Include a pixels-to-rectangles example

examples/README.md

@@ -45,6 +45,7 @@ List of examples
 | [New layer](new_layer.py) | Add a layer to an image. |
 | [Overlapping circles](overlapping_circles.py) | Draw an array of hundreds of overlapping circles. |
 | [Path effects](path_effects.py) | Demonstrate the application of live path effects to a curve. |
+| [Pixels to rectangles](pixels_to_rectangles.py) | Show how to use the Python Imaging Library to convert each pixel of a bitmapped image to a colored rectangle. |
 | [Poly by angle](poly_by_angle.py) | Draw (possibly self-intersecting) polygons. |
 | [Screen vs print](screen_vs_print.py) | Create a printable page that is differently sized and disjoint from the main canvas. |
 | [Sierpinski triangle](sierpinski_triangle.py) | Draw a colorful Sierpinski triangle. |

examples/pixels_to_rectangles.py

@@ -0,0 +1,48 @@
+###########################################################
+# Show how to use the Python Imaging Library to convert   #
+# each pixel of a bitmapped image to a colored rectangle. #
+###########################################################
+
+import base64
+from PIL import Image
+import io
+
+
+def render_with_rectangles(obj):
+    'Render an image with SVG rectangles.'
+    # Convert the SVG image to an RGBA PIL image by parsing the raw data.
+    img_data_b64 = obj.svg_get('xlink:href', True).partition(',')[2]
+    img_data = base64.b64decode(img_data_b64)
+    img = Image.open(io.BytesIO(img_data)).convert(mode='RGBA')
+
+    # Acquire image properties.
+    pix_x0, pix_y0 = obj.svg_get('x'), obj.svg_get('y')
+    pix_wd = inkex.units.convert_unit(obj.svg_get('width'), 'px')
+    pix_ht = inkex.units.convert_unit(obj.svg_get('height'), 'px')
+    iwd, iht = img.width, img.height
+    xedge, yedge = pix_wd/iwd, pix_ht/iht
+    xform = obj.transform
+
+    # Convert each pixel to an SVG rectangle.
+    rectangles = []
+    for y in range(iht):
+        for x in range(iwd):
+            red, grn, blu, alp = img.getpixel((x, y))
+            x0, y0 = x*xedge + pix_x0, y*yedge + pix_y0
+            r = rect((x0, y0), (x0 + xedge, y0 + yedge),
+                     fill='#%02x%02x%02x' % (red, grn, blu),
+                     stroke='none',
+                     opacity=alp/255,
+                     transform=xform)
+            rectangles.append(r)
+    return rectangles
+
+
+# Download a bitmapped image from the web.
+img_src = 'https://upload.wikimedia.org/wikipedia/commons/thumb/c/c0/' + \
+          'Gnome-emblem-web.svg/48px-Gnome-emblem-web.svg.png'
+img = image(img_src, (20, 20), embed=True, transform='scale(2)')
+
+# Convert each pixel of the image to an SVG rectangle.
+group(render_with_rectangles(img))
+img.remove()