From facdd138797c8ccc04b7a7467d84b02f6f4fd569 Mon Sep 17 00:00:00 2001
From: "James R. Barlow" <jim@purplerock.ca>
Date: Mon, 29 May 2017 11:42:27 -0700
Subject: [PATCH] Ghostscript: refactor image output resizing

---
 ocrmypdf/exec/ghostscript.py | 40 ++++++++++++++++--------------------
 1 file changed, 18 insertions(+), 22 deletions(-)

diff --git a/ocrmypdf/exec/ghostscript.py b/ocrmypdf/exec/ghostscript.py
index f3d58999..b73912f8 100644
--- a/ocrmypdf/exec/ghostscript.py
+++ b/ocrmypdf/exec/ghostscript.py
@@ -7,7 +7,6 @@ from shutil import copy
 from functools import lru_cache
 import re
 import sys
-from math import isclose
 from . import get_program
 from ..exceptions import SubprocessOutputError
 from PIL import Image
@@ -35,18 +34,6 @@ def _gs_error_reported(stream):
     return re.search(r'error', stream, flags=re.IGNORECASE)
 
 
-def _correct_image_size(input_fp, output_file, res, int_res, log):
-    # If the output size was reduced due to rounding DPI to an
-    # integer, resize the image to its expected size
-    input_fp.seek(0)
-    with Image.open(input_fp) as im:
-        expected_size = round(res[0] / int_res[0] * im.size[0]), \
-                        round(res[1] / int_res[1] * im.size[1])
-        log.info(im.size)
-        log.info(expected_size)
-        im.resize(expected_size).save(output_file)
-
-
 def rasterize_pdf(input_file, output_file, xres, yres, raster_device, log,
                   pageno=1):
     res = xres, yres
@@ -73,18 +60,27 @@ def rasterize_pdf(input_file, output_file, xres, yres, raster_device, log,
         else:
             log.debug(p.stdout)
 
-        if p.returncode == 0:
-            if isclose(int_res[0], res[0], abs_tol=0.1) and \
-                    isclose(int_res[1], res[1], abs_tol=0.1):
-                copy(tmp.name, output_file)
-            else:
-                # If the output size was reduced due to rounding DPI to an
-                # integer, resize the image to its expected size
-                _correct_image_size(tmp, output_file, res, int_res, log)
-        else:
+        if p.returncode != 0:
             log.error('Ghostscript rasterizing failed')
             raise SubprocessOutputError()
 
+        tmp.seek(0)
+
+        # Ghostscript only accepts integers for output resolution
+        # if the resolution happens to be fractional, then the discrepancy
+        # would change the size of the output page, especially if the DPI
+        # is quite low. Resize the image to the expected size
+        with Image.open(tmp) as im:
+            expected_size = round(im.size[0] / int_res[0] * res[0]), \
+                            round(im.size[1] / int_res[1] * res[1])
+            if expected_size != im.size:
+                log.debug(
+                    "Ghostscript: resize output image {} -> {}".format(
+                        im.size, expected_size))
+                im.resize(expected_size).save(output_file)
+            else:
+                copy(tmp.name, output_file)
+
 
 def generate_pdfa(pdf_pages, output_file, compression, log,
                   threads=1, pdf_version='1.5'):