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graft: fix invisible text appearing after strip_invisible_text #1448

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graft: fix invisible text appearing after strip_invisible_text #1448

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17 changes: 12 additions & 5 deletions src/ocrmypdf/_graft.py
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Original file line number Diff line number Diff line change
Expand Up @@ -57,27 +57,34 @@ def _update_resources(
fonts[font_key] = font



def strip_invisible_text(pdf: Pdf, page: Page):
stream = []
in_text_obj = False
render_mode = 0
render_mode_stack = [0]
text_objects = []

for operands, operator in parse_content_stream(page, ''):
if operator == Operator('Tr'):
render_mode_stack[-1] = operands[0]

if operator == Operator('q'):
render_mode_stack.append(render_mode_stack[-1])

if operator == Operator('Q'):
render_mode_stack.pop()

if not in_text_obj:
if operator == Operator('BT'):
in_text_obj = True
render_mode = 0
text_objects.append((operands, operator))
else:
stream.append((operands, operator))
else:
if operator == Operator('Tr'):
render_mode = operands[0]
text_objects.append((operands, operator))
if operator == Operator('ET'):
in_text_obj = False
if render_mode != 3:
if render_mode_stack[-1] != 3:
stream.extend(text_objects)
text_objects.clear()

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69 changes: 69 additions & 0 deletions tests/test_graft.py
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Original file line number Diff line number Diff line change
Expand Up @@ -40,3 +40,72 @@ def test_links(resources, outpdf):
p2 = pdf.pages[1]
assert p1.Annots[0].A.D[0].objgen == p2.objgen
assert p2.Annots[0].A.D[0].objgen == p1.objgen


def test_strip_invisble_text():
pdf = pikepdf.Pdf.new()
print(pikepdf.parse_content_stream(pikepdf.Stream(pdf, b'3 Tr')))
page = pdf.add_blank_page()
visible_text = [
pikepdf.ContentStreamInstruction((), pikepdf.Operator('BT')),
pikepdf.ContentStreamInstruction(
(pikepdf.Name('/F0'), 12), pikepdf.Operator('Tf')
),
pikepdf.ContentStreamInstruction((288, 720), pikepdf.Operator('Td')),
pikepdf.ContentStreamInstruction(
(pikepdf.String('visible'),), pikepdf.Operator('Tj')
),
pikepdf.ContentStreamInstruction((), pikepdf.Operator('ET')),
]
invisible_text = [
pikepdf.ContentStreamInstruction((), pikepdf.Operator('BT')),
pikepdf.ContentStreamInstruction(
(pikepdf.Name('/F0'), 12), pikepdf.Operator('Tf')
),
pikepdf.ContentStreamInstruction((288, 720), pikepdf.Operator('Td')),
pikepdf.ContentStreamInstruction(
(pikepdf.String('invisible'),), pikepdf.Operator('Tj')
),
pikepdf.ContentStreamInstruction((), pikepdf.Operator('ET')),
]
invisible_text_setting_tr = [
pikepdf.ContentStreamInstruction((), pikepdf.Operator('BT')),
pikepdf.ContentStreamInstruction([3], pikepdf.Operator('Tr')),
pikepdf.ContentStreamInstruction(
(pikepdf.Name('/F0'), 12), pikepdf.Operator('Tf')
),
pikepdf.ContentStreamInstruction((288, 720), pikepdf.Operator('Td')),
pikepdf.ContentStreamInstruction(
(pikepdf.String('invisible'),), pikepdf.Operator('Tj')
),
pikepdf.ContentStreamInstruction((), pikepdf.Operator('ET')),
]
stream = [
pikepdf.ContentStreamInstruction([], pikepdf.Operator('q')),
pikepdf.ContentStreamInstruction([3], pikepdf.Operator('Tr')),
*invisible_text,
pikepdf.ContentStreamInstruction([], pikepdf.Operator('Q')),
*visible_text,
*invisible_text_setting_tr,
*invisible_text,
]
content_stream = pikepdf.unparse_content_stream(stream)
page.Contents = pikepdf.Stream(pdf, content_stream)

def count(string, page):
return len(
[
True
for operands, operator in pikepdf.parse_content_stream(page)
if operator == pikepdf.Operator('Tj')
and operands[0] == pikepdf.String(string)
]
)

nr_visible_pre = count('visible', page)
ocrmypdf._graft.strip_invisible_text(pdf, page)
nr_visible_post = count('visible', page)
assert (
nr_visible_pre == nr_visible_post
), 'Number of visible text elements did not change'
assert count('invisible', page) == 0, 'No invisible elems left'
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