03dbe317c5
Uneven folios are awkward, and folios of many different sizes are hard to bind correctly. Therefore, try to partition the sheets as folios of max_folio_size and max_folio_size - k, where k is minimal.
137 lines
5.8 KiB
Python
Executable file
137 lines
5.8 KiB
Python
Executable file
#!/usr/bin/env python3
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import argparse
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from pypdf import PaperSize, PdfReader, PdfWriter, Transformation
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from pypdf.annotations import Line
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from pypdf.generic import ArrayObject, FloatObject, NameObject
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import math
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def append_folio_A6(input_pdf, offset, size, append_to):
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# Handles edge case where folio has 1 page
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num_A5 = min(math.ceil(size / 4.0) * 2, size)
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writer = append_to
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w_offset = len(writer.pages)
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for i in range(num_A5):
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dpage = writer.add_blank_page(width=PaperSize.A5.height,
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height=PaperSize.A5.width)
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ipage = input_pdf.pages[i+offset]
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ipage.mediabox = dpage.mediabox
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if i % 2 == 0: # Even pages are filled right to left
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ipage.add_transformation(Transformation().translate(PaperSize.A6.width,
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0))
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dpage.merge_page(ipage)
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# Now for the fun part: work backwards to fill the remaining pages
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for j in range(size - num_A5):
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dpage = writer.pages[w_offset + num_A5 - 1 - j]
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ipage = input_pdf.pages[num_A5+j+offset]
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ipage.mediabox = dpage.mediabox
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if (num_A5 - 1 - j) % 2 == 1:
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ipage.add_transformation(Transformation().translate(PaperSize.A6.width,
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0))
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dpage.merge_page(ipage)
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return writer
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# Tries to find a partition as
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# num_sheets = max_folio_size * a + (max_folio_size - k) * b
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# where k is minimal. We let n = max_folio_size and L = num_sheets.
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# Note that when L > n^2, then k = 1 must succeed.
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def find_partition(num_sheets, max_folio_size):
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max_a = num_sheets // max_folio_size
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for k in range(1, max_folio_size):
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# We want to solve a*k = L (mod n-k). This happens iff
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# a*k' = L' (mod m') where k,L,m are divided by their gcd.
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# Then, if k' and m' have a common factor, L' doesn't have it and there
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# are no solutions. Otherwise, there's one solution mod m'.
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g = math.gcd(max_folio_size - k, k, num_sheets)
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mprime = (max_folio_size - k)//g
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kprime = k//g
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Lprime = num_sheets//g
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if (math.gcd(kprime, mprime) > 1):
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continue
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a_mod_mprime = (pow(kprime, -1, mprime) * Lprime) % mprime
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tosub = (max_a - a_mod_mprime + mprime) % mprime
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# If we're a bit above, substract only a little. But a bit below implies
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# substracting almost mprime.
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candidate = max_a - tosub
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if (candidate >= 0):
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return (candidate, k)
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# Interprets input_pdf as a list of A6 pages, and appends to append_to with
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# A5 pages using the following rules:
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# a. Odd/even page pairs correspond to front/back pages of a single sheet, printed
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# with "mirror around **short** edge"
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# b. when grouped as consecutive sequences of max_folio_size or less, the printed
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# sheets can be folded in the middle and assembled as a folio
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def foliate_A6(input_pdf, max_folio_size=-1, append_to=PdfWriter()):
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current_page = 0
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doc_length = len(input_pdf.pages)
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writer = append_to
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if max_folio_size < 0:
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max_folio_size = doc_length
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folio_page_size = 0
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while(current_page < doc_length):
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# max_folio_size is a number of _sheets_, each containing 4 pages
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folio_page_size = min(doc_length - current_page, 4*max_folio_size)
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append_folio_A6(input_pdf, current_page, folio_page_size, append_to)
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current_page += folio_page_size
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print("Dangling folio has",folio_page_size,"pages",
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"(",int(math.ceil(folio_page_size/4.0)),"sheets).")
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return writer
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# Take an A5 printing plan, with odd/even pages being understood
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# as front/back pairs of sheets, short edge mirroring. Produces an A4 printing plan
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# containing two A5 panels per sheet, long edge mirroring.
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def blit_to_A4(input_pdf, append_to=PdfWriter()):
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L = len(input_pdf.pages)
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writer = append_to
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for k in range(0, L, 2):
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if(k%4 == 0): # Open up a new sheet
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front_page = writer.add_blank_page(width=PaperSize.A4.width,
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height=PaperSize.A4.height)
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back_page = writer.add_blank_page(width=PaperSize.A4.width,
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height=PaperSize.A4.height)
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midline = Line(rect = (0, PaperSize.A4.height/2, PaperSize.A4.width, PaperSize.A4.height/2),
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p1=(10, PaperSize.A4.height/2),
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p2=(PaperSize.A4.width-10, PaperSize.A4.height/2))
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midline.flags = 4 # print the midline
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midline[NameObject("/C")] = ArrayObject([FloatObject(0.5)])
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writer.add_annotation(front_page, midline)
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front = input_pdf.pages[k]
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back = input_pdf.pages[k+1] if (k+1<L) else create_blank_page(None, PaperSize.A5.width, PaperSize.A5.height)
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front.mediabox = front_page.mediabox
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back.mediabox = back_page.mediabox
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if(k%4 == 0): # Translate to bottom half of page
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front.add_transformation(Transformation().translate(0, PaperSize.A5.width))
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back.add_transformation(Transformation().translate(0, PaperSize.A5.width))
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front_page.merge_page(front)
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back_page.merge_page(back)
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return writer
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parser = argparse.ArgumentParser()
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parser.add_argument("infile", help="input document, A6 pages")
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parser.add_argument("outfile", help="output document")
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parser.add_argument("-a5", help="output as a5, reverse on short edge",
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action="store_true")
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parser.add_argument("-fs", help="maximum folio size, in sheets",
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action="store", default=-1, type=int)
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args = parser.parse_args()
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input_pdf = PdfReader(args.infile)
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a5 = foliate_A6(input_pdf, args.fs)
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if (args.a5):
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a5.write(args.outfile)
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else:
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a4 = blit_to_A4(a5)
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a4.write(args.outfile)
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