Rasterize dvi files without dvipng

anntzer · QuLogic · commit 762711831e7d · 2026-02-05T14:36:39.000-05:00
This patch drops the reliance on dvipng to rasterize dvi files prior to
inclusion by agg, instead performing the rasterization ourselves (as a
consequence, the rasterization output also becomes dependent of the
freetype version used).  Note that this approach will be needed anyways
to support xetex and luatex, as dvipng doesn't support dvi files
generated by these engines.

Baseline images change slightly, for the better or the worse.  The
top-left blue cross text in test_rotation.py ("Myrt0") seems to be
better top-aligned against the blue line (the old version overshot a
bit); the bounding box of the formulas in test_usetex.py seems a bit
worse.
diff --git a/lib/matplotlib/backends/backend_agg.py b/lib/matplotlib/backends/backend_agg.py
@@ -31,6 +31,7 @@
 from matplotlib import _api, cbook
 from matplotlib.backend_bases import (
     _Backend, FigureCanvasBase, FigureManagerBase, RendererBase)
+from matplotlib.dviread import Dvi
 from matplotlib.font_manager import fontManager as _fontManager, get_font
 from matplotlib.ft2font import LoadFlags, RenderMode
 from matplotlib.mathtext import MathTextParser
@@ -266,19 +267,84 @@ def get_text_width_height_descent(self, s, prop, ismath):
     def draw_tex(self, gc, x, y, s, prop, angle, *, mtext=None):
         # docstring inherited
         # todo, handle props, angle, origins
+
         size = prop.get_size_in_points()
 
-        texmanager = self.get_texmanager()
+        if mpl.rcParams["text.latex.engine"] == "latex+dvipng":
+            Z = self.get_texmanager().get_grey(s, size, self.dpi)
+            Z = (Z * 0xff).astype(np.uint8)
+            w, h, d = self.get_text_width_height_descent(s, prop, ismath="TeX")
+            xd = d * math.sin(math.radians(angle))
+            yd = d * math.cos(math.radians(angle))
+            x = round(x + xd)
+            y = round(y + yd)
+            self._renderer.draw_text_image(Z, x, y, angle, gc)
+            return
+
+        dvifile = self.get_texmanager().make_dvi(s, size)
+        with Dvi(dvifile, self.dpi) as dvi:
+            page, = dvi
 
-        Z = texmanager.get_grey(s, size, self.dpi)
-        Z = np.array(Z * 255.0, np.uint8)
+        cos = math.cos(math.radians(angle))
+        sin = math.sin(math.radians(angle))
 
-        w, h, d = self.get_text_width_height_descent(s, prop, ismath="TeX")
-        xd = d * math.sin(math.radians(angle))
-        yd = d * math.cos(math.radians(angle))
-        x = round(x + xd)
-        y = round(y + yd)
-        self._renderer.draw_text_image(Z, x, y, angle, gc)
+        for text in page.text:
+            hf = mpl.rcParams["text.hinting_factor"]
+            # Resolving text.index will implicitly call get_font(), which
+            # resets the font transform, so it has to be done before explicitly
+            # setting the font transform below.
+            index = text.index
+            font = get_font(text.font_path)
+            font.set_size(text.font_size, self.dpi)
+            slant = text.font_effects.get("slant", 0)
+            extend = text.font_effects.get("extend", 1)
+            font._set_transform(
+                (0x10000 * np.array([[cos, -sin], [sin, cos]])
+                 @ [[extend, extend * slant], [0, 1]]
+                 @ [[1 / hf, 0], [0, 1]]).round().astype(int),
+                [round(0x40 * (x + text.x * cos - text.y * sin)),
+                 # FreeType's y is upwards.
+                 round(0x40 * (self.height - y + text.x * sin + text.y * cos))]
+            )
+            bitmap = font._render_glyph(
+                index, get_hinting_flag(),
+                RenderMode.NORMAL if gc.get_antialiased() else RenderMode.MONO)
+            buffer = np.asarray(bitmap.buffer)
+            if not gc.get_antialiased():
+                buffer *= 0xff
+            # draw_text_image's y is downwards & the bitmap bottom side.
+            self._renderer.draw_text_image(
+                buffer,
+                bitmap.left, int(self.height) - bitmap.top + buffer.shape[0],
+                0, gc)
+
+        rgba = gc.get_rgb()
+        if len(rgba) == 3 or gc.get_forced_alpha():
+            rgba = rgba[:3] + (gc.get_alpha(),)
+        gc1 = self.new_gc()
+        gc1.set_linewidth(0)
+        gc1.set_snap(gc.get_snap())
+        for box in page.boxes:
+            bx = box.x
+            by = box.y
+            bw = box.width
+            bh = box.height
+            if gc1.get_snap() in [None, True]:
+                # Prevent thin bars from disappearing by growing symmetrically.
+                if bw < 1:
+                    bx -= (1 - bw) / 2
+                    bw = 1
+                if bh < 1:
+                    by -= (1 - bh) / 2
+                    bh = 1
+            path = Path._create_closed([
+                (bx, by), (bx + bw, by), (bx + bw, by + bh), (bx, by + bh)])
+            self._renderer.draw_path(
+                gc1, path,
+                mpl.transforms.Affine2D()
+                .rotate_deg(angle).translate(x, self.height - y),
+                rgba)
+        gc1.restore()
 
     def get_canvas_width_height(self):
         # docstring inherited
diff --git a/lib/matplotlib/mpl-data/matplotlibrc b/lib/matplotlib/mpl-data/matplotlibrc
@@ -331,6 +331,16 @@
                      # zapf chancery, charter, serif, sans-serif, helvetica,
                      # avant garde, courier, monospace, computer modern roman,
                      # computer modern sans serif, computer modern typewriter
+
+## The TeX engine/format to use.  The following values are supported:
+## - "latex": The classic TeX engine (the current default).  All backends render
+##    TeX's output by parsing the DVI output into glyphs and boxes and emitting
+##    those one by one.
+## - "latex+dvipng": The same as "latex", with the exception that Agg-based
+##   backends rely on dvipng to rasterize TeX's output.  This value was the
+##   default up to Matplotlib 3.10.
+#text.latex.engine: latex
+
 #text.latex.preamble:   # IMPROPER USE OF THIS FEATURE WILL LEAD TO LATEX FAILURES
                         # AND IS THEREFORE UNSUPPORTED. PLEASE DO NOT ASK FOR HELP
                         # IF THIS FEATURE DOES NOT DO WHAT YOU EXPECT IT TO.
diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -1073,6 +1073,7 @@ def _convert_validator_spec(key, conv):
     # text props
     "text.color":          validate_color,
     "text.usetex":         validate_bool,
+    "text.latex.engine":   ["latex", "latex+dvipng"],
     "text.latex.preamble": validate_string,
     "text.hinting":        ["default", "no_autohint", "force_autohint",
                             "no_hinting", "auto", "native", "either", "none"],
@@ -1831,6 +1832,20 @@ class _Param:
                     "monospace, computer modern roman, computer modern sans serif, "
                     "computer modern typewriter"
     ),
+    _Param(
+        "text.latex.engine",
+        default="latex",
+        validator=["latex", "latex+dvipng"],
+        description=(
+            "The TeX engine/format to use.  The following values are supported:\n"
+            "- 'latex': The classic TeX engine (the current default).  All backends "
+            "render TeX's output by parsing the DVI output into glyphs and boxes and "
+            "emitting those one by one.\n"
+            "- 'latex+dvipng': The same as 'latex', with the exception that Agg-based "
+            "backends rely on dvipng to rasterize TeX's output.  This value was the "
+            "default up to Matplotlib 3.10."
+        )
+    ),
     _Param(
         "text.latex.preamble",
         default="",
diff --git a/lib/matplotlib/typing.py b/lib/matplotlib/typing.py
@@ -452,6 +452,7 @@
     "text.hinting_factor",
     "text.kerning_factor",
     "text.language",
+    "text.latex.engine",
     "text.latex.preamble",
     "text.parse_math",
     "text.usetex",
diff --git a/src/ft2font_wrapper.cpp b/src/ft2font_wrapper.cpp
@@ -971,7 +971,7 @@ const char *PyFT2Font_draw_glyph_to_bitmap__doc__ = R"""(
     image : 2d array of uint8
         The image buffer on which to draw the glyph.
     x, y : int
-        The pixel location at which to draw the glyph.
+        The position of the glyph's top left corner.
     glyph : Glyph
         The glyph to draw.
     antialiased : bool, default: True
