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README.md
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README.md
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== img2pdf ==
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Lossless conversion of images to PDF without unnecessarily re-encoding JPEG
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files. Thus, no loss of quality and no unnecessary large output file.
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PDF is able to embed JPEG images as they are without re-encoding them (and
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hence loosing quality) but I was missing a tool to do this automatically, thus
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I wrote this piece of python code.
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If you know how to embed JPEG images into a PDF container without
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recompression, using existing tools, please contact me so that I can put this
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code into the garbage bin :D
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The program will take image filenames from commandline arguments and output a
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PDF file with them embedded into it. If the input image is a JPEG file, it will
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be included as-is without any processing. If it is in any other format, the
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image will be included as zip-encoded RGB. As a result, this tool will be able
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to lossless wrap any image into a PDF container while performing better (in
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terms of quality/filesize ratio) than existing tools in case the input image is
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a JPEG.
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For the record, the imagemagick command to lossless convert any image to
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PDF using zip-encoding, is:
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convert input.jpg -compress Zip output.pdf
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The downside is, that using imagemagick like this will make the resulting PDF
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files a few times bigger than the input JPEG and can also not output a
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multipage PDF.
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img2pdf is able to output a PDF with multiple pages if more than one input
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image is given, losslessly embed JPEGs into a PDF container without adding more
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overhead than the PDF structure itself and will save all other graphics formats
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using lossless zip-compression.
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If you find a JPEG that, when embedded can not be read by the Adobe Acrobat
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Reader, please contact me.
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For lossless conversion of other formats than JPEG, zip/flate encoding is used.
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This choice is based on a number of tests I did on images. I converted them
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into PDF using imagemagick and all compressions it has to offer and then
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compared the output size of the lossless variants. In all my tests, zip/flate
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encoding performed best. You can verify my findings using the test_comp.sh
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script with any input image given as a commandline argument. If you find an
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input file that is outperformed by another lossless compression, contact me.
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img2pdf.py
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img2pdf.py
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#!/usr/bin/env python
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import Image
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import sys
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import zlib
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import argparse
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from datetime import datetime
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def parse(cont, indent=1):
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if type(cont) is dict:
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return "<<\n"+"\n".join([4*indent*" "+"%s %s"%(k, parse(v, indent+1)) for k, v in cont.items()])+"\n"+4*(indent-1)*" "+">>"
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elif type(cont) is int or type(cont) is float:
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return str(cont)
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elif isinstance(cont, obj):
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return "%d 0 R"%cont.get_identifier()
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elif type(cont) is str:
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return cont
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elif type(cont) is list:
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return "[ "+" ".join([parse(c, indent) for c in cont])+" ]"
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class obj():
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def __init__(self, content, stream=None):
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self.content = content
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self.stream = stream
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def tostring(self, identifier):
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self.identifier = identifier
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if self.stream:
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return "%d 0 obj "%identifier+parse(self.content)+"\nstream\n"+self.stream+"\nendstream\nendobj\n"
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else:
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return "%d 0 obj "%identifier+parse(self.content)+" endobj\n"
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def get_identifier(self):
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if not hasattr(self, 'identifier'):
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raise Exception("no id set yet, call tostring() on obj first")
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return self.identifier
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def main(images, dpi, title=None, author=None, creator=None, producer=None,
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creationdate=None, moddate=None, subject=None, keywords=None):
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now = datetime.now()
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info = dict()
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if title:
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info["/Title"] = "("+title+")"
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if author:
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info["/Author"] = "("+author+")"
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if creator:
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info["/Creator"] = "("+creator+")"
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if producer:
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info["/Producer"] = "("+producer+")"
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if creationdate:
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info["/CreationDate"] = "(D:"+creationdate.strftime("%Y%m%d%H%M%S")+")"
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else:
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info["/CreationDate"] = "(D:"+now.strftime("%Y%m%d%H%M%S")+")"
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if moddate:
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info["/ModDate"] = "(D:"+moddate.strftime("%Y%m%d%H%M%S")+")"
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else:
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info["/ModDate"] = "(D:"+now.strftime("%Y%m%d%H%M%S")+")"
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if subject:
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info["/Subject"] = "("+subject+")"
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if keywords:
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info["/Keywords"] = "("+",".join(keywords)+")"
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info = obj(info)
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pagestuples = list()
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for im in images:
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imgdata = Image.open(im)
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width, height = imgdata.size
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if dpi:
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dpi_x, dpi_y = dpi, dpi
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else:
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dpi_x, dpi_y = imgdata.info.get("dpi", (96, 96))
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pdf_x, pdf_y = 72.0*width/dpi_x, 72.0*height/dpi_y # pdf units = 1/72 inch
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imgformat = imgdata.format
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color = imgdata.mode
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if color == 'L':
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color = "/DeviceGray"
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elif color == 'RGB':
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color = "/DeviceRGB"
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else:
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print "unsupported color space:", color
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exit(1)
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# either embed the whole jpeg or deflate the bitmap representation
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if imgformat is "JPEG":
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ofilter = [ "/DCTDecode" ]
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im.seek(0)
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imgdata = im.read()
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else:
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ofilter = [ "/FlateDecode" ]
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imgdata = zlib.compress(imgdata.tostring())
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im.close()
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image = obj({
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"/Type": "/XObject",
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"/Subtype": "/Image",
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"/Filter": ofilter,
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"/Width": width,
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"/Height": height,
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"/ColorSpace": color,
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"/BitsPerComponent": 8, # hardcoded as PIL doesnt provide bits for non-jpeg formats
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"/Length": len(imgdata)
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}, imgdata)
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text = "q\n%f 0 0 %f 0 0 cm\n/Im0 Do\nQ"%(pdf_x, pdf_y)
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content = obj({
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"/Length": len(text)
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}, text)
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page = obj({
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"/Type": "/Page",
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"/Resources": {
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"/XObject": {
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"/Im0": image
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}
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},
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"/MediaBox": [0, 0, pdf_x, pdf_y],
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"/Contents": content
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})
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pagestuples.append((image, content, page))
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pages = obj({
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"/Type": "/Pages",
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"/Kids": [ pagetuple[2] for pagetuple in pagestuples ],
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"/Count": len(pagestuples)
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})
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catalog = obj({
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"/Pages": pages,
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"/Type": "/Catalog"
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})
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objects = list()
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objects.append(info.tostring(3*(len(pagestuples)+1)))
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for i, (image, content, page) in enumerate(reversed(pagestuples)):
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objects.append(image.tostring(3*(len(pagestuples)-i+1)-1))
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objects.append(content.tostring(3*(len(pagestuples)-i+1)-2))
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objects.append(page.tostring(3*(len(pagestuples)-i+1)-3))
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objects.append(pages.tostring(2))
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objects.append(catalog.tostring(1))
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objects.reverse()
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xreftable = list()
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result = "%PDF-1.3\n"
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xreftable.append("0000000000 65535 f \n")
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for o in objects:
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xreftable.append("%010d 00000 n \n"%len(result))
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result += o
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xrefoffset = len(result)
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result += "xref\n"
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result += "0 %d\n"%len(xreftable)
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for x in xreftable:
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result += x
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result += "trailer\n"
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result += parse({"/Size": len(xreftable), "/Info": info, "/Root": catalog})+"\n"
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result += "startxref\n"
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result += "%d\n"%xrefoffset
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result += "%%EOF\n"
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return result
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if __name__ == "__main__":
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parser = argparse.ArgumentParser(description='lossless conversion/embedding of images (in)to pdf')
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parser.add_argument('images', metavar='infile', type=argparse.FileType('r'),
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nargs='*', default=[sys.stdin], help='input file(s) (default: stdin)')
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parser.add_argument('-o', '--output', metavar='out', type=argparse.FileType('w'),
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default=sys.stdout, help='output file (default: stdout)')
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def positive_float(string):
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value = float(string)
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if value <= 0:
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msg = "%r is not positive"%string
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raise argparse.ArgumentTypeError(msg)
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return value
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parser.add_argument('-d', '--dpi', metavar='dpi', type=positive_float, help='dpi for pdf output (default: 96.0)')
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parser.add_argument('-t', '--title', metavar='title', type=str, help='title for metadata')
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parser.add_argument('-a', '--author', metavar='author', type=str, help='author for metadata')
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parser.add_argument('-c', '--creator', metavar='creator', type=str, help='creator for metadata')
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parser.add_argument('-p', '--producer', metavar='producer', type=str, help='producer for metadata')
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def valid_date(string):
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return datetime.strptime(string, "%Y-%m-%dT%H:%M:%S")
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parser.add_argument('-r', '--creationdate', metavar='creationdate',
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type=valid_date, help='creation date for metadata in YYYY-MM-DDTHH:MM:SS format')
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parser.add_argument('-m', '--moddate', metavar='moddate',
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type=valid_date, help='modification date for metadata in YYYY-MM-DDTHH:MM:SS format')
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parser.add_argument('-s', '--subject', metavar='subject', type=str, help='subject for metadata')
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parser.add_argument('-k', '--keywords', metavar='kw', type=str, nargs='+', help='keywords for metadata')
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args = parser.parse_args()
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args.output.write(main(args.images, args.dpi, args.title, args.author,
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args.creator, args.producer, args.creationdate, args.moddate,
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args.subject, args.keywords))
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