Added saving LA images as PDFs

Tests/test_file_pdf.py

@@ -43,8 +43,9 @@ def test_save(tmp_path, mode):
 
 
 @skip_unless_feature("jpg_2000")
-def test_save_rgba(tmp_path):
-    helper_save_as_pdf(tmp_path, "RGBA")
+@pytest.mark.parametrize("mode", ("LA", "RGBA"))
+def test_save_alpha(tmp_path, mode):
+    helper_save_as_pdf(tmp_path, mode)
 
 
 def test_monochrome(tmp_path):
@@ -57,8 +58,8 @@ def test_monochrome(tmp_path):
 
 
 def test_unsupported_mode(tmp_path):
-    im = hopper("LA")
-    outfile = str(tmp_path / "temp_LA.pdf")
+    im = hopper("PA")
+    outfile = str(tmp_path / "temp_PA.pdf")
 
     with pytest.raises(ValueError):
         im.save(outfile)

docs/handbook/image-file-formats.rst

@@ -1486,7 +1486,7 @@ files. Different encoding methods are used, depending on the image mode.
   unavailable
 * L, RGB and CMYK mode images use JPEG encoding
 * P mode images use HEX encoding
-* RGBA mode images use JPEG2000 encoding
+* LA and RGBA mode images use JPEG2000 encoding
 
 .. _pdf-saving:
 

src/PIL/PdfImagePlugin.py

@@ -159,6 +159,11 @@ def _save(im, fp, filename, save_all=False):
                 # params = f"<< /Predictor 15 /Columns {width-2} >>"
                 colorspace = PdfParser.PdfName("DeviceGray")
                 procset = "ImageB"  # grayscale
+            elif im.mode == "LA":
+                filter = "JPXDecode"
+                # params = f"<< /Predictor 15 /Columns {width-2} >>"
+                colorspace = PdfParser.PdfName("DeviceGray")
+                procset = "ImageB"  # grayscale
             elif im.mode == "P":
                 filter = "ASCIIHexDecode"
                 palette = im.getpalette()