add getbbox and getlength, with tests

Squashed commits:

[ec9ec31b] add tests for invalid anchor
(cherry picked from commit 9e50a6a47f79876ee56942152047f03fff03c49b)

[386a9170] fix lint and docs
(cherry picked from commit 2d0d5282fcfc3ee332a41e60b865ee766445cc3d)

[29f5d4c9] restore and document previous getsize behaviour
see discussion in issue 4789
(cherry picked from commit 9fbc94571ce0ed42fdd11e99f343a1613c9dc6d3)

[0ffd51a0] add getbbox and getlength, with tests
(cherry picked from commit c5f63737476a998c81e589e5819d21ca69bb7b46)

Tests/fonts/LICENSE.txt

@@ -9,6 +9,7 @@ ter-x20b.pcf, from http://terminus-font.sourceforge.net/
 
 All of the above fonts are published under the SIL Open Font License (OFL) v1.1 (http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=OFL), which allows you to copy, modify, and redistribute them if you need to.
 
+OpenSansCondensed-LightItalic.tt, from https://fonts.google.com/specimen/Open+Sans, under Apache License 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 
 10x20-ISO8859-1.pcf, from https://packages.ubuntu.com/xenial/xfonts-base
 

Tests/test_imagefont.py

@@ -41,6 +41,7 @@ class TestImageFont:
             "getters": (13, 16),
             "mask": (107, 13),
             "multiline-anchor": 6,
+            "getlength": (36, 27, 27, 33),
         },
         (">=2.7",): {
             "multiline": 6.2,
@@ -48,6 +49,7 @@ class TestImageFont:
             "getters": (12, 16),
             "mask": (108, 13),
             "multiline-anchor": 4,
+            "getlength": (36, 21, 24, 33),
         },
         "Default": {
             "multiline": 0.5,
@@ -55,6 +57,7 @@ class TestImageFont:
             "getters": (12, 16),
             "mask": (108, 13),
             "multiline-anchor": 4,
+            "getlength": (36, 24, 24, 33),
         },
     }
 
@@ -198,6 +201,34 @@ class TestImageFont:
             # Epsilon ~.5 fails with FreeType 2.7
             assert_image_similar(im, target_img, self.metrics["textsize"])
 
+    @pytest.mark.parametrize(
+        "text,mode,font,size,length_basic_index,length_raqm",
+        (
+            # basic test
+            ("text", "L", "FreeMono.ttf", 15, 0, 36),
+            ("text", "1", "FreeMono.ttf", 15, 0, 36),
+            # issue 4177
+            ("rrr", "L", "DejaVuSans.ttf", 18, 1, 22.21875),
+            ("rrr", "1", "DejaVuSans.ttf", 18, 2, 22.21875),
+            # test 'l' not including extra margin
+            # using exact value 2047 / 64 for raqm, checked with debugger
+            ("ill", "L", "OpenSansCondensed-LightItalic.ttf", 63, 3, 31.984375),
+            ("ill", "1", "OpenSansCondensed-LightItalic.ttf", 63, 3, 31.984375),
+        ),
+    )
+    def test_getlength(self, text, mode, font, size, length_basic_index, length_raqm):
+        f = ImageFont.truetype(
+            "Tests/fonts/" + font, size, layout_engine=self.LAYOUT_ENGINE
+        )
+
+        if self.LAYOUT_ENGINE == ImageFont.LAYOUT_BASIC:
+            length = f.getlength(text, mode)
+            assert length == self.metrics["getlength"][length_basic_index]
+        else:
+            # disable kerning, kerning metrics changed
+            length = f.getlength(text, mode, features=["-kern"])
+            assert length == length_raqm
+
     def test_render_multiline(self):
         im = Image.new(mode="RGB", size=(300, 100))
         draw = ImageDraw.Draw(im)
@@ -754,27 +785,42 @@ class TestImageFont:
         self._check_text(font, "Tests/images/variation_tiny_axes.png", 32.5)
 
     @pytest.mark.parametrize(
-        "anchor",
+        "anchor,left,left_old,top",
         (
             # test horizontal anchors
-            "ls",
+            ("ls", 0, 0, -36),
-            "ms",
+            ("ms", -64, -65, -36),
-            "rs",
+            ("rs", -128, -129, -36),
             # test vertical anchors
-            "ma",
+            ("ma", -64, -65, 16),
-            "mt",
+            ("mt", -64, -65, 0),
-            "mm",
+            ("mm", -64, -65, -17),
-            "mb",
+            ("mb", -64, -65, -44),
-            "md",
+            ("md", -64, -65, -51),
         ),
+        ids=("ls", "ms", "rs", "ma", "mt", "mm", "mb", "md"),
     )
-    def test_anchor(self, anchor):
+    def test_anchor(self, anchor, left, left_old, top):
         name, text = "quick", "Quick"
         path = f"Tests/images/test_anchor_{name}_{anchor}.png"
+
+        freetype = parse_version(features.version_module("freetype2"))
+        if freetype < parse_version("2.4"):
+            width, height = (129, 44)
+            left = left_old
+        elif self.LAYOUT_ENGINE == ImageFont.LAYOUT_RAQM:
+            width, height = (129, 44)
+        else:
+            width, height = (128, 44)
+
         f = ImageFont.truetype(
             "Tests/fonts/NotoSans-Regular.ttf", 48, layout_engine=self.LAYOUT_ENGINE
         )
 
+        # test getbbox
+        assert f.getbbox(text, anchor=anchor) == (left, top, left + width, top + height)
+
+        # test render
         im = Image.new("RGB", (200, 200), "white")
         d = ImageDraw.Draw(im)
         d.line(((0, 100), (200, 100)), "gray")
@@ -831,6 +877,7 @@ class TestImageFont:
 
         for anchor in ["", "l", "a", "lax", "sa", "xa", "lx"]:
             pytest.raises(ValueError, lambda: font.getmask2("hello", anchor=anchor))
+            pytest.raises(ValueError, lambda: font.getbbox("hello", anchor=anchor))
             pytest.raises(ValueError, lambda: d.text((0, 0), "hello", anchor=anchor))
             pytest.raises(
                 ValueError, lambda: d.multiline_text((0, 0), "foo\nbar", anchor=anchor)

Tests/test_imagefontctl.py

@@ -209,6 +209,57 @@ def test_language():
         assert_image_similar(im, target_img, 0.5)
 
 
+@pytest.mark.parametrize("mode", ("L", "1"))
+@pytest.mark.parametrize(
+    "text,direction,expected",
+    (
+        ("سلطنة عمان Oman", None, 173.703125),
+        ("سلطنة عمان Oman", "ltr", 173.703125),
+        ("Oman سلطنة عمان", "rtl", 173.703125),
+        ("English عربي", "rtl", 123.796875),
+        ("test", "ttb", 80.0),
+    ),
+    ids=("None", "ltr", "rtl2", "rtl", "ttb"),
+)
+def test_getlength(mode, text, direction, expected):
+    try:
+        ttf = ImageFont.truetype(FONT_PATH, FONT_SIZE)
+
+        assert ttf.getlength(text, mode, direction) == expected
+    except ValueError as ex:
+        if (
+            direction == "ttb"
+            and str(ex) == "libraqm 0.7 or greater required for 'ttb' direction"
+        ):
+            pytest.skip("libraqm 0.7 or greater not available")
+
+
+@pytest.mark.parametrize("mode", ("L", "1"))
+@pytest.mark.parametrize("direction", ("ltr", "ttb"))
+@pytest.mark.parametrize(
+    "text",
+    ("i" + ("\u030C" * 15) + "i", "i" + "\u032C" * 15 + "i", "\u035Cii", "i\u0305i"),
+    ids=("caron-above", "caron-below", "double-breve", "overline"),
+)
+def test_getlength_combine(mode, direction, text):
+    if text == "i\u0305i" and direction == "ttb":
+        pytest.skip("fails with this font")
+
+    ttf = ImageFont.truetype("Tests/fonts/NotoSans-Regular.ttf", 48)
+
+    try:
+        target = ttf.getlength("ii", mode, direction)
+        actual = ttf.getlength(text, mode, direction)
+
+        assert actual == target
+    except ValueError as ex:
+        if (
+            direction == "ttb"
+            and str(ex) == "libraqm 0.7 or greater required for 'ttb' direction"
+        ):
+            pytest.skip("libraqm 0.7 or greater not available")
+
+
 @pytest.mark.parametrize("anchor", ("lt", "mm", "rb", "sm"))
 def test_anchor_ttb(anchor):
     if parse_version(features.version_module("freetype2")) < parse_version("2.5.1"):
@@ -298,6 +349,37 @@ def test_combine(name, text, dir, anchor, epsilon):
         assert_image_similar(im, expected, epsilon)
 
 
+@pytest.mark.parametrize(
+    "anchor,align",
+    (
+        ("lm", "left"),  # pass with getsize
+        ("lm", "center"),  # fail at 2.12
+        ("lm", "right"),  # fail at 2.57
+        ("mm", "left"),  # fail at 2.12
+        ("mm", "center"),  # pass with getsize
+        ("mm", "right"),  # fail at 2.12
+        ("rm", "left"),  # fail at 2.57
+        ("rm", "center"),  # fail at 2.12
+        ("rm", "right"),  # pass with getsize
+    ),
+)
+def test_combine_multiline(anchor, align):
+    # test that multiline text uses getlength, not getsize or getbbox
+
+    path = f"Tests/images/test_combine_multiline_{anchor}_{align}.png"
+    f = ImageFont.truetype("Tests/fonts/NotoSans-Regular.ttf", 48)
+    text = "i\u0305\u035C\ntext"  # i with overline and double breve, and a word
+
+    im = Image.new("RGB", (400, 400), "white")
+    d = ImageDraw.Draw(im)
+    d.line(((0, 200), (400, 200)), "gray")
+    d.line(((200, 0), (200, 400)), "gray")
+    d.multiline_text((200, 200), text, fill="black", anchor=anchor, font=f, align=align)
+
+    with Image.open(path) as expected:
+        assert_image_similar(im, expected, 0.015)
+
+
 def test_anchor_invalid_ttb():
     font = ImageFont.truetype(FONT_PATH, FONT_SIZE)
     im = Image.new("RGB", (100, 100), "white")
@@ -308,6 +390,9 @@ def test_anchor_invalid_ttb():
         pytest.raises(
             ValueError, lambda: font.getmask2("hello", anchor=anchor, direction="ttb")
         )
+        pytest.raises(
+            ValueError, lambda: font.getbbox("hello", anchor=anchor, direction="ttb")
+        )
         pytest.raises(
             ValueError, lambda: d.text((0, 0), "hello", anchor=anchor, direction="ttb")
         )

docs/reference/ImageDraw.rst

@@ -403,6 +403,15 @@ Methods
 
     Return the size of the given string, in pixels.
 
+    You can use :meth:`.FreeTypeFont.getlength` to measure text length
+    with 1/64 pixel precision.
+
+    .. note:: For historical reasons this function measures text height from
+        the ascender line instead of the top, see :ref:`text-anchors`.
+        If you wish to measure text height from the top, it is recommended
+        to use :meth:`.FreeTypeFont.getbbox` with ``anchor='lt'`` instead.
+
+
     :param text: Text to be measured. If it contains any newline characters,
                  the text is passed on to :py:meth:`~PIL.ImageDraw.ImageDraw.multiline_textsize`.
     :param font: An :py:class:`~PIL.ImageFont.ImageFont` instance.

src/PIL/ImageDraw.py

@@ -385,6 +385,9 @@ class ImageDraw:
         elif anchor[1] in "tb":
             raise ValueError("anchor not supported for multiline text")
 
+        if font is None:
+            font = self.getfont()
+
         widths = []
         max_width = 0
         lines = self._multiline_split(text)
@@ -392,13 +395,12 @@ class ImageDraw:
             self.textsize("A", font=font, stroke_width=stroke_width)[1] + spacing
         )
         for line in lines:
-            line_width, line_height = self.textsize(
+            line_width = font.getlength(
                 line,
-                font,
+                self.fontmode,
                 direction=direction,
                 features=features,
                 language=language,
-                stroke_width=stroke_width,
             )
             widths.append(line_width)
             max_width = max(max_width, line_width)

src/PIL/ImageFont.py

@@ -215,6 +215,140 @@ class FreeTypeFont:
         """
         return self.font.ascent, self.font.descent
 
+    def getlength(self, text, mode="", direction=None, features=None, language=None):
+        """
+        Returns length (in pixels with 1/64 precision) of given text if rendered
+        in font with provided direction, features, and language.
+
+        This is the amount by which following text should be offset.
+        Text bounding box may extend past the length in some fonts,
+        e.g. when using italics or accents.
+
+        The result is returned as a float; it is a whole number if using basic layout.
+
+        Note that the sum of two lengths may not equal the length of a concatenated
+        string due to kerning. If you need to adjust for kerning, include the following
+        character and subtract its length.
+
+        For example, instead of
+
+        .. code-block:: python
+
+          hello = font.getlength("Hello")
+          world = font.getlength("World")
+          hello_world = hello + world  # not adjusted for kerning
+          assert hello_world == font.getlength("HelloWorld")  # may fail
+
+        use
+
+        .. code-block:: python
+
+          hello = font.getlength("HelloW") - font.getlength("W")  # adjusted for kerning
+          world = font.getlength("World")
+          hello_world = hello + world  # adjusted for kerning
+          assert hello_world == font.getlength("HelloWorld")  # True
+
+        .. versionadded:: 8.0.0
+
+        :param text: Text to measure.
+        :param mode: Used by some graphics drivers to indicate what mode the
+                     driver prefers; if empty, the renderer may return either
+                     mode. Note that the mode is always a string, to simplify
+                     C-level implementations.
+
+        :param direction: Direction of the text. It can be 'rtl' (right to
+                          left), 'ltr' (left to right) or 'ttb' (top to bottom).
+                          Requires libraqm.
+
+        :param features: A list of OpenType font features to be used during text
+                         layout. This is usually used to turn on optional
+                         font features that are not enabled by default,
+                         for example 'dlig' or 'ss01', but can be also
+                         used to turn off default font features for
+                         example '-liga' to disable ligatures or '-kern'
+                         to disable kerning.  To get all supported
+                         features, see
+                         https://docs.microsoft.com/en-us/typography/opentype/spec/featurelist
+                         Requires libraqm.
+
+        :param language: Language of the text. Different languages may use
+                         different glyph shapes or ligatures. This parameter tells
+                         the font which language the text is in, and to apply the
+                         correct substitutions as appropriate, if available.
+                         It should be a `BCP 47 language code
+                         <https://www.w3.org/International/articles/language-tags/>`
+                         Requires libraqm.
+
+        :return: Width for horizontal, height for vertical text.
+        """
+        return (
+            self.font.getlength(text, mode == "1", direction, features, language) / 64
+        )
+
+    def getbbox(
+        self,
+        text,
+        mode="",
+        direction=None,
+        features=None,
+        language=None,
+        stroke_width=0,
+        anchor=None,
+    ):
+        """
+        Returns bounding box (in pixels) of given text relative to given anchor
+        if rendered in font with provided direction, features, and language.
+
+        Use :py:meth`getlength()` to get the offset of following text with
+        1/64 pixel precision. The bounding box includes extra margins for
+        some fonts, e.g. italics or accents.
+
+        .. versionadded:: 8.0.0
+
+        :param text: Text to render.
+        :param mode: Used by some graphics drivers to indicate what mode the
+                     driver prefers; if empty, the renderer may return either
+                     mode. Note that the mode is always a string, to simplify
+                     C-level implementations.
+
+        :param direction: Direction of the text. It can be 'rtl' (right to
+                          left), 'ltr' (left to right) or 'ttb' (top to bottom).
+                          Requires libraqm.
+
+        :param features: A list of OpenType font features to be used during text
+                         layout. This is usually used to turn on optional
+                         font features that are not enabled by default,
+                         for example 'dlig' or 'ss01', but can be also
+                         used to turn off default font features for
+                         example '-liga' to disable ligatures or '-kern'
+                         to disable kerning.  To get all supported
+                         features, see
+                         https://docs.microsoft.com/en-us/typography/opentype/spec/featurelist
+                         Requires libraqm.
+
+        :param language: Language of the text. Different languages may use
+                         different glyph shapes or ligatures. This parameter tells
+                         the font which language the text is in, and to apply the
+                         correct substitutions as appropriate, if available.
+                         It should be a `BCP 47 language code
+                         <https://www.w3.org/International/articles/language-tags/>`
+                         Requires libraqm.
+
+        :param stroke_width: The width of the text stroke.
+
+        :param anchor:  The text anchor alignment. Determines the relative location of
+                        the anchor to the text. The default alignment is top left.
+                        See :ref:`text-anchors` for valid values.
+
+        :return: ``(left, top, right, bottom)`` bounding box
+        """
+        size, offset = self.font.getsize(
+            text, mode == "1", direction, features, language, anchor
+        )
+        left, top = offset[0] - stroke_width, offset[1] - stroke_width
+        width, height = size[0] + 2 * stroke_width, size[1] + 2 * stroke_width
+        return left, top, left + width, top + height
+
     def getsize(
         self, text, direction=None, features=None, language=None, stroke_width=0
     ):
@@ -222,6 +356,15 @@ class FreeTypeFont:
         Returns width and height (in pixels) of given text if rendered in font with
         provided direction, features, and language.
 
+        Use :py:meth:`getlength()` to measure the offset of following text with
+        1/64 pixel precision.
+        Use :py:meth:`getbbox()` to get the exact bounding box based on an anchor.
+
+        .. note:: For historical reasons this function measures text height from
+            the ascender line instead of the top, see :ref:`text-anchors`.
+            If you wish to measure text height from the top, it is recommended
+            to use the bottom value of :meth:`getbbox` with ``anchor='lt'`` instead.
+
         :param text: Text to measure.
 
         :param direction: Direction of the text. It can be 'rtl' (right to

src/_imagingft.c

@@ -607,6 +607,49 @@ text_layout(PyObject* string, FontObject* self, const char* dir, PyObject *featu
     return count;
 }
 
+static PyObject*
+font_getlength(FontObject* self, PyObject* args)
+{
+    int length; /* length along primary axis, in 26.6 precision */
+    GlyphInfo *glyph_info = NULL; /* computed text layout */
+    size_t i, count; /* glyph_info index and length */
+    int horizontal_dir; /* is primary axis horizontal? */
+    int mask = 0; /* is FT_LOAD_TARGET_MONO enabled? */
+    const char *dir = NULL;
+    const char *lang = NULL;
+    PyObject *features = Py_None;
+    PyObject *string;
+
+    /* calculate size and bearing for a given string */
+
+    if (!PyArg_ParseTuple(args, "O|izOz:getlength", &string, &mask, &dir, &features, &lang)) {
+        return NULL;
+    }
+
+    horizontal_dir = dir && strcmp(dir, "ttb") == 0 ? 0 : 1;
+
+    count = text_layout(string, self, dir, features, lang, &glyph_info, mask);
+    if (PyErr_Occurred()) {
+        return NULL;
+    }
+
+    length = 0;
+    for (i = 0; i < count; i++) {
+        if (horizontal_dir) {
+            length += glyph_info[i].x_advance;
+        } else {
+            length -= glyph_info[i].y_advance;
+        }
+    }
+
+    if (glyph_info) {
+        PyMem_Free(glyph_info);
+        glyph_info = NULL;
+    }
+
+    return PyLong_FromLong(length);
+}
+
 static PyObject*
 font_getsize(FontObject* self, PyObject* args)
 {
@@ -1176,6 +1219,7 @@ font_dealloc(FontObject* self)
 static PyMethodDef font_methods[] = {
     {"render", (PyCFunction) font_render, METH_VARARGS},
     {"getsize", (PyCFunction) font_getsize, METH_VARARGS},
+    {"getlength", (PyCFunction) font_getlength, METH_VARARGS},
 #if FREETYPE_MAJOR > 2 ||\
     (FREETYPE_MAJOR == 2 && FREETYPE_MINOR > 9) ||\
     (FREETYPE_MAJOR == 2 && FREETYPE_MINOR == 9 && FREETYPE_PATCH == 1)