diff --git a/README.md b/README.md
index 69b0ffd..e3fc194 100644
--- a/README.md
+++ b/README.md
@@ -12,16 +12,18 @@ Color values are specified using triplets of float values, like (128.5, 34.234,
 
 python-FloatImg requires a shared object file (.so) that is not yet officialy available from FloatImg.
 
-The file `floatimg/settings.py` contains the path to the .so file.
+The file `floatimg/settings.py` contains the path to the .so file and the encoding of path characters.
 
 ## Usage
 
-The FloatImg class encapsulate core and file functionnalities of FloatImg library. Import if from the main module:
-
 ```python
 import floatimg
 ```
 
+The FloatImg class encapsulate core and file functionnalities of FloatImg library. Instances are created with functions from the module.
+
+Colors are tuple of three elements `(r, g, b)`.
+
 ### Image creation
 
 `FloatImg` has two class methods to create an image.
@@ -47,60 +49,54 @@ new_img = img.clone()
 new_img = img.clone(True)
 ```
 
-### Image manipulation
-
-#### Clear image
-
-Reset all pixels to zero.
-
-```python
-img.clear()
-```
-
-#### Copy pixels to another image
-
-```python
-img.copy_data(another_img)
-```
-
-#### Set pixel value
-
-```python
-img.put(x, y, (r, g, b))
-```
-
-#### Get pixel value
+### Basic pixel manipulation
 
 ```python
+# Get pixel value
 color = (r, g, b) = img.get(x, y)
+
+# Set pixel value
+img.put(x, y, (r, g, b))
+
+# Reset all pixels to zero.
+img.clear()
+
+# Copy pixels to another image of the same format
+img.copy_data(another_img)
 ```
 
 ### File manipulation
 
-#### Dump image to file
+#### Raw dump files
 
 ```python
-img.dump("/tmp/image_dump")
+# Dump image to file
+img.dump(path)
+
+# Restore image data from a dump file
+img.load(path)
+
+# Create a new image from a dump file
+img = floatimg.create_from_dump(path)
+
+# Get dump metadata (TODO create a FileInfo named tuple)
+witdh, height, img_type = floatimg.fileinfos(path)
 ```
 
-#### Restore image data from a dump file
+#### External formats
 
 ```python
-img.load("/tmp/image_dump")
+# export supports the following extentions : .fimg, .png, .tiff, .pnm, .fits
+# save as png
+img.export("test.png")
+
+# create an image instance from png file
+img = floatimg.create_from_png("test.png")
+
+# load pixel data from png file in an existing instance. size and type have to be compatible
+img.load_png("test.png")
 ```
 
-#### Create a new image from a dump file
-
-```python
-img = floatimg.create_from_dump("/tmp/image_dump")
-```
-#### Get dump metadata
-
-TODO create a FileInfo named tuple.
-
-```python
-witdh, height, img_type = floatimg.fileinfos("/tmp/image_dump")
-```
 
 ## Operators
 
diff --git a/floatimg/__init__.py b/floatimg/__init__.py
index 5cd4dad..b765067 100644
--- a/floatimg/__init__.py
+++ b/floatimg/__init__.py
@@ -8,6 +8,7 @@ from floatimg.image import (
     create,
     create_rgb,
     create_from_dump,
+    create_from_png,
     fileinfos,
 )
 
diff --git a/floatimg/image.py b/floatimg/image.py
index 932fe5a..2c01099 100644
--- a/floatimg/image.py
+++ b/floatimg/image.py
@@ -1,6 +1,6 @@
 import ctypes as ct
 
-from floatimg.settings import LIB
+from floatimg.settings import LIB, PATH_ENCODING
 
 ############################################################################################################
 # type constants
@@ -163,6 +163,19 @@ c_fimg_maximum.argtypes = (
 )
 c_fimg_maximum.restype = ct.c_int
 
+# Files i/o
+c_fimg_export_picture = LIB.fimg_export_picture
+c_fimg_export_picture.argtypes = (ct.POINTER(C_FloatImg), ct.c_char_p)
+c_fimg_export_picture.restype = ct.c_int
+
+c_fimg_create_from_png = LIB.fimg_create_from_png
+c_fimg_create_from_png.argtypes = (ct.c_char_p, ct.POINTER(C_FloatImg))
+c_fimg_create_from_png.restype = ct.c_int
+
+c_fimg_load_from_png = LIB.fimg_load_from_png
+c_fimg_load_from_png.argtypes = (ct.c_char_p, ct.POINTER(C_FloatImg))
+c_fimg_load_from_png.restype = ct.c_int
+
 
 ############################################################################################################
 class FloatImg:
@@ -175,7 +188,7 @@ class FloatImg:
     """
 
     # proxy attributes to the C_FloatImg structure
-    # TODO: now more about them
+    # TODO: now more about them ;)
     magic = property(lambda self: self.c_img.magic)
     fval = property(lambda self: self.c_img.fval)
     count = property(lambda self: self.c_img.count)
@@ -247,22 +260,32 @@ class FloatImg:
         assert c_fimg_add_rgb(self.c_img_p, x, y, *color) == 0
 
     #######################################################################################################
-    def dump(self, fname):
+    def dump(self, path):
         """save data to a dump file"""
         # TODO use system encoding instead of utf-8
         assert (
             c_fimg_dump_to_file(
-                self.c_img_p, ct.c_char_p(bytes(fname, encoding="utf8")), 0
+                self.c_img_p, ct.c_char_p(bytes(path, encoding=PATH_ENCODING)), 0
             )
             == 0
         )
 
     #######################################################################################################
-    def load(self, fname):
+    def load(self, path):
         """load data from a dump. size and type have to be compatible"""
         assert (
             c_fimg_load_from_dump(
-                ct.c_char_p(bytes(fname, encoding="utf8")), self.c_img_p
+                ct.c_char_p(bytes(path, encoding=PATH_ENCODING)), self.c_img_p
+            )
+            == 0
+        )
+
+    #######################################################################################################
+    def load_png(self, path):
+        """load data from a png file. size and type have to be compatible"""
+        assert (
+            c_fimg_load_from_png(
+                ct.c_char_p(bytes(path, encoding=PATH_ENCODING)), self.c_img_p
             )
             == 0
         )
@@ -292,7 +315,7 @@ class FloatImg:
     def min(self, img):
         """return a new image with minimum pixel values per channel between current and parameter"""
         res = self.clone(False)
-        # C code invert comparison
+        # C code inverts comparison
         assert c_fimg_maximum(self.c_img_p, img.c_img_p, res.c_img_p) == 0
         return res
 
@@ -300,12 +323,19 @@ class FloatImg:
     def max(self, img):
         """return a new image with maximum pixel values per channel between current and parameter"""
         res = self.clone(False)
-        # C code invert comparison
+        # C code inverts comparison
         assert c_fimg_minimum(self.c_img_p, img.c_img_p, res.c_img_p) == 0
         return res
 
-    # TODO
-    # export(fname, flags) : depending file extension, save to the correct format
+    #######################################################################################################
+    def export(self, path):
+        """export image to path. allowed extension: .fimg, .png, .tiff, .pnm, .fits"""
+        assert (
+            c_fimg_export_picture(
+                self.c_img_p, ct.c_char_p(bytes(path, encoding=PATH_ENCODING)), 0
+            )
+            == 0
+        )
 
 
 ###########################################################################################################
@@ -313,7 +343,9 @@ def fileinfos(fname):
     """return witdh, height, img_type triplet read from a dump file"""
     datas = (ct.c_int * 3)()
     assert (
-        c_fimg_fileinfos(ct.c_char_p(bytes(fname, encoding="utf8")), ct.pointer(datas))
+        c_fimg_fileinfos(
+            ct.c_char_p(bytes(fname, encoding=PATH_ENCODING)), ct.pointer(datas)
+        )
         == 0
     )
     return datas[:3]
@@ -335,14 +367,25 @@ def create_rgb(witdh, height):
 
 
 ###########################################################################################################
-def create_from_dump(fname):
-    """Create a new instance from a dump file"""
-    witdh, height, img_type = fileinfos(fname)
+def create_from_dump(path):
+    """Create a FloatImg instance from a dump file"""
+    witdh, height, img_type = fileinfos(path)
     img = create(witdh, height, img_type)
-    img.load(fname)
+    img.load(path)
     return img
 
 
+###########################################################################################################
+def create_from_png(path):
+    """Create a FloatImg instance from a png file"""
+    img = C_FloatImg()
+    assert (
+        c_fimg_create_from_png(ct.c_char_p(bytes(path, encoding=PATH_ENCODING)), img)
+        == 0
+    )
+    return FloatImg(img)
+
+
 ###########################################################################################################
 def type_is_valid(type_id):
     """return True if type_id is a valid one"""
diff --git a/floatimg/settings.py b/floatimg/settings.py
index 8bd20f5..782d282 100644
--- a/floatimg/settings.py
+++ b/floatimg/settings.py
@@ -1,5 +1,5 @@
 import ctypes
 
-# LIB = ctypes.cdll.LoadLibrary("../FloatImg/libfloatimg.so")
+PATH_ENCODING = "utf8"
 
 LIB = ctypes.cdll.LoadLibrary("../FloatImg4PythonBinding/build/lib/libfloatimg.so")
diff --git a/tests/files.py b/tests/files.py
new file mode 100644
index 0000000..aa5c423
--- /dev/null
+++ b/tests/files.py
@@ -0,0 +1,28 @@
+import os
+
+import floatimg
+
+def create_img():
+    width, height = 5, 5
+    img = floatimg.create_rgb(width, height)
+    img.fill((255.0, 0.0, 0.0))
+    return img
+
+def test_png():
+    width, height = 5, 5
+    path = "test.png"
+    img = create_img()
+    img.export(path)
+    assert os.path.getsize(path) == 74
+    img2 = floatimg.create_from_png(path)
+    for y in range(height):
+        for x in range(width):
+            assert img.get(x, y) == img2.get(x, y)
+
+    img3 = img2.clone(False)
+    img3.load_png(path)
+    for y in range(height):
+        for x in range(width):
+            assert img.get(x, y) == img3.get(x, y)
+
+