From 4ddef37cef61f28e32d1cf5bb45027a6217f1aef Mon Sep 17 00:00:00 2001
From: Taka <taka@vm-linux-dev>
Date: Sun, 25 Apr 2021 06:12:58 +1000
Subject: [PATCH] Allow PDF's to be compressed.

---
 asl_rulebook2/webapp/static/SearchResult.js |  2 +-
 bin/{add_pdf_dests.py => prepare_pdf.py}    | 49 ++++++++++++++++-----
 2 files changed, 40 insertions(+), 11 deletions(-)
 rename bin/{add_pdf_dests.py => prepare_pdf.py} (57%)

diff --git a/asl_rulebook2/webapp/static/SearchResult.js b/asl_rulebook2/webapp/static/SearchResult.js
index 865bd54..6cf9758 100644
--- a/asl_rulebook2/webapp/static/SearchResult.js
+++ b/asl_rulebook2/webapp/static/SearchResult.js
@@ -215,7 +215,7 @@ gMainApp.component( "ruleid", {
     } ; },
 
     // NOTE: This bit of HTML is sensitive to spaces :-/
-    // NOTE: Unfortunately, PDF destinations can't have spaces (see add_pdf_dests.py), so we need to
+    // NOTE: Unfortunately, PDF destinations can't have spaces (see prepare_pdf.py), so we need to
     // do a bit of hackery to simulate them :-( We could allow spaces in the ruleid's, and transparently
     // convert them to underscores when we create the PDF destinations, but it's probably better
     // to force them to be defined with underscores (and convert them to spaces in the UI), so that
diff --git a/bin/add_pdf_dests.py b/bin/prepare_pdf.py
similarity index 57%
rename from bin/add_pdf_dests.py
rename to bin/prepare_pdf.py
index 2bcb8f8..313ab47 100755
--- a/bin/add_pdf_dests.py
+++ b/bin/prepare_pdf.py
@@ -10,6 +10,17 @@ import click
 
 from asl_rulebook2.utils import TempFile
 
+# NOTE: "screen" gives significant savings (~65%) but scanned PDF's become very blurry. The main MMP eASLRB
+# is not too bad, but some images are also a bit unclear. "ebook" gives no savings for scanned PDF's, but
+# the main MMP eASLRB is quite usable, and only slightly larger (43 MB vs. 35 MB), so we use that.
+_COMPRESSION_CHOICES = [
+    "screen", # 72 dpi
+    "ebook", # 150 dpi
+    "printer", # 300 dpi
+    "prepress", # 300 dpi, color preserving
+    "none"
+]
+
 # ---------------------------------------------------------------------
 
 @click.command()
@@ -22,24 +33,42 @@ from asl_rulebook2.utils import TempFile
 @click.option( "--output","-o","output_fname", required=True, type=click.Path(dir_okay=False),
     help="Output PDF file."
 )
+@click.option( "--compression", type=click.Choice(_COMPRESSION_CHOICES), default="ebook",
+    help="Level of compression."
+)
 @click.option( "--gs","gs_path", default="gs",  help="Path to the Ghostscript executable." )
-def main( pdf_file, title, targets_fname, yoffset, output_fname, gs_path ):
+def main( pdf_file, title, targets_fname, yoffset, output_fname, compression, gs_path ):
     """Add named destinations to a PDF file."""
 
     # load the targets
     with open( targets_fname, "r" ) as fp:
         targets = json.load( fp )
 
-    with TempFile( mode="w" ) as temp_file:
+    with TempFile(mode="w") as compressed_file, TempFile(mode="w") as pdfmarks_file:
+
+        # compress the PDF
+        if compression and compression != "none":
+            print( "Compressing the PDF ({})...".format( compression ) )
+            compressed_file.close( delete=False )
+            args = [ gs_path, "-sDEVICE=pdfwrite", "-dNOPAUSE", "-dQUIET", "-dBATCH",
+                "-dPDFSETTINGS=/{}".format( compression ),
+                "-sOutputFile={}".format( compressed_file.name ),
+                pdf_file
+            ]
+            start_time = time.time()
+            subprocess.run( args, check=True )
+            elapsed_time = time.time() - start_time
+            print( "- Elapsed time: {}".format( datetime.timedelta(seconds=int(elapsed_time)) ) )
+            pdf_file = compressed_file.name
 
         # generate the pdfmarks
         print( "Generating the pdfmarks..." )
         if title:
-            print( "[ /Title ({})".format( title ), file=temp_file )
+            print( "[ /Title ({})".format( title ), file=pdfmarks_file )
         else:
-            print( "[", file=temp_file )
-        print( "  /DOCINFO pdfmark", file=temp_file )
-        print( file=temp_file )
+            print( "[", file=pdfmarks_file )
+        print( "  /DOCINFO pdfmark", file=pdfmarks_file )
+        print( file=pdfmarks_file )
         for ruleid, target in targets.items():
             xpos, ypos = target.get( "pos", ["null","null"] )
             if isinstance( ypos, int ):
@@ -50,9 +79,9 @@ def main( pdf_file, title, targets_fname, yoffset, output_fname, gs_path ):
                 raise RuntimeError( "PDF destinations cannot have spaces." )
             print( "[ /Dest /{} /Page {} /View [/XYZ {} {}] /DEST pdfmark".format(
                 ruleid, target["page_no"], xpos, ypos
-            ), file=temp_file )
-        print( file=temp_file )
-        temp_file.close( delete=False )
+            ), file=pdfmarks_file )
+        print( file=pdfmarks_file )
+        pdfmarks_file.close( delete=False )
 
         # generate the pdfmark'ed document
         print( "Generating the pdfmark'ed document..." )
@@ -60,7 +89,7 @@ def main( pdf_file, title, targets_fname, yoffset, output_fname, gs_path ):
         args = [ gs_path, "-q", "-dBATCH", "-dNOPAUSE", "-sDEVICE=pdfwrite" ]
         args.extend( [ "-o", output_fname ] )
         args.extend( [ "-f", pdf_file ] )
-        args.append( temp_file.name )
+        args.append( pdfmarks_file.name )
         start_time = time.time()
         subprocess.run( args, check=True )
         elapsed_time = time.time() - start_time