Fix a thin line of background showing on the right side (#50)

* Fix a thin line of background showing on the right side of contact sheets

If the contact sheet width (minus horizontal spacing) is not evenly divisible
by the number of image columns, a thin line of background is left visible on
the right side after composition.

Fix this by interpreting the value of --width as a target we try to match as
closely as possible, instead of as an unchangable constant.
In the current implementation this is an upper limit.

* Remove dead code

The grid is never set to None, so this check is useless

* Don't pass float dimensions to MediaInfo.desired_size

This should make the calculated frame height match the frame width more closely,
since the final rounding of the width is now preformed before it is used in the
calculation.

vcsi/vcsi.py

@@ -256,8 +256,8 @@ def desired_size(self, width=DEFAULT_CONTACT_SHEET_WIDTH):
         Returns (width, height)
         """
         ratio = width / float(self.display_width)
-        desired_height = math.floor(self.display_height * ratio)
-        return (int(width), int(desired_height))
+        desired_height = int(math.floor(self.display_height * ratio))
+        return (width, desired_height)
 
     def parse_attributes(self):
         """Parse multiple media attributes
@@ -501,10 +501,8 @@ def grid_desired_size(
     """Computes the size of the images placed on a mxn grid with given fixed width.
     Returns (width, height)
     """
-    if grid:
-        desired_width = (width - (grid.x - 1) * horizontal_margin) / grid.x
-    else:
-        desired_width = width
+    desired_width = (width - (grid.x - 1) * horizontal_margin) / grid.x
+    desired_width = int(math.floor(desired_width))
 
     return media_info.desired_size(width=desired_width)
 
@@ -797,6 +795,7 @@ def compose_contact_sheet(
         media_info,
         width=args.vcs_width,
         horizontal_margin=args.grid_horizontal_spacing)
+    width = args.grid.x * (desired_size[0] + args.grid_horizontal_spacing) - args.grid_horizontal_spacing
     height = args.grid.y * (desired_size[1] + args.grid_vertical_spacing) - args.grid_vertical_spacing
 
     try:
@@ -818,7 +817,7 @@ def compose_contact_sheet(
         media_info,
         header_font,
         args.metadata_horizontal_margin,
-        args.vcs_width,
+        width,
         template_path=args.metadata_template_path)
 
     line_spacing_coefficient = 1.2
@@ -828,7 +827,7 @@ def compose_contact_sheet(
     if args.metadata_position == "hidden":
         header_height = 0
 
-    final_image_width = args.vcs_width
+    final_image_width = width
     final_image_height = height + header_height
     transparent = (255, 255, 255, 0)