Bookmaker: some more refactoring.

diff --git a/bookmaker.py b/bookmaker.py
index 001877920d2cd1bb014ae2850e09726f6971fcbe..8df8814afbaeb496245d0b1be3e8af9aa178dc9e 100755 (executable)
--- a/bookmaker.py
+++ b/bookmaker.py
@@ -73,15 +73,20 @@ try:
 except ImportError:
     handled_error_exit("Can't run at all without pypdf installed.")
 
-# some constants
+# 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
 SPINE_LIMIT = 1 * POINTS_PER_CM
+QUARTER_SCALE_FACTOR = 0.5
 
 # some helpers
 class HandledException(Exception):
@@ -138,14 +143,14 @@ def parse_page_range(range_string, pages):
             end_page = int(end)
     return start_page, end_page
 
-def draw_cut(canvas, x_spine_limit, direction, half_height):
+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 = half_height + MIDDLE_POINT_DEPTH * direction
-    end_point_y = half_height + CUT_DEPTH * direction
-    canvas.line(inner_start_x, half_height, x_spine_limit, end_point_y)
+    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, half_height)
+    canvas.line(x_spine_limit, middle_point_y, outer_start_x, A4_HALF_HEIGHT)
 
 def parse_args():
     parser = argparse.ArgumentParser(description=__doc__, epilog=help_epilogue, formatter_class=argparse.RawDescriptionHelpFormatter)
@@ -330,13 +335,9 @@ def main():
         print(f"-m: applying printable-area margin of {args.print_margin}cm")
         if args.analyze:
             print("-a: drawing page borders, spine limits")
-        n_pages_per_axis = 2
         printable_margin = args.print_margin * POINTS_PER_CM
-        printable_scale = (A4_WIDTH - 2*printable_margin)/A4_WIDTH
-        half_width = A4_WIDTH / n_pages_per_axis
-        half_height = A4_HEIGHT / n_pages_per_axis
-        section_scale_factor = 1 / n_pages_per_axis
-        spine_part_of_page = (SPINE_LIMIT / half_width) / printable_scale
+        printable_scale = (A4_WIDTH - 2 * printable_margin)/A4_WIDTH
+        spine_part_of_page = (SPINE_LIMIT / A4_HALF_WIDTH) / printable_scale
         bonus_shrink_factor = 1 - spine_part_of_page
         new_page_order = []
         new_i_order = []
@@ -391,23 +392,23 @@ def main():
             page.add_transformation(pypdf.Transformation().translate(ty=(1-bonus_shrink_factor)*A4_HEIGHT))
             if i == 0 or i == 1:
                 y_section = A4_HEIGHT
-                page.mediabox.bottom = half_height
+                page.mediabox.bottom = A4_HALF_HEIGHT
                 page.mediabox.top    = A4_HEIGHT
             if i == 2 or i == 3:
                 y_section = 0
                 page.mediabox.bottom = 0
-                page.mediabox.top  =   half_height
+                page.mediabox.top  =  A4_HALF_HEIGHT
             if i == 0 or i == 2:
                 x_section = 0
                 page.mediabox.left   = 0
-                page.mediabox.right  = half_width
+                page.mediabox.right  = A4_HALF_WIDTH
             if i == 1 or i == 3:
                 page.add_transformation(pypdf.Transformation().translate(tx=(1-bonus_shrink_factor)*A4_WIDTH))
                 x_section = A4_WIDTH
-                page.mediabox.left   = half_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(section_scale_factor, section_scale_factor))
+            page.add_transformation(pypdf.Transformation().scale(QUARTER_SCALE_FACTOR, QUARTER_SCALE_FACTOR))
             new_page.merge_page(page)
             page_count += 1
             print(f"merged page number {page_count} (of {len(pages_to_add)})")
@@ -419,10 +420,10 @@ def main():
                     c = reportlab.pdfgen.canvas.Canvas(packet, pagesize=A4)
                     c.setLineWidth(0.1)
                     c.line(0, A4_HEIGHT, A4_WIDTH, A4_HEIGHT)
-                    c.line(0, half_height, A4_WIDTH, half_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(half_width, A4_HEIGHT, half_width, 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)
@@ -431,7 +432,7 @@ def main():
                 printable_offset_y = printable_margin * A4_HEIGHT / A4_WIDTH
                 new_page.add_transformation(pypdf.Transformation().scale(printable_scale, printable_scale))
                 new_page.add_transformation(pypdf.Transformation().translate(tx=printable_offset_x, ty=printable_offset_y))
-                x_left_spine_limit = half_width * bonus_shrink_factor
+                x_left_spine_limit = A4_HALF_WIDTH * bonus_shrink_factor
                 x_right_spine_limit = A4_WIDTH - x_left_spine_limit
                 if args.analyze or front_page:
                     packet = io.BytesIO()
@@ -443,8 +444,8 @@ def main():
                     c.line(x_right_spine_limit, A4_HEIGHT, x_right_spine_limit, 0)
                 if front_page:
                     c.setLineWidth(0.2)
-                    draw_cut(c, x_left_spine_limit, (1), half_height)
-                    draw_cut(c, x_right_spine_limit, (-1), half_height)
+                    draw_cut(c, x_left_spine_limit, (1))
+                    draw_cut(c, x_right_spine_limit, (-1))
                 if args.analyze or front_page:
                     c.save()
                     new_pdf = pypdf.PdfReader(packet)