAL_BOXES)](tests/data/black_border_problem_swt.png) |
+| [Crappy background](tests/data/crappy_background.png) | [SWT (SWT_OUTPUT_ORIGINAL_BOXES)](tests/data/crappy_background_swt.png) |
+| [Black border problen](tests/data/black_border_problem.png) | [SWT (SWT_OUTPUT_BW_TEXT)](tests/data/black_border_problem_swt.png) |
+| [Crappy background](tests/data/crappy_background.png) | [SWT (SWT_OUTPUT_BW_TEXT)](tests/data/crappy_background_swt.png) |
 
 
 #### Python API
@@ -447,7 +447,7 @@ extern void pf_swt(const struct pf_bitmap *in_img, struct pf_bitmap *out_img,
 
 | Input | Output | Diff |
 | ----- | ------ | ---- |
-| [Black border problem](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem.jpg) | [Filtered](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem_blackfilter.jpg) | [Diff](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem_blackfilter_diff.jpg) |
+| [Black border problem](tests/data/black_border_problem.png) | [Filtered](tests/data/black_border_problem_blackfilter.png) | [Diff](tests/data/black_border_problem_blackfilter_diff.png) |
 
 
 #### Python API
@@ -474,7 +474,7 @@ extern void pf_unpaper_blackfilter(const struct pf_bitmap *in, struct pf_bitmap
 
 | Input | Output | Diff |
 | ----- | ------ | ---- |
-| [Black border problem](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem.jpg) | [Filtered](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem_blurfilter.jpg) | [Diff](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem_blurfilter_diff.jpg) |
+| [Black border problem](tests/data/black_border_problem.png) | [Filtered](tests/data/black_border_problem_blurfilter.png) | [Diff](tests/data/black_border_problem_blurfilter_diff.png) |
 
 
 #### Python API
@@ -501,7 +501,7 @@ extern void pf_unpaper_blurfilter(const struct pf_bitmap *in, struct pf_bitmap *
 
 | Input | Output | Diff |
 | ----- | ------ | ---- |
-| [Black border problem 3](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem3.jpg) | [Border](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem3_border.jpg) | [Diff](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem3_border_diff.jpg) |
+| [Black border problem 3](tests/data/black_border_problem3.png) | [Border](tests/data/black_border_problem3_border.png) | [Diff](tests/data/black_border_problem3_border_diff.png) |
 
 
 #### Python API
@@ -528,7 +528,7 @@ extern void pf_unpaper_border(const struct pf_bitmap *in, struct pf_bitmap *out)
 
 | Input | Output | Diff |
 | ----- | ------ | ---- |
-| [Black border problem 3](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem.jpg) | [Filterd](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem_grayfilter.jpg) | [Diff](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem_grayfilter_diff.jpg) |
+| [Black border problem 3](tests/data/black_border_problem.png) | [Filterd](tests/data/black_border_problem_grayfilter.png) | [Diff](tests/data/black_border_problem_grayfilter_diff.png) |
 
 
 #### Python API
@@ -555,7 +555,7 @@ extern void pf_unpaper_grayfilter(const struct pf_bitmap *in, struct pf_bitmap *
 
 | Input | Output | Diff |
 | ----- | ------ | ---- |
-| [Black border problem 2](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem2.jpg) | [Masks](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem2_masks.jpg) | [Diff](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem2_masks_diff.jpg) |
+| [Black border problem 2](tests/data/black_border_problem2.png) | [Masks](tests/data/black_border_problem2_masks.png) | [Diff](tests/data/black_border_problem2_masks_diff.png) |
 
 
 #### Python API
@@ -582,7 +582,7 @@ extern void pf_unpaper_masks(const struct pf_bitmap *in, struct pf_bitmap *out);
 
 | Input | Output | Diff |
 | ----- | ------ | ---- |
-| [Black border problem](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem.jpg) | [Filtered](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem_noisefilter.jpg) | [Diff](https://raw.githubusercontent.com/openpaperwork/libpillowfight/master/tests/data/black_border_problem_noisefilter_diff.jpg) |
+| [Black border problem](tests/data/black_border_problem.png) | [Filtered](tests/data/black_border_problem_noisefilter.png) | [Diff](tests/data/black_border_problem_noisefilter_diff.png) |
 
 
 #### Python API
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diff --git a/tests/tests_ace.py b/tests/tests_ace.py
index 689e49b..76098b4 100644
--- a/tests/tests_ace.py
+++ b/tests/tests_ace.py
@@ -8,8 +8,8 @@
 
 class TestACE(unittest.TestCase):
     def test_ace(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/brightness_problem.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/brightness_problem.png")
             out_img = pillowfight.ace(in_img, seed=12345)
             in_img.close()
 
@@ -20,7 +20,7 @@ def test_ace(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/brightness_problem_ace.jpg"
+            "tests/data/brightness_problem_ace.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
diff --git a/tests/tests_all.py b/tests/tests_all.py
index 320f74d..0235848 100644
--- a/tests/tests_all.py
+++ b/tests/tests_all.py
@@ -8,8 +8,8 @@
 
 class TestAll(unittest.TestCase):
     def test_all_1(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/black_border_problem.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/black_border_problem.png")
 
             out_img = pillowfight.ace(in_img, seed=0xDEADBEE)
 
@@ -30,14 +30,14 @@ def test_all_1(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/black_border_problem_all.jpg"
+            "tests/data/black_border_problem_all.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
 
     def test_all_2(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/brightness_problem.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/brightness_problem.png")
 
             out_img = pillowfight.ace(in_img, seed=0xBEEDEAD)
 
@@ -58,7 +58,7 @@ def test_all_2(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/brightness_problem_all.jpg"
+            "tests/data/brightness_problem_all.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
diff --git a/tests/tests_blackfilter.py b/tests/tests_blackfilter.py
index 41d582c..20f018c 100644
--- a/tests/tests_blackfilter.py
+++ b/tests/tests_blackfilter.py
@@ -8,8 +8,8 @@
 
 class TestBlackfilter(unittest.TestCase):
     def test_blackfilter(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/black_border_problem.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/black_border_problem.png")
             out_img = pillowfight.unpaper_blackfilter(in_img)
             in_img.close()
 
@@ -20,7 +20,7 @@ def test_blackfilter(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/black_border_problem_blackfilter.jpg"
+            "tests/data/black_border_problem_blackfilter.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
diff --git a/tests/tests_blurfilter.py b/tests/tests_blurfilter.py
index 6d689f1..3ca7b99 100644
--- a/tests/tests_blurfilter.py
+++ b/tests/tests_blurfilter.py
@@ -8,8 +8,8 @@
 
 class TestBlurfilter(unittest.TestCase):
     def test_blurfilter(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/black_border_problem.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/black_border_problem.png")
             out_img = pillowfight.unpaper_blurfilter(in_img)
             in_img.close()
 
@@ -20,7 +20,7 @@ def test_blurfilter(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/black_border_problem_blurfilter.jpg"
+            "tests/data/black_border_problem_blurfilter.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
diff --git a/tests/tests_border.py b/tests/tests_border.py
index ecc36ec..aab573b 100644
--- a/tests/tests_border.py
+++ b/tests/tests_border.py
@@ -8,8 +8,8 @@
 
 class TestBorder(unittest.TestCase):
     def test_border(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/black_border_problem3.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/black_border_problem3.png")
             out_img = pillowfight.unpaper_border(in_img)
             in_img.close()
 
@@ -20,7 +20,7 @@ def test_border(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/black_border_problem3_border.jpg"
+            "tests/data/black_border_problem3_border.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
diff --git a/tests/tests_canny.py b/tests/tests_canny.py
index ba216b7..6882543 100644
--- a/tests/tests_canny.py
+++ b/tests/tests_canny.py
@@ -8,8 +8,8 @@
 
 class TestCanny(unittest.TestCase):
     def test_canny(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/crappy_background.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/crappy_background.png")
             out_img = pillowfight.canny(in_img)
             in_img.close()
 
@@ -20,7 +20,7 @@ def test_canny(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/crappy_background_canny.jpg"
+            "tests/data/crappy_background_canny.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
diff --git a/tests/tests_compare.py b/tests/tests_compare.py
index 385d3f0..9baf839 100644
--- a/tests/tests_compare.py
+++ b/tests/tests_compare.py
@@ -8,10 +8,10 @@
 
 class TestCompare(unittest.TestCase):
     def test_compare(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/black_border_problem.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/black_border_problem.png")
             in_img2 = PIL.Image.open(
-                "tests/data/black_border_problem_blackfilter.jpg"
+                "tests/data/black_border_problem_blackfilter.png"
             )
 
             (has_diff, out_img) = pillowfight.compare(in_img, in_img2)
@@ -26,7 +26,7 @@ def test_compare(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/black_border_problem_diff.jpg"
+            "tests/data/black_border_problem_diff.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
diff --git a/tests/tests_gaussian.py b/tests/tests_gaussian.py
index a56364c..68ac0e1 100644
--- a/tests/tests_gaussian.py
+++ b/tests/tests_gaussian.py
@@ -8,8 +8,8 @@
 
 class TestGaussian(unittest.TestCase):
     def test_gaussian(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/crappy_background.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/crappy_background.png")
             out_img = pillowfight.gaussian(in_img, sigma=20.0, nb_stddev=10)
             in_img.close()
 
@@ -20,7 +20,7 @@ def test_gaussian(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/crappy_background_gaussian.jpg"
+            "tests/data/crappy_background_gaussian.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
diff --git a/tests/tests_grayfilter.py b/tests/tests_grayfilter.py
index 20be0b2..7e7fc4d 100644
--- a/tests/tests_grayfilter.py
+++ b/tests/tests_grayfilter.py
@@ -8,8 +8,8 @@
 
 class TestGrayFilter(unittest.TestCase):
     def test_grayfilter(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/black_border_problem.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/black_border_problem.png")
             out_img = pillowfight.unpaper_grayfilter(in_img)
             in_img.close()
 
@@ -20,7 +20,7 @@ def test_grayfilter(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/black_border_problem_grayfilter.jpg"
+            "tests/data/black_border_problem_grayfilter.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
diff --git a/tests/tests_masks.py b/tests/tests_masks.py
index f67d36f..d941173 100644
--- a/tests/tests_masks.py
+++ b/tests/tests_masks.py
@@ -8,8 +8,8 @@
 
 class TestMasks(unittest.TestCase):
     def test_masks(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/black_border_problem2.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/black_border_problem2.png")
             out_img = pillowfight.unpaper_masks(in_img)
             in_img.close()
 
@@ -20,7 +20,7 @@ def test_masks(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/black_border_problem2_masks.jpg"
+            "tests/data/black_border_problem2_masks.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
diff --git a/tests/tests_noisefilter.py b/tests/tests_noisefilter.py
index 7d7936c..a84498b 100644
--- a/tests/tests_noisefilter.py
+++ b/tests/tests_noisefilter.py
@@ -8,8 +8,8 @@
 
 class TestNoisefilter(unittest.TestCase):
     def test_noisefilter(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/black_border_problem.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/black_border_problem.png")
             out_img = pillowfight.unpaper_noisefilter(in_img)
             in_img.close()
 
@@ -20,7 +20,7 @@ def test_noisefilter(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/black_border_problem_noisefilter.jpg"
+            "tests/data/black_border_problem_noisefilter.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
diff --git a/tests/tests_scan_borders.py b/tests/tests_scan_borders.py
index 474ef12..1953364 100644
--- a/tests/tests_scan_borders.py
+++ b/tests/tests_scan_borders.py
@@ -8,16 +8,16 @@
 
 class TestScanBorders(unittest.TestCase):
     def test_scan_borders_a(self):
-        in_img = PIL.Image.open("tests/data/brother_mfc7360.jpeg")
+        in_img = PIL.Image.open("tests/data/brother_mfc7360.png")
         frame = pillowfight.find_scan_borders(in_img)
         self.assertEqual(frame, (8, 37, 1637, 2195))
 
     def test_scan_borders_b(self):
-        in_img = PIL.Image.open("tests/data/epson_xp425.jpeg")
+        in_img = PIL.Image.open("tests/data/epson_xp425.png")
         frame = pillowfight.find_scan_borders(in_img)
         self.assertEqual(frame, (11, 4, 2541, 3503))
 
     def test_scan_borders_c(self):
-        in_img = PIL.Image.open("tests/data/brother_ds620.jpeg")
+        in_img = PIL.Image.open("tests/data/brother_ds620.png")
         frame = pillowfight.find_scan_borders(in_img)
         self.assertEqual(frame, (3, 3, 2507, 3527))
diff --git a/tests/tests_sobel.py b/tests/tests_sobel.py
index 6b74e88..ecff35b 100644
--- a/tests/tests_sobel.py
+++ b/tests/tests_sobel.py
@@ -8,8 +8,8 @@
 
 class TestSobel(unittest.TestCase):
     def test_sobel(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/crappy_background.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/crappy_background.png")
             out_img = pillowfight.sobel(in_img)
             in_img.close()
 
@@ -20,7 +20,7 @@ def test_sobel(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/crappy_background_sobel.jpg"
+            "tests/data/crappy_background_sobel.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
diff --git a/tests/tests_swt.py b/tests/tests_swt.py
index 142e81b..acb6a4e 100644
--- a/tests/tests_swt.py
+++ b/tests/tests_swt.py
@@ -8,8 +8,8 @@
 
 class TestSWT(unittest.TestCase):
     def test_swt(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/crappy_background.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/crappy_background.png")
             out_img = pillowfight.swt(
                 in_img, output_type=pillowfight.SWT_OUTPUT_ORIGINAL_BOXES
             )
@@ -22,14 +22,14 @@ def test_swt(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/crappy_background_swt.jpg"
+            "tests/data/crappy_background_swt.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
 
     def test_swt2(self):
-        with tempfile.NamedTemporaryFile(suffix='.jpg') as tmpfile:
-            in_img = PIL.Image.open("tests/data/black_border_problem.jpg")
+        with tempfile.NamedTemporaryFile(suffix='.png') as tmpfile:
+            in_img = PIL.Image.open("tests/data/black_border_problem.png")
             out_img = pillowfight.swt(
                 in_img, output_type=pillowfight.SWT_OUTPUT_ORIGINAL_BOXES
             )
@@ -42,7 +42,7 @@ def test_swt2(self):
             out_img = PIL.Image.open(tmpfile.name)
 
         expected_img = PIL.Image.open(
-            "tests/data/black_border_problem_swt.jpg"
+            "tests/data/black_border_problem_swt.png"
         )
         self.assertEqual(out_img.tobytes(), expected_img.tobytes())
         expected_img.close()
diff --git a/upd_diffs.sh b/upd_diffs.sh
index ad1a6ad..e4f8b63 100755
--- a/upd_diffs.sh
+++ b/upd_diffs.sh
@@ -1,9 +1,9 @@
 #!/bin/bash
 
 cd tests/data
-gm compare black_border_problem.jpg black_border_problem_blackfilter.jpg -file black_border_problem_blackfilter_diff.jpg
-gm compare black_border_problem.jpg black_border_problem_blurfilter.jpg -file black_border_problem_blurfilter_diff.jpg
-gm compare black_border_problem3.jpg black_border_problem3_border.jpg -file black_border_problem3_border_diff.jpg
-gm compare black_border_problem.jpg black_border_problem_grayfilter.jpg -file black_border_problem_grayfilter_diff.jpg
-gm compare black_border_problem2.jpg black_border_problem2_masks.jpg -file black_border_problem2_masks_diff.jpg
-gm compare black_border_problem.jpg black_border_problem_noisefilter.jpg -file black_border_problem_noisefilter_diff.jpg
+gm compare black_border_problem.png black_border_problem_blackfilter.png -file black_border_problem_blackfilter_diff.png
+gm compare black_border_problem.png black_border_problem_blurfilter.png -file black_border_problem_blurfilter_diff.png
+gm compare black_border_problem3.png black_border_problem3_border.png -file black_border_problem3_border_diff.png
+gm compare black_border_problem.png black_border_problem_grayfilter.png -file black_border_problem_grayfilter_diff.png
+gm compare black_border_problem2.png black_border_problem2_masks.png -file black_border_problem2_masks_diff.png
+gm compare black_border_problem.png black_border_problem_noisefilter.png -file black_border_problem_noisefilter_diff.png