Merge pull request #6470 from radarhere/pdf_ccittfaxdecode

Save 1 mode PDF using CCITTFaxDecode filter

Author: hugovk

Tests/test_file_libtiff.py

@@ -1011,14 +1011,18 @@ def test_save_multistrip(self, compression, tmp_path):
             # Assert that there are multiple strips
             assert len(im.tag_v2[STRIPOFFSETS]) > 1
 
-    def test_save_single_strip(self, tmp_path):
+    @pytest.mark.parametrize("argument", (True, False))
+    def test_save_single_strip(self, argument, tmp_path):
         im = hopper("RGB").resize((256, 256))
         out = str(tmp_path / "temp.tif")
 
-        TiffImagePlugin.STRIP_SIZE = 2**18
+        if not argument:
+            TiffImagePlugin.STRIP_SIZE = 2**18
         try:
-
-            im.save(out, compression="tiff_adobe_deflate")
+            arguments = {"compression": "tiff_adobe_deflate"}
+            if argument:
+                arguments["strip_size"] = 2**18
+            im.save(out, **arguments)
 
             with Image.open(out) as im:
                 assert len(im.tag_v2[STRIPOFFSETS]) == 1

Tests/test_file_pdf.py

@@ -43,7 +43,7 @@ def test_monochrome(tmp_path):
 
     # Act / Assert
     outfile = helper_save_as_pdf(tmp_path, mode)
-    assert os.path.getsize(outfile) < 15000
+    assert os.path.getsize(outfile) < 5000
 
 
 def test_greyscale(tmp_path):

src/PIL/PdfImagePlugin.py

@@ -21,6 +21,7 @@
 ##
 
 import io
+import math
 import os
 import time
 
@@ -123,8 +124,26 @@ def _save(im, fp, filename, save_all=False):
             params = None
             decode = None
 
+            #
+            # Get image characteristics
+
+            width, height = im.size
+
             if im.mode == "1":
-                filter = "DCTDecode"
+                filter = "CCITTFaxDecode"
+                bits = 1
+                params = PdfParser.PdfArray(
+                    [
+                        PdfParser.PdfDict(
+                            {
+                                "K": -1,
+                                "BlackIs1": True,
+                                "Columns": width,
+                                "Rows": height,
+                            }
+                        )
+                    ]
+                )
                 colorspace = PdfParser.PdfName("DeviceGray")
                 procset = "ImageB"  # grayscale
             elif im.mode == "L":
@@ -161,6 +180,14 @@ def _save(im, fp, filename, save_all=False):
 
             if filter == "ASCIIHexDecode":
                 ImageFile._save(im, op, [("hex", (0, 0) + im.size, 0, im.mode)])
+            elif filter == "CCITTFaxDecode":
+                im.save(
+                    op,
+                    "TIFF",
+                    compression="group4",
+                    # use a single strip
+                    strip_size=math.ceil(im.width / 8) * im.height,
+                )
             elif filter == "DCTDecode":
                 Image.SAVE["JPEG"](im, op, filename)
             elif filter == "FlateDecode":
@@ -170,22 +197,24 @@ def _save(im, fp, filename, save_all=False):
             else:
                 raise ValueError(f"unsupported PDF filter ({filter})")
 
-            #
-            # Get image characteristics
-
-            width, height = im.size
+            stream = op.getvalue()
+            if filter == "CCITTFaxDecode":
+                stream = stream[8:]
+                filter = PdfParser.PdfArray([PdfParser.PdfName(filter)])
+            else:
+                filter = PdfParser.PdfName(filter)
 
             existing_pdf.write_obj(
                 image_refs[page_number],
-                stream=op.getvalue(),
+                stream=stream,
                 Type=PdfParser.PdfName("XObject"),
                 Subtype=PdfParser.PdfName("Image"),
                 Width=width,  # * 72.0 / resolution,
                 Height=height,  # * 72.0 / resolution,
-                Filter=PdfParser.PdfName(filter),
+                Filter=filter,
                 BitsPerComponent=bits,
                 Decode=decode,
-                DecodeParams=params,
+                DecodeParms=params,
                 ColorSpace=colorspace,
             )
 

src/PIL/TiffImagePlugin.py

@@ -1684,7 +1684,8 @@ def _save(im, fp, filename):
     stride = len(bits) * ((im.size[0] * bits[0] + 7) // 8)
     # aim for given strip size (64 KB by default) when using libtiff writer
     if libtiff:
-        rows_per_strip = 1 if stride == 0 else min(STRIP_SIZE // stride, im.size[1])
+        im_strip_size = encoderinfo.get("strip_size", STRIP_SIZE)
+        rows_per_strip = 1 if stride == 0 else min(im_strip_size // stride, im.size[1])
         # JPEG encoder expects multiple of 8 rows
         if compression == "jpeg":
             rows_per_strip = min(((rows_per_strip + 7) // 8) * 8, im.size[1])