SETUP move code to src

This way we can ensure that the packaged code is tested.
See https://hynek.me/articles/testing-packaging/ or c62a78c015

+ DOC adapt doc to new structure and test doc with travis

src/escpos/image.py

@@ -0,0 +1,90 @@
+""" Image format handling class
+
+This module contains the image format handler :py:class:`EscposImage`.
+
+:author: `Michael Billington <michael.billington@gmail.com>`_
+:organization: `python-escpos <https://github.com/python-escpos>`_
+:copyright: Copyright (c) 2016 Michael Billington <michael.billington@gmail.com>
+:license: GNU GPL v3
+"""
+
+from PIL import Image, ImageOps
+
+
+class EscposImage(object):
+    """
+    Load images in, and output ESC/POS formats.
+
+    The class is designed to efficiently delegate image processing to
+    PIL, rather than spend CPU cycles looping over pixels.
+    """
+
+    def __init__(self, img_source):
+        """
+        Load in an image
+        
+        :param img_source: PIL.Image, or filename to load one from.
+        """
+        if isinstance(img_source, Image.Image):
+            img_original = img_source
+        else:
+            img_original = Image.open(img_source)
+
+        # Convert to white RGB background, paste over white background
+        # to strip alpha.
+        img_original = img_original.convert('RGBA')
+        im = Image.new("RGB", img_original.size, (255, 255, 255))
+        im.paste(img_original, mask=img_original.split()[3])
+        # Convert down to greyscale
+        im = im.convert("L") 
+        # Invert: Only works on 'L' images
+        im = ImageOps.invert(im)
+        # Pure black and white
+        self._im = im.convert("1")
+    
+    @property
+    def width(self):
+        """
+        Width of image in pixels
+        """
+        width_pixels, _ = self._im.size
+        return width_pixels
+
+    @property
+    def width_bytes(self):
+        """
+        Width of image if you use 8 pixels per byte and 0-pad at the end.
+        """
+        return (self.width + 7) >> 3
+
+    @property
+    def height(self):
+        """
+        Height of image in pixels
+        """
+        _, height_pixels = self._im.size
+        return height_pixels
+
+    def to_column_format(self, high_density_vertical=True):
+        """
+        Extract slices of an image as equal-sized blobs of column-format data.
+
+        :param high_density_vertical: Printed line height in dots
+        """
+        im = self._im.transpose(Image.ROTATE_270).transpose(Image.FLIP_LEFT_RIGHT)
+        line_height = 24 if high_density_vertical else 8
+        width_pixels, height_pixels = im.size
+        top = 0
+        left = 0
+        while left < width_pixels:
+            box = (left, top, left + line_height, top + height_pixels)
+            im_slice = im.transform((line_height, height_pixels), Image.EXTENT, box)
+            im_bytes = im_slice.tobytes()
+            yield(im_bytes)
+            left += line_height
+
+    def to_raster_format(self):
+        """
+        Convert image to raster-format binary
+        """
+        return self._im.tobytes()