Added PDF 2d-resolution export

Tests/test_file_pdf.py

@@ -64,6 +64,10 @@ class TestFilePdf(PillowTestCase):
         # Act / Assert
         self.helper_save_as_pdf(mode)
 
+    def test_resolution(self):
+        self.helper_save_as_pdf("RGB", resolution=300.5)
+        self.helper_save_as_pdf("RGB", resolution=(300, 150))
+
     def test_unsupported_mode(self):
         im = hopper("LA")
         outfile = self.tempfile("temp_LA.pdf")

docs/handbook/image-file-formats.rst

@@ -1054,9 +1054,9 @@ The :py:meth:`~PIL.Image.Image.save` method can take the following keyword argum
     .. versionadded:: 5.1.0
 
 **resolution**
-    Image resolution in DPI. This, together with the number of pixels in the
-    image, will determine the physical dimensions of the page that will be
-    saved in the PDF.
+    Image resolution in DPI either as a numeric value or ``(xdpi, ydpi)`` tuple.
+    This, together with the number of pixels in the image, will determine the
+    physical dimensions of the page that will be saved in the PDF.
 
 **title**
     The document’s title. If not appending to an existing PDF file, this will

src/PIL/PdfImagePlugin.py

@@ -56,6 +56,13 @@ def _save(im, fp, filename, save_all=False):
         existing_pdf = PdfParser.PdfParser(f=fp, filename=filename, mode="w+b")
 
     resolution = im.encoderinfo.get("resolution", 72.0)
+    # Allows the user to specify either a 1D resolution or 2D resolution.
+    if not isinstance(resolution, (list, tuple)):
+        pdf_width_res = resolution
+        pdf_height_res = resolution
+    else:
+        pdf_width_res = resolution[0]
+        pdf_height_res = resolution[1]
 
     info = {
         "title": None if is_appending else os.path.splitext(
@@ -211,8 +218,8 @@ def _save(im, fp, filename, save_all=False):
                                     MediaBox=[
                                         0,
                                         0,
-                                        int(width * 72.0 / resolution),
-                                        int(height * 72.0 / resolution)
+                                        int(width * 72.0 / pdf_width_res),
+                                        int(height * 72.0 / pdf_height_res)
                                     ],
                                     Contents=contents_refs[pageNumber])
 
@@ -221,8 +228,8 @@ def _save(im, fp, filename, save_all=False):
 
             page_contents = PdfParser.make_bytes(
                 "q %d 0 0 %d 0 0 cm /image Do Q\n" % (
-                    int(width * 72.0 / resolution),
-                    int(height * 72.0 / resolution)))
+                    int(width * 72.0 / pdf_width_res),
+                    int(height * 72.0 / pdf_height_res)))
 
             existing_pdf.write_obj(contents_refs[pageNumber],
                                    stream=page_contents)