Adjust SVG viewBox to enclose the font's bounding box (#23)

* Adjust Viewbox to contain whole letter

* Help typo fix

* ViewBox fallback to default values

* Use head table for Viewbox calc.

* Remove code duplicate: only return viewbox params

* Test -av option and viewbox param generation

* Head table can be reused in viewbox_settings

* Remove unnecessary test param

* Fix width, height calculation add tests

Co-authored-by: Dávid Godzsák <godzsakdavid�@gmail.com>
Co-authored-by: Dávid Godzsák <dg@shape.dk>

Author: 3 people

lib/opentypesvg/fonts2svg.py

@@ -126,20 +126,18 @@ def processFonts(font_paths_list, hex_colors_list, outputFolderPath, options):
     glyphNamesToSaveInNestedFolder = get_gnames_to_save_in_nested_folder(
         glyphNamesList)
 
-    # Gather the fonts' UPM. For simplicity, it's assumed that all fonts have
-    # the same UPM value. If fetching the UPM value fails, default to 1000.
-    try:
-        upm = ttLib.TTFont(font_paths_list[0])['head'].unitsPerEm
-    except KeyError:
-        upm = 1000
-
     nestedFolderPath = None
     filesSaved = 0
 
+    viewbox = viewbox_settings(
+        font_paths_list[0],
+        options.adjust_view_box_to_glyph
+    )
+
     # Generate the SVGs
     for gName in glyphNamesList:
         svgStr = (u"""<svg xmlns="http://www.w3.org/2000/svg" """
-                  u"""viewBox="0 -{} {} {}">\n""".format(upm, upm, upm))
+                  u"""viewBox="{}">\n""".format(viewbox))
 
         for index, gSet in enumerate(glyphSetsList):
             # Skip glyphs that don't exist in the current font,
@@ -193,6 +191,28 @@ def processFonts(font_paths_list, hex_colors_list, outputFolderPath, options):
     final_message(filesSaved)
 
 
+def viewbox_settings(font_path, adjust_view_box_to_glyph):
+    try:
+        head = ttLib.TTFont(font_path)["head"]
+        if adjust_view_box_to_glyph:
+            # it looks like compared to viewbox in the head table
+            # the yMin and yMax are inverted
+            x = head.xMin
+            y = -head.yMax
+            width = head.xMax - head.xMin
+            height = head.yMax - head.yMin
+            return """{} {} {} {}""".format(x, y, width, height)
+        else:
+            # Gather the fonts' UPM. For simplicity,
+            # it's assumed that all fonts have the same UPM value.
+            # If fetching the UPM value fails, default to 1000.
+            upm = head.unitsPerEm
+            return """0 -{} {} {}""".format(upm, upm, upm)
+    except KeyError:
+        upm = 1000
+        return """0 -{} {} {}""".format(upm, upm, upm)
+
+
 RE_HEXCOLOR = re.compile(r"^(?=[a-fA-F0-9]*$)(?:.{6}|.{8})$")
 
 
@@ -260,6 +280,12 @@ def get_options(args):
         dest='glyphsets_union',
         help="do union (instead of intersection) of the fonts' glyph sets."
     )
+    parser.add_argument(
+        '-av', '--adjust-viewbox',
+        action='store_true',
+        dest='adjust_view_box_to_glyph',
+        help="vertically center the viewBox on the bounding box of all glyphs."
+    )
     parser.add_argument(
         'input_paths',
         metavar='FONT',

tests/conftest.py

@@ -13,3 +13,8 @@ def fonts_dir():
 @pytest.fixture
 def base_font_path(fonts_dir):
     yield os.path.join(fonts_dir, 'Zebrawood.otf')
+
+
+@pytest.fixture
+def fixtures_dir():
+    yield os.path.join(os.path.dirname(__file__), 'fixtures')