Meta/jbig2_to_pdf.py: Read jbig2 dimensions from file

Since we're parsing segment headers for random-access jbig2 inputs
already, just always do that and get the image dimensions from the
PageInformation segment data. Not all that much more code, and it
makes this script much more pleasant to use.
This commit is contained in:
Nico Weber 2024-04-01 20:36:11 -07:00 committed by Tim Flynn
parent 05844141bf
commit 7fc4ea5495
Notes: sideshowbarker 2024-07-17 05:01:20 +09:00

View file

@ -4,8 +4,8 @@
Creates a PDF that embeds a jbig2 image. Useful for viewing .jbig2 files in
PDF viewers, since all PDF viewers support .jbig2 but few image viewers do.
Usage is a bit clunky (use Build/lagom/bin/file to get the dimensions):
% Meta/jbig2_to_pdf.py -o foo.pdf path/to/bitmap.jbig2 399 400
Usage :
% Meta/jbig2_to_pdf.py -o foo.pdf path/to/bitmap.jbig2
% open foo.pdf
"""
@ -15,6 +15,7 @@ import struct
import textwrap
PageInformation = 48
EndOfFile = 51
@ -28,6 +29,7 @@ class SegmentHeader:
type: int
bytes: bytes
data_size: int
data: bytes
def read_segment_header(data, offset):
@ -59,45 +61,60 @@ def read_segment_header(data, offset):
segment_header_size += 4
bytes = data[offset:offset + segment_header_size]
return SegmentHeader(segment_header_size, type, bytes, data_size)
return SegmentHeader(segment_header_size, type, bytes, data_size, None)
def random_access_to_sequential(data):
def read_segment_headers(data, is_random_access):
offset = 0
segment_headers = []
while True:
while offset < len(data):
segment_header = read_segment_header(data, offset)
offset += segment_header.segment_header_size
if not is_random_access:
segment_header.data = data[offset:offset + segment_header.data_size]
offset += segment_header.data_size
segment_headers.append(segment_header)
offset += segment_header.segment_header_size
if segment_header.type == EndOfFile:
break
if is_random_access:
for segment_header in segment_headers:
segment_header.data = data[offset:offset + segment_header.data_size]
offset += segment_header.data_size
return segment_headers
def random_access_to_sequential(segment_headers):
out_data = bytes()
for segment_header in segment_headers:
out_data += segment_header.bytes
out_data += data[offset:offset + segment_header.data_size]
offset += segment_header.data_size
out_data += segment_header.data
return out_data
def get_dimensions(segment_headers):
for segment_header in segment_headers:
if segment_header.type != PageInformation:
continue
return struct.unpack_from('>II', segment_header.data)
raise Exception('did not find PageInformation')
def main():
parser = argparse.ArgumentParser(
epilog=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter
)
parser.add_argument("image", help="Input image")
parser.add_argument("width", type=int, help="image width")
parser.add_argument("height", type=int, help="image height")
parser.add_argument("-o", "--output", help="Path to output PDF")
args = parser.parse_args()
width, height = args.width, args.height
with open(args.image, 'rb') as f:
image_data = f.read()
print(f'dims {width}x{height}')
# strip jbig2 header
image_data = image_data[8:]
@ -106,8 +123,13 @@ def main():
image_data = image_data[4:]
image_data = image_data[1:]
segment_headers = read_segment_headers(image_data, is_random_access)
width, height = get_dimensions(segment_headers)
print(f'dims {width}x{height}')
if is_random_access:
image_data = random_access_to_sequential(image_data)
image_data = random_access_to_sequential(segment_headers)
start = dedent(b'''\
%PDF-1.4