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Add kerning to single-byte strings in PDFs #19582

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Merged
merged 2 commits into from
Mar 4, 2021
Merged

Add kerning to single-byte strings in PDFs #19582

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63af5a2
Add test case to check if kerning is added to pdf
sauerburger Mar 1, 2021
1251563
Add kerning to Type 3 font, ASCII strings in PDFs
sauerburger Feb 25, 2021
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24 changes: 13 additions & 11 deletions lib/matplotlib/backends/backend_pdf.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2287,24 +2287,26 @@ def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None):
}
self.file._annotations[-1][1].append(link_annotation)

# If fonttype != 3 or there are no multibyte characters, emit the whole
# string at once.
if fonttype != 3 or all(ord(char) <= 255 for char in s):
# If fonttype != 3 emit the whole string at once without manual
# kerning.
if fonttype != 3:
self.file.output(Op.begin_text,
self.file.fontName(prop), fontsize, Op.selectfont)
self._setup_textpos(x, y, angle)
self.file.output(self.encode_string(s, fonttype), Op.show,
Op.end_text)
self.file.output(self.encode_string(s, fonttype),
Op.show, Op.end_text)

# There is no way to access multibyte characters of Type 3 fonts, as
# they cannot have a CIDMap. Therefore, in this case we break the
# string into chunks, where each chunk contains either a string of
# consecutive 1-byte characters or a single multibyte character. Each
# chunk is emitted with a separate command: 1-byte characters use the
# regular text show command (Tj), whereas multibyte characters use
# the XObject command (Do). (If using Type 42 fonts, all of this
# complication is avoided, but of course, those fonts can not be
# subsetted.)
# consecutive 1-byte characters or a single multibyte character.
# A sequence of 1-byte characters is broken into multiple chunks to
# adjust the kerning between adjacent chunks. Each chunk is emitted
# with a separate command: 1-byte characters use the regular text show
# command (TJ) with appropriate kerning between chunks, whereas
# multibyte characters use the XObject command (Do). (If using Type
# 42 fonts, all of this complication is avoided, but of course,
# subsetting those fonts is complex/hard to implement.)
else:
# List of (start_x, [prev_kern, char, char, ...]), w/o zero kerns.
singlebyte_chunks = []
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Binary file added lib/matplotlib/tests/baseline_images/test_text/text_pdf_kerning.pdf
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6 changes: 6 additions & 0 deletions lib/matplotlib/tests/test_text.py
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Original file line number Diff line number Diff line change
Expand Up @@ -714,3 +714,9 @@ def test_update_mutate_input():
def test_invalid_color():
with pytest.raises(ValueError):
plt.figtext(.5, .5, "foo", c="foobar")


@image_comparison(['text_pdf_kerning.pdf'], style='mpl20')
def test_pdf_kerning():
plt.figure()
plt.figtext(0.1, 0.5, "ATATATATATATATATATA", size=30)