Merge pull request #946 from synesthesiam/master

Added alpha support to novice

skimage/novice/_novice.py

@@ -1,6 +1,7 @@
 import os
 import imghdr
 from collections import namedtuple
+from io import BytesIO
 
 import numpy as np
 from skimage import io
@@ -10,6 +11,9 @@ from skimage.color import color_dict
 from skimage.io.util import file_or_url_context, is_url
 
 import six
+from six.moves.urllib_parse import urlparse
+from six.moves.urllib import request
+urlopen = request.urlopen
 
 # Convert colors from `skimage.color` to uint8 and allow access through
 # dict or a named tuple.
@@ -72,15 +76,18 @@ class Pixel(object):
         Vertical coordinate of this pixel (bottom = 0).
     rgb : tuple
         RGB tuple with red, green, and blue components (0-255)
+    alpha : int
+        Transparency component (0-255), 255 (opaque) by default
 
     """
-    def __init__(self, pic, array, x, y, rgb):
+    def __init__(self, pic, array, x, y, rgb, alpha=255):
         self._picture = pic
         self._x = x
         self._y = y
         self._red = self._validate(rgb[0])
         self._green = self._validate(rgb[1])
         self._blue = self._validate(rgb[2])
+        self._alpha = self._validate(alpha)
 
     @property
     def x(self):
@@ -122,6 +129,16 @@ class Pixel(object):
         self._blue = self._validate(value)
         self._setpixel()
 
+    @property
+    def alpha(self):
+        """The transparency component of the pixel (0-255)."""
+        return self._alpha
+
+    @alpha.setter
+    def alpha(self, value):
+        self._alpha = self._validate(value)
+        self._setpixel()
+
     @property
     def rgb(self):
         """The RGB color components of the pixel (3 values 0-255)."""
@@ -129,7 +146,25 @@ class Pixel(object):
 
     @rgb.setter
     def rgb(self, value):
-        self._red, self._green, self._blue = (self._validate(v) for v in value)
+        if len(value) == 4:
+            self.rgba = value
+        else:
+            self._red, self._green, self._blue \
+                = (self._validate(v) for v in value)
+            self._alpha = 255
+            self._setpixel()
+
+    @property
+    def rgba(self):
+        """The RGB color and transparency components of the pixel
+        (4 values 0-255).
+        """
+        return (self.red, self.green, self.blue, self.alpha)
+
+    @rgba.setter
+    def rgba(self, value):
+        self._red, self._green, self._blue, self._alpha \
+            = (self._validate(v) for v in value)
         self._setpixel()
 
     def _validate(self, value):
@@ -145,16 +180,17 @@ class Pixel(object):
         return value
 
     def _setpixel(self):
-        self._picture.xy_array[self._x, self._y] = self.rgb
+        # RGB + alpha
+        self._picture.xy_array[self._x, self._y] = self.rgba
         self._picture._array_modified()
 
     def __eq__(self, other):
         if isinstance(other, Pixel):
-            return self.rgb == other.rgb
+            return self.rgba == other.rgba
 
     def __repr__(self):
-        args = self.red, self.green, self.blue
-        return "Pixel(red={0}, green={1}, blue={2})".format(*args)
+        args = self.red, self.green, self.blue, self.alpha
+        return "Pixel(red={0}, green={1}, blue={2}, alpha={3})".format(*args)
 
 
 class Picture(object):
@@ -165,9 +201,9 @@ class Picture(object):
     path : str
         Path to an image file to load / URL of an image
     array : array
-        Raw RGB image data [0-255], with origin at top-left.
+        Raw RGB or RGBA image data [0-255], with origin at top-left.
     xy_array : array
-        Raw RGB image data [0-255], with origin at bottom-left.
+        Raw RGB or RGBA image data [0-255], with origin at bottom-left.
 
     Examples
     --------
@@ -218,13 +254,17 @@ class Picture(object):
                 path = os.path.abspath(path)
             self._path = path
             with file_or_url_context(path) as context:
-                self.array = io.imread(context)
+                self.array = img_as_ubyte(io.imread(context))
                 self._format = imghdr.what(context)
         elif array is not None:
             self.array = array
         elif xy_array is not None:
             self.xy_array = xy_array
 
+        # Force RGBA internally (use max alpha)
+        if self.array.shape[-1] == 3:
+            self.array = np.insert(self.array, 3, values=255, axis=2)
+
     @staticmethod
     def from_size(size, color='black'):
         """Return a Picture of the specified size and a uniform color.
@@ -234,13 +274,18 @@ class Picture(object):
         size : tuple
             Width and height of the picture in pixels.
         color : tuple or str
-            RGB tuple with the fill color for the picture [0-255] or a valid
-            key in `color_dict`.
+            RGB or RGBA tuple with the fill color for the picture [0-255] or
+            a valid key in `color_dict`.
         """
         if isinstance(color, six.string_types):
             color = color_dict[color]
-        rgb_size = tuple(size) + (3,)
+        rgb_size = tuple(size) + (len(color),)
         array = np.ones(rgb_size, dtype=np.uint8) * color
+
+        # Force RGBA internally (use max alpha)
+        if array.shape[-1] == 3:
+            array = np.insert(array, 3, values=255, axis=2)
+
         return Picture(array=array)
 
     @property
@@ -384,13 +429,31 @@ class Picture(object):
     def blue(self, value):
         self._set_channel(2, value)
 
+    @property
+    def alpha(self):
+        """The transparency component of the pixel (0-255)."""
+        return self._get_channel(3).ravel()
+
+    @alpha.setter
+    def alpha(self, value):
+        self._set_channel(3, value)
+
     @property
     def rgb(self):
         """The RGB color components of the pixel (3 values 0-255)."""
-        return self.xy_array
+        return self.xy_array[:, :, :3]
 
     @rgb.setter
     def rgb(self, value):
+        self.xy_array[:, :, :3] = value
+
+    @property
+    def rgba(self):
+        """The RGBA color components of the pixel (4 values 0-255)."""
+        return self.xy_array
+
+    @rgba.setter
+    def rgba(self, value):
         self.xy_array[:] = value
 
     def __iter__(self):

skimage/novice/tests/test_novice.py

@@ -13,8 +13,12 @@ IMAGE_PATH = os.path.join(data_dir, "chelsea.png")
 SMALL_IMAGE_PATH = os.path.join(data_dir, "block.png")
 
 
-def _array_2d_to_RGB(array):
-    return np.tile(array[:, :, np.newaxis], (1, 1, 3))
+def _array_2d_to_RGBA(array):
+    return np.tile(array[:, :, np.newaxis], (1, 1, 4))
+
+
+def _array_2d_to_RGBA(array):
+    return np.tile(array[:, :, np.newaxis], (1, 1, 4))
 
 
 def test_xy_to_array_origin():
@@ -82,6 +86,28 @@ def test_pixel_rgb():
     for i, channel in enumerate((pixel.red, pixel.green, pixel.blue)):
         assert_equal(channel, i + 3)
 
+    pixel.rgb = np.arange(4)
+    assert_equal(pixel.rgb, np.arange(3))
+
+
+def test_pixel_rgba():
+    pic = novice.Picture.from_size((3, 3), color=(10, 10, 10))
+    pixel = pic[0, 0]
+    pixel.rgba = np.arange(4)
+
+    assert_equal(pixel.rgba, np.arange(4))
+    for i, channel in enumerate((pixel.red, pixel.green, pixel.blue, pixel.alpha)):
+        assert_equal(channel, i)
+
+    pixel.red = 3
+    pixel.green = 4
+    pixel.blue = 5
+    pixel.alpha = 6
+    assert_equal(pixel.rgba, np.arange(4) + 3)
+
+    for i, channel in enumerate((pixel.red, pixel.green, pixel.blue, pixel.alpha)):
+        assert_equal(channel, i + 3)
+
 
 def test_pixel_rgb_float():
     pixel = novice.Picture.from_size((1, 1))[0, 0]
@@ -89,6 +115,12 @@ def test_pixel_rgb_float():
     assert_equal(pixel.rgb, (1, 1, 1))
 
 
+def test_pixel_rgba_float():
+    pixel = novice.Picture.from_size((1, 1))[0, 0]
+    pixel.rgba = (1.1, 1.1, 1.1, 1.1)
+    assert_equal(pixel.rgba, (1, 1, 1, 1))
+
+
 def test_modified_on_set():
     pic = novice.Picture(SMALL_IMAGE_PATH)
     pic[0, 0] = (1, 1, 1)
@@ -161,7 +193,7 @@ def test_indexing():
 
 
 def test_picture_slice():
-    array = _array_2d_to_RGB(np.arange(0, 10)[np.newaxis, :])
+    array = _array_2d_to_RGBA(np.arange(0, 10)[np.newaxis, :])
     pic = novice.Picture(array=array)
 
     x_slice = slice(3, 8)
@@ -171,7 +203,7 @@ def test_picture_slice():
 
 def test_move_slice():
     h, w = 3, 12
-    array = _array_2d_to_RGB(np.linspace(0, 255, h * w).reshape(h, w))
+    array = _array_2d_to_RGBA(np.linspace(0, 255, h * w).reshape(h, w))
     array = array.astype(np.uint8)
 
     pic = novice.Picture(array=array)
@@ -191,7 +223,7 @@ def test_move_slice():
 
 def test_negative_index():
     n = 10
-    array = _array_2d_to_RGB(np.arange(0, n)[np.newaxis, :])
+    array = _array_2d_to_RGBA(np.arange(0, n)[np.newaxis, :])
     # Test both x and y indices.
     pic = novice.Picture(array=array)
     assert pic[-1, 0] == pic[n - 1, 0]
@@ -201,7 +233,7 @@ def test_negative_index():
 
 def test_negative_slice():
     n = 10
-    array = _array_2d_to_RGB(np.arange(0, n)[np.newaxis, :])
+    array = _array_2d_to_RGBA(np.arange(0, n)[np.newaxis, :])
     # Test both x and y slices.
     pic = novice.Picture(array=array)
     assert pic[-3:, 0] == pic[n - 3:, 0]
@@ -211,7 +243,7 @@ def test_negative_slice():
 
 def test_getitem_with_step():
     h, w = 5, 5
-    array = _array_2d_to_RGB(np.linspace(0, 255, h * w).reshape(h, w))
+    array = _array_2d_to_RGBA(np.linspace(0, 255, h * w).reshape(h, w))
     pic = novice.Picture(array=array)
     sliced_pic = pic[::2, ::2]
     assert sliced_pic == novice.Picture(array=array[::2, ::2])
@@ -271,5 +303,11 @@ def test_pixel_blue_raises():
     pixel.blue = 256
 
 
+@raises(ValueError)
+def test_pixel_alpha_raises():
+    pixel = novice.Picture.from_size((1, 1))[0, 0]
+    pixel.alpha = 256
+
+
 if __name__ == '__main__':
     np.testing.run_module_suite()