Add Opaque background color to drawing

README.md

@@ -109,7 +109,7 @@ When drawing tasks, arckit will intelligently resize all of the grids such that
 
 ```python
 >>> task = vis.draw_task(train_set[0], width=10, height=6, label='Example')
->>> vis.output_drawing(grid, "images/arcshow_example.png") # svg/pdf/png
+>>> vis.output_drawing(task, "images/arcshow_example.png") # svg/pdf/png
 ```
 
 ![Example of arckit output](./images/arcsave_example.png)

arckit/vis.py

@@ -16,6 +16,8 @@
     '#FFFFFF'
         ]
 
+bg_color = '#EEEFF6' # White
+
 def draw_grid(grid, xmax=10, ymax=10, padding=.5, extra_bottom_padding=0.5, group=False, add_size=True, label='', bordercol='#111111ff'):
     """
     Draws a grid, 
@@ -65,6 +67,12 @@ def draw_grid(grid, xmax=10, ymax=10, padding=.5, extra_bottom_padding=0.5, grou
         drawing = drawsvg.Group()
     else:
         drawing = drawsvg.Drawing(xsize+padding, ysize+padding+extra_bottom_padding, origin=(-0.5*padding, -0.5*padding))
+        # Add background rectangle first
+        drawing.append(drawsvg.Rectangle(
+            -0.5*padding, -0.5*padding,                          # x, y position with extra padding
+            xsize+padding, ysize+padding+extra_bottom_padding,   # width, height with padding
+            fill=bg_color                                        # background color `bg_color`
+        ))
         drawing.set_pixel_scale(40)
     # drawing = drawsvg.Group()
     for j, row in enumerate(grid):
@@ -262,4 +270,4 @@ def output_drawing(d: drawsvg.Drawing, filename: str, context=None):
         import cairosvg
         cairosvg.svg2pdf(bytestring=buffer.getvalue(), write_to=filename)
     else:
-        raise ValueError(f'Unknown file extension for {filename}')
+        raise ValueError(f'Unknown file extension for {filename}')