Implement skipping OCR when -s is specified

Appears to be necessary to disable each state of the pipeline that is
inactive, not just initial and terminal stages of an inactive segment.
If nothing else this makes what is going on more explicit.

src/ocrpage.py

@@ -114,7 +114,7 @@ def pdf_get_pageinfo(infile, page, width_pt, height_pt):
                   '{pdfobject:1d} {pdfid:1d} {bad_dpi_w:1d} {bad_dpi_h:1d} ' +
                   '{size:>} {ratio:>}', line)
         image = r.named
-        # pdfimages calculates DPI as 0.26.0, but adds +1 to dpi_h
+        # pdfimages calculates DPI as of 0.26.0, but adds +1 to dpi_h
         # apparent bug, so calculate explicitly
         image['dpi_w'] = image['width'] / pageinfo['width_inches']
         image['dpi_h'] = image['height'] / pageinfo['height_inches']
@@ -177,6 +177,26 @@ def setup_working_directory(input_file, soft_link_name):
         pass
 
 
+ocr_required = not pageinfo['has_text'] and options.skip_text != 0
+
+
+@active_if(not ocr_required)
+@transform(setup_working_directory,
+           formatter(),
+           os.path.join(options.tmp_fld, '%04i.skip.pdf' % pageno))
+def skip_ocr(
+        input_file,
+        output_file):
+    args_pdfseparate = [
+        'pdfseparate',
+        '-f', str(pageinfo['pageno']), '-l', str(pageinfo['pageno']),
+        input_file,
+        output_file
+    ]
+    check_call(args_pdfseparate)
+
+
+@active_if(ocr_required)
 @transform(setup_working_directory,
            formatter(),
            "{path[0]}/%04i.pnm" % pageno)
@@ -239,6 +259,7 @@ def unpack_with_pdftoppm(
         raise CalledProcessError(p.returncode, args_pdftoppm)
 
 
+@active_if(ocr_required)
 @transform(unpack_with_pdftoppm, suffix(".pnm"), ".tif")
 def convert_to_tiff(input_file, output_file):
     args_convert = [
@@ -249,6 +270,7 @@ def convert_to_tiff(input_file, output_file):
     check_call(args_convert)
 
 
+@active_if(ocr_required)
 @active_if(options.preprocess_deskew != 0
            and options.deskew_provider == 'imagemagick')
 @transform(convert_to_tiff, suffix(".tif"), ".deskewed.tif")
@@ -277,6 +299,7 @@ def deskew_imagemagick(input_file, output_file):
         raise CalledProcessError(p.returncode, args_convert)
 
 
+@active_if(ocr_required)
 @active_if(options.preprocess_deskew != 0
            and options.deskew_provider == 'leptonica')
 @transform(convert_to_tiff, suffix(".tif"), ".deskewed.tif")
@@ -287,6 +310,8 @@ def deskew_leptonica(input_file, output_file):
                min(pageinfo['xres'], pageinfo['yres']))
 
 
+@active_if(ocr_required)
+@active_if(options.preprocess_clean != 0)
 @merge([unpack_with_pdftoppm, deskew_imagemagick, deskew_leptonica],
        os.path.join(options.tmp_fld, "%04i.for_clean.pnm" % pageno))
 def select_image_for_cleaning(infiles, output_file):
@@ -299,6 +324,7 @@ def select_image_for_cleaning(infiles, output_file):
     check_call(args_convert)
 
 
+@active_if(ocr_required)
 @active_if(options.preprocess_clean != 0)
 @transform(select_image_for_cleaning, suffix(".pnm"), ".cleaned.pnm")
 def clean_unpaper(input_file, output_file):
@@ -329,6 +355,7 @@ def clean_unpaper(input_file, output_file):
         raise CalledProcessError(p.returncode, args_unpaper)
 
 
+@active_if(ocr_required)
 @transform(clean_unpaper, suffix(".cleaned.pnm"), ".cleaned.tif")
 def cleaned_to_tiff(input_file, output_file):
     args_convert = [
@@ -339,6 +366,7 @@ def cleaned_to_tiff(input_file, output_file):
     check_call(args_convert)
 
 
+@active_if(ocr_required)
 @merge([convert_to_tiff, deskew_imagemagick, deskew_leptonica,
         cleaned_to_tiff],
        os.path.join(options.tmp_fld, "%04i.for_ocr.tif" % pageno))
@@ -369,6 +397,7 @@ hocr_template = '''<?xml version="1.0" encoding="UTF-8"?>
 </html>'''
 
 
+@active_if(ocr_required)
 @transform(select_ocr_image, suffix(".for_ocr.tif"), ".hocr")
 def ocr_tesseract(
         input_file,
@@ -409,6 +438,7 @@ def ocr_tesseract(
         re_symlink(output_file + ".html", output_file, logger, logger_mutex)
 
 
+@active_if(ocr_required)
 @merge([convert_to_tiff, deskew_imagemagick, deskew_leptonica,
         cleaned_to_tiff],
        os.path.join(options.tmp_fld, "%04i.image_for_pdf.tif" % pageno))
@@ -424,8 +454,9 @@ def select_image_for_pdf(infiles, output_file):
     re_symlink(input_file, output_file, logger, logger_mutex)
 
 
+@active_if(ocr_required)
 @merge([ocr_tesseract, select_image_for_pdf],
-       os.path.join(options.tmp_fld, '%04i.ocred.pdf' % pageno))
+       os.path.join(options.tmp_fld, '%04i.rendered.pdf' % pageno))
 def render_page(infiles, output_file):
     # Call python in a subprocess because:
     #  -That is python2 and this is python3
@@ -452,6 +483,12 @@ def render_page(infiles, output_file):
         raise CalledProcessError(p.returncode, args_hocrTransform)
 
 
+@merge([render_page, skip_ocr],
+       os.path.join(options.tmp_fld, '%04i.ocred.pdf' % pageno))
+def select_final_page(infiles, output_file):
+    re_symlink(infiles[-1], output_file, logger, logger_mutex)
+
+
 cmdline.run(options)
 
 # parser.add_argument(