[bookmaker] / bookmaker.py

#!/usr/bin/env python3
"""
bookmaker.py is a helper for optimizing PDFs for the production of small self-printed, self-bound physical books.  Towards this goal it offers various PDF manipulation options that may also be used indepéndently and for other purposes.
"""
import argparse
import io
import os
import sys

def handled_error_exit(msg):
    print(f"ERROR: {msg}")
    sys.exit(1)

try:
    import pypdf
except ImportError:
    handled_error_exit("Can't run at all without pypdf installed.")

# some general paper geometry constants
POINTS_PER_CM = 10 * 72 / 25.4
A4_WIDTH = 21 * POINTS_PER_CM
A4_HEIGHT = 29.7 * POINTS_PER_CM
A4 = (A4_WIDTH, A4_HEIGHT)

# constants specifically for --nup4
A4_HALF_WIDTH = A4_WIDTH / 2
A4_HALF_HEIGHT = A4_HEIGHT / 2
CUT_DEPTH = 1.95 * POINTS_PER_CM
CUT_WIDTH = 1.05 * POINTS_PER_CM
MIDDLE_POINT_DEPTH = 0.4 * POINTS_PER_CM
INNER_SPINE_MARGIN_PER_PAGE = 1 * POINTS_PER_CM
QUARTER_SCALE_FACTOR = 0.5
PAGE_ORDER_FOR_NUP4 = (3,0,7,4,1,2,5,6)


class PageCrop:

    def __init__(self, left_cm=0, bottom_cm=0, right_cm=0, top_cm=0):
        self.left_cm = left_cm
        self.bottom_cm = bottom_cm
        self.right_cm = right_cm
        self.top_cm = top_cm
        self.left = float(self.left_cm) * POINTS_PER_CM
        self.bottom = float(self.bottom_cm) * POINTS_PER_CM
        self.right = float(self.right_cm) * POINTS_PER_CM
        self.top = float(self.top_cm) * POINTS_PER_CM
        zoom_horizontal = A4_WIDTH / (A4_WIDTH - self.left - self.right)
        zoom_vertical = A4_HEIGHT / (A4_HEIGHT - self.bottom - self.top)
        if (zoom_horizontal > 1 and zoom_vertical < 1) or (zoom_horizontal < 1 and zoom_vertical > 1):
            raise HandledException("-c: crops would create opposing zoom directions")
        elif zoom_horizontal + zoom_vertical > 2:
            self.zoom = min(zoom_horizontal, zoom_vertical)
        else:
            self.zoom = max(zoom_horizontal, zoom_vertical)

    def __str__(self):
        return str(vars(self))

    @property
    def format_in_cm(self):
        return f"left {self.left_cm}cm, bottom {self.bottom_cm}cm, right {self.right_cm}cm, top {self.top_cm}cm"

    @property
    def remaining_width(self):
        return A4_WIDTH - self.left - self.right

    @property
    def remaining_height(self):
        return A4_HEIGHT - self.bottom - self.top

    def give_mirror(self):
        return PageCrop(left_cm=self.right_cm, bottom_cm=self.bottom_cm, right_cm=self.left_cm, top_cm=self.top_cm)


class Nup4Geometry:

    def __init__(self, margin_cm):
        self.margin = margin_cm * POINTS_PER_CM
        self.shrink_for_margin = (A4_WIDTH - 2 * self.margin)/A4_WIDTH
        # NB: We define spine size un-shrunk, but .shrink_for_spine is used with values shrunk for the margin, which we undo here.
        spine_part_of_page = (INNER_SPINE_MARGIN_PER_PAGE / A4_HALF_WIDTH) / self.shrink_for_margin
        self.shrink_for_spine = 1 - spine_part_of_page


class HandledException(Exception):
    pass


def parse_args():
    help_epilogue = "See README.txt for detailed usage instructions, command examples, etc."
    parser = argparse.ArgumentParser(description=__doc__, epilog=help_epilogue, formatter_class=argparse.RawDescriptionHelpFormatter)
    parser.add_argument("-i", "--input_file", action="append", required=True, help="input PDF file")
    parser.add_argument("-o", "--output_file", required=True, help="output PDF file")
    parser.add_argument("-p", "--page_range", action="append", help="page range, e.g., '2-9' or '3-end' or 'start-14'")
    parser.add_argument("-c", "--crops", action="append", help="cm crops left, bottom, right, top – e.g., '10,10,10,10'; prefix with ':'-delimited page range to limit effect")
    parser.add_argument("-r", "--rotate_page", type=int, action="append", help="rotate page of number by 90° (usable multiple times on same page!)")
    parser.add_argument("-s", "--symmetry", action="store_true", help="alternate horizontal crops between odd and even pages")
    parser.add_argument("-n", "--nup4", action='store_true', help="puts 4 input pages onto 1 output page, adds binding cut stencil")
    parser.add_argument("-a", "--analyze", action="store_true", help="in --nup4, print lines identifying spine, page borders")
    parser.add_argument("-m", "--print_margin", type=float, default=0.43, help="print margin for --nup4 in cm (default 0.43)")
    return parser.parse_args()


def validate_inputs_first_pass(args):
    for filename in args.input_file:
        if not os.path.isfile(filename):
            raise HandledException(f"-i: {filename} is not a file")
        try:
            with open(filename, 'rb') as file:
                pypdf.PdfReader(file)
        except pypdf.errors.PdfStreamError:
            raise HandledException(f"-i: cannot interpret {filename} as PDF file")
    if args.page_range:
        for p_string in args.page_range:
            validate_page_range(p_string, "-p")
        if len(args.page_range) > len(args.input_file):
            raise HandledException("-p: more --page_range arguments than --input_file arguments")
    if args.crops:
        for c_string in args.crops:
            initial_split = c_string.split(':')
            if len(initial_split) > 2:
                raise HandledException(f"-c: cropping string has multiple ':': {c_string}")
            page_range, crops = split_crops_string(c_string)
            crops = crops.split(",")
            if page_range:
                validate_page_range(page_range, "-c")
            if len(crops) != 4:
                raise HandledException(f"-c: cropping does not contain exactly three ',': {c_string}")
            for crop in crops:
                try:
                    float(crop)
                except ValueError:
                    raise HandledException(f"-c: non-number crop in: {c_string}")
    if args.rotate_page:
        for r in args.rotate_page:
            try:
                int(r)
            except ValueError:
                raise HandledException(f"-r: non-integer value: {r}")
            if r < 1:
                raise HandledException(f"-r: value must not be <1: {r}")
    try:
        float(args.print_margin)
    except ValueError:
        raise HandledException(f"-m: non-float value: {arg.print_margin}")


def validate_page_range(p_string, err_msg_prefix):
    prefix = f"{err_msg_prefix}: page range string"
    if '-' not in p_string:
        raise HandledException(f"{prefix} lacks '-': {p_string}")
    tokens = p_string.split("-")
    if len(tokens) > 2:
        raise HandledException(f"{prefix} has too many '-': {p_string}")
    for i, token in enumerate(tokens):
        if token == "":
            continue
        if i == 0 and token == "start":
            continue
        if i == 1 and token == "end":
            continue
        try:
            int(token)
        except ValueError:
            raise HandledException(f"{prefix} carries value neither integer, nor 'start', nor 'end': {p_string}")
        if int(token) < 1:
            raise HandledException(f"{prefix} carries page number <1: {p_string}")
    start = -1
    end = -1
    try:
        start = int(tokens[0])
        end = int(tokens[1])
    except ValueError:
        pass
    if start > 0 and end > 0 and start > end:
        raise HandledException(f"{prefix} has higher start than end value: {p_string}")


def split_crops_string(c_string):
    initial_split = c_string.split(':')
    if len(initial_split) > 1:
        page_range = initial_split[0]
        crops = initial_split[1]
    else:
        page_range = None
        crops = initial_split[0]
    return page_range, crops


def parse_page_range(range_string, pages):
    start_page = 0
    end_page = len(pages)
    if range_string:
        start, end = range_string.split('-')
        if not (len(start) == 0 or start == "start"):
            start_page = int(start) - 1
        if not (len(end) == 0 or end == "end"):
            end_page = int(end)
    return start_page, end_page


def read_inputs_to_pagelist(args_input_file, args_page_range):
    pages_to_add = []
    opened_files = []
    new_page_num = 0
    for i, input_file in enumerate(args_input_file):
        file = open(input_file, 'rb')
        opened_files += [file]
        reader = pypdf.PdfReader(file)
        range_string = None
        if args_page_range and len(args_page_range) > i:
            range_string = args_page_range[i]
        start_page, end_page = parse_page_range(range_string, reader.pages)
        if end_page > len(reader.pages):  # no need to test start_page cause start_page > end_page is checked above
            raise HandledException(f"-p: page range goes beyond pages of input file: {range_string}")
        for old_page_num in range(start_page, end_page):
            new_page_num += 1
            page = reader.pages[old_page_num]
            pages_to_add += [page]
            print(f"-i, -p: read in {input_file} page number {old_page_num+1} as new page {new_page_num}")
    return pages_to_add, opened_files


def validate_inputs_second_pass(args, pages_to_add):
    if args.crops:
        for c_string in args.crops:
            page_range, _= split_crops_string(c_string)
            if page_range:
                start, end = parse_page_range(page_range, pages_to_add)
                if end > len(pages_to_add):
                     raise HandledException(f"-c: page range goes beyond number of pages we're building: {page_range}")
    if args.rotate_page:
        for r in args.rotate_page:
            if r > len(pages_to_add):
                 raise HandledException(f"-r: page number beyond number of pages we're building: {r}")


def rotate_pages(args_rotate_page, pages_to_add):
    if args_rotate_page:
        for rotate_page in args_rotate_page:
            page = pages_to_add[rotate_page - 1]
            page.add_transformation(pypdf.Transformation().translate(tx=-A4_WIDTH/2, ty=-A4_HEIGHT/2))
            page.add_transformation(pypdf.Transformation().rotate(-90))
            page.add_transformation(pypdf.Transformation().translate(tx=A4_WIDTH/2, ty=A4_HEIGHT/2))
            print(f"-r: rotating (by 90°) page {rotate_page}")


def pad_pages_to_multiple_of_8(pages_to_add):
    mod_to_8 = len(pages_to_add) % 8
    if mod_to_8 > 0:
        old_len = len(pages_to_add)
        for _ in range(8 - mod_to_8):
            new_page = pypdf.PageObject.create_blank_page(width=A4_WIDTH, height=A4_HEIGHT)
            pages_to_add += [new_page]
        print(f"-n: number of input pages {old_len} not required multiple of 8, padded to {len(pages_to_add)}")


def normalize_pages_to_A4(pages_to_add):
    for page in pages_to_add:
        if "/Rotate" in page:  # TODO: preserve rotation, but in canvas?
            page.rotate(360 - page["/Rotate"])
        page.mediabox.left = 0
        page.mediabox.bottom = 0
        page.mediabox.top = A4_HEIGHT
        page.mediabox.right = A4_WIDTH
        page.cropbox = page.mediabox


def collect_per_page_crops_and_zooms(args_crops, args_symmetry, pages_to_add):
    crop_at_page = [PageCrop()] * len(pages_to_add)
    if args_crops:
        for c_string in args_crops:
            page_range, crops = split_crops_string(c_string)
            start_page, end_page = parse_page_range(page_range, pages_to_add)
            prefix = "-c, -t" if args_symmetry else "-c"
            suffix = " (but alternating left and right crop between even and odd pages)" if args_symmetry else ""
            page_crop = PageCrop(*[x for x in crops.split(',')])
            print(f"{prefix}: to pages {start_page + 1} to {end_page} applying crop: {page_crop.format_in_cm}{suffix}")
            for page_num in range(start_page, end_page):
                if args_symmetry and page_num % 2:
                    crop_at_page[page_num] = page_crop.give_mirror()
                else:
                    crop_at_page[page_num] = page_crop
    return crop_at_page


def build_single_pages_output(writer, pages_to_add, crop_at_page):
    print("building 1-input-page-per-output-page book")
    odd_page = True
    for i, page in enumerate(pages_to_add):
        page.add_transformation(pypdf.Transformation().translate(tx=-crop_at_page[i].left, ty=-crop_at_page[i].bottom))
        page.add_transformation(pypdf.Transformation().scale(crop_at_page[i].zoom, crop_at_page[i].zoom))
        page.mediabox.right = crop_at_page[i].remaining_width * crop_at_page[i].zoom
        page.mediabox.top = crop_at_page[i].remaining_height * crop_at_page[i].zoom
        writer.add_page(page)
        odd_page = not odd_page
        print(f"built page number {i+1} (of {len(pages_to_add)})")


def build_nup4_output(writer, pages_to_add, crop_at_page, args_print_margin, args_analyze, canvas_class):
    print("-n: building 4-input-pages-per-output-page book")
    print(f"-m: applying printable-area margin of {args_print_margin}cm")
    if args_analyze:
        print("-a: drawing page borders, spine limits")
    nup4_geometry = Nup4Geometry(args_print_margin)
    pages_to_add, new_i_order = resort_pages_for_nup4(pages_to_add)
    nup4_i = 0
    page_count = 0
    is_front_page = True
    for i, page in enumerate(pages_to_add):
        if nup4_i == 0:
            new_page = pypdf.PageObject.create_blank_page(width=A4_WIDTH, height=A4_HEIGHT)
        corrected_i = new_i_order[i]
        nup4_inner_page_transform(page, crop_at_page[corrected_i], nup4_geometry, nup4_i)
        nup4_outer_page_transform(page, nup4_geometry, nup4_i)
        new_page.merge_page(page)
        page_count += 1
        print(f"merged page number {page_count} (of {len(pages_to_add)})")
        nup4_i += 1
        if nup4_i > 3:
            ornate_nup4(writer, args_analyze, is_front_page, new_page, nup4_geometry, canvas_class)
            writer.add_page(new_page)
            nup4_i = 0
            is_front_page = not is_front_page


def resort_pages_for_nup4(pages_to_add):
    new_page_order = []
    new_i_order = []
    eight_pack = []
    i = 0
    n_eights = 0
    for page in pages_to_add:
        if i == 0:
            eight_pack = []
        eight_pack += [page]
        i += 1
        if i == 8:
            i = 0
            for n in PAGE_ORDER_FOR_NUP4:
                new_i_order += [8 * n_eights + n]
                new_page_order += [eight_pack[n]]
            n_eights += 1
    return new_page_order, new_i_order


def nup4_inner_page_transform(page, crop, nup4_geometry, nup4_i):
    page.add_transformation(pypdf.Transformation().translate(ty=(A4_HEIGHT / crop.zoom - (A4_HEIGHT - crop.top))))
    if nup4_i == 0 or nup4_i == 2:
        page.add_transformation(pypdf.Transformation().translate(tx=-crop.left))
    elif nup4_i == 1 or nup4_i == 3:
        page.add_transformation(pypdf.Transformation().translate(tx=(A4_WIDTH / crop.zoom - (A4_WIDTH - crop.right))))
    page.add_transformation(pypdf.Transformation().scale(crop.zoom * nup4_geometry.shrink_for_spine, crop.zoom * nup4_geometry.shrink_for_spine))
    if nup4_i == 2 or nup4_i == 3:
        page.add_transformation(pypdf.Transformation().translate(ty=-2*nup4_geometry.margin/nup4_geometry.shrink_for_margin))


def nup4_outer_page_transform(page, nup4_geometry, nup4_i):
    page.add_transformation(pypdf.Transformation().translate(ty=(1-nup4_geometry.shrink_for_spine)*A4_HEIGHT))
    if nup4_i == 0 or nup4_i == 1:
        y_section = A4_HEIGHT
        page.mediabox.bottom = A4_HALF_HEIGHT
        page.mediabox.top    = A4_HEIGHT
    if nup4_i == 2 or nup4_i == 3:
        y_section = 0
        page.mediabox.bottom = 0
        page.mediabox.top  =  A4_HALF_HEIGHT
    if nup4_i == 0 or nup4_i == 2:
        x_section = 0
        page.mediabox.left   = 0
        page.mediabox.right  = A4_HALF_WIDTH
    if nup4_i == 1 or nup4_i == 3:
        page.add_transformation(pypdf.Transformation().translate(tx=(1-nup4_geometry.shrink_for_spine)*A4_WIDTH))
        x_section = A4_WIDTH
        page.mediabox.left   = A4_HALF_WIDTH
        page.mediabox.right  = A4_WIDTH
    page.add_transformation(pypdf.Transformation().translate(tx=x_section, ty=y_section))
    page.add_transformation(pypdf.Transformation().scale(QUARTER_SCALE_FACTOR, QUARTER_SCALE_FACTOR))


def ornate_nup4(writer, args_analyze, is_front_page, new_page, nup4_geometry, canvas_class):
    if args_analyze:
        # borders
        packet = io.BytesIO()
        c = canvas_class(packet, pagesize=A4)
        c.setLineWidth(0.1)
        c.line(0, A4_HEIGHT, A4_WIDTH, A4_HEIGHT)
        c.line(0, A4_HALF_HEIGHT, A4_WIDTH, A4_HALF_HEIGHT)
        c.line(0, 0, A4_WIDTH, 0)
        c.line(0, A4_HEIGHT, 0, 0)
        c.line(A4_HALF_WIDTH, A4_HEIGHT, A4_HALF_WIDTH, 0)
        c.line(A4_WIDTH, A4_HEIGHT, A4_WIDTH, 0)
        c.save()
        new_pdf = pypdf.PdfReader(packet)
        new_page.merge_page(new_pdf.pages[0])
    printable_offset_x = nup4_geometry.margin
    printable_offset_y = nup4_geometry.margin * A4_HEIGHT / A4_WIDTH
    new_page.add_transformation(pypdf.Transformation().scale(nup4_geometry.shrink_for_margin, nup4_geometry.shrink_for_margin))
    new_page.add_transformation(pypdf.Transformation().translate(tx=printable_offset_x, ty=printable_offset_y))
    x_left_spine_limit = A4_HALF_WIDTH * nup4_geometry.shrink_for_spine
    x_right_spine_limit = A4_WIDTH - x_left_spine_limit
    if args_analyze or is_front_page:
        packet = io.BytesIO()
        c = canvas_class(packet, pagesize=A4)
    if args_analyze:
        # spine lines
        c.setLineWidth(0.1)
        c.line(x_left_spine_limit, A4_HEIGHT, x_left_spine_limit, 0)
        c.line(x_right_spine_limit, A4_HEIGHT, x_right_spine_limit, 0)
    if is_front_page:
        c.setLineWidth(0.2)
        draw_cut(c, x_left_spine_limit, (1))
        draw_cut(c, x_right_spine_limit, (-1))
    if args_analyze or is_front_page:
        c.save()
        new_pdf = pypdf.PdfReader(packet)
        new_page.merge_page(new_pdf.pages[0])


def draw_cut(canvas, x_spine_limit, direction):
    outer_start_x = x_spine_limit - 0.5 * CUT_WIDTH * direction
    inner_start_x = x_spine_limit + 0.5 * CUT_WIDTH * direction
    middle_point_y =  A4_HALF_HEIGHT + MIDDLE_POINT_DEPTH * direction
    end_point_y =  A4_HALF_HEIGHT + CUT_DEPTH * direction
    canvas.line(inner_start_x, A4_HALF_HEIGHT, x_spine_limit, end_point_y)
    canvas.line(x_spine_limit, end_point_y, x_spine_limit, middle_point_y)
    canvas.line(x_spine_limit, middle_point_y, outer_start_x, A4_HALF_HEIGHT)


def main():
    args = parse_args()
    validate_inputs_first_pass(args)
    if args.nup4:
        try:
            from reportlab.pdfgen.canvas import Canvas
        except ImportError:
            raise HandledException("-n: need reportlab.pdfgen.canvas installed for --nup4")
    pages_to_add, opened_files = read_inputs_to_pagelist(args.input_file, args.page_range)
    validate_inputs_second_pass(args, pages_to_add)
    rotate_pages(args.rotate_page, pages_to_add)
    if args.nup4:
        pad_pages_to_multiple_of_8(pages_to_add)
    normalize_pages_to_A4(pages_to_add)
    crop_at_page = collect_per_page_crops_and_zooms(args.crops, args.symmetry, pages_to_add)
    writer = pypdf.PdfWriter()
    if args.nup4:
        build_nup4_output(writer, pages_to_add, crop_at_page, args.print_margin, args.analyze, Canvas)
    else:
        build_single_pages_output(writer, pages_to_add, crop_at_page)
    for file in opened_files:
        file.close()
    with open(args.output_file, 'wb') as output_file:
        writer.write(output_file)


if __name__ == "__main__":
    try:
        main()
    except HandledException as e:
        handled_error_exit(e)