Use DCTDecode and SMask when saving LA and RGBA PDF images

Tests/test_file_pdf.py

@@ -12,7 +12,7 @@
 
 from PIL import Image, PdfParser, features
 
-from .helper import hopper, mark_if_feature_version, skip_unless_feature
+from .helper import hopper, mark_if_feature_version
 
 
 def helper_save_as_pdf(tmp_path: Path, mode: str, **kwargs: Any) -> str:
@@ -41,17 +41,11 @@ def helper_save_as_pdf(tmp_path: Path, mode: str, **kwargs: Any) -> str:
  return outfile
 
 
-@pytest.mark.parametrize("mode", ("L", "P", "RGB", "CMYK"))
+@pytest.mark.parametrize("mode", ("L", "LA", "P", "RGB", "RGBA", "CMYK"))
 def test_save(tmp_path: Path, mode: str) -> None:
  helper_save_as_pdf(tmp_path, mode)
 
 
-@skip_unless_feature("jpg_2000")
-@pytest.mark.parametrize("mode", ("LA", "RGBA"))
-def test_save_alpha(tmp_path: Path, mode: str) -> None:
- helper_save_as_pdf(tmp_path, mode)
-
-
 def test_p_alpha(tmp_path: Path) -> None:
  # Arrange
  outfile = str(tmp_path / "temp.pdf")

docs/handbook/image-file-formats.rst

@@ -1585,9 +1585,8 @@ files. Different encoding methods are used, depending on the image mode.
 
 * 1 mode images are saved using TIFF encoding, or JPEG encoding if libtiff support is
  unavailable
-* L, RGB and CMYK mode images use JPEG encoding
+* L, LA, RGB, RGBA and CMYK mode images use JPEG encoding
 * P mode images use HEX encoding
-* LA and RGBA mode images use JPEG2000 encoding
 
 .. _pdf-saving:
 

src/PIL/PdfImagePlugin.py

@@ -54,6 +54,7 @@ def _write_image(im, filename, existing_pdf, image_refs):
 
  params = None
  decode = None
+ smask = None
 
  #
  # Get image characteristics
@@ -81,16 +82,16 @@ def _write_image(im, filename, existing_pdf, image_refs):
  filter = "DCTDecode"
  dict_obj["ColorSpace"] = PdfParser.PdfName("DeviceGray")
  procset = "ImageB" # grayscale
- elif im.mode == "L":
+ elif im.mode in ("L", "LA"):
  filter = "DCTDecode"
  # params = f"<< /Predictor 15 /Columns {width-2} >>"
  dict_obj["ColorSpace"] = PdfParser.PdfName("DeviceGray")
  procset = "ImageB" # grayscale
- elif im.mode == "LA":
- filter = "JPXDecode"
- # params = f"<< /Predictor 15 /Columns {width-2} >>"
- procset = "ImageB" # grayscale
- dict_obj["SMaskInData"] = 1
+  if im.mode == "LA":
+  smask = im
+
+  im = im.convert("L")
+  im.encoderinfo = {}
  elif im.mode == "P":
  filter = "ASCIIHexDecode"
  palette = im.getpalette()
@@ -103,19 +104,16 @@ def _write_image(im, filename, existing_pdf, image_refs):
  procset = "ImageI" # indexed color
 
  if "transparency" in im.info:
- smask = im.convert("LA").getchannel("A")
- smask.encoderinfo = {}
-
- image_ref = _write_image(smask, filename, existing_pdf, image_refs)[0]
- dict_obj["SMask"] = image_ref
- elif im.mode == "RGB":
+ smask = im.convert("LA")
+ elif im.mode in ("RGB", "RGBA"):
  filter = "DCTDecode"
  dict_obj["ColorSpace"] = PdfParser.PdfName("DeviceRGB")
  procset = "ImageC" # color images
- elif im.mode == "RGBA":
- filter = "JPXDecode"
- procset = "ImageC" # color images
- dict_obj["SMaskInData"] = 1
+ if im.mode == "RGBA":
+ smask = im
+
+ im = im.convert("RGB")
+ im.encoderinfo = {}
  elif im.mode == "CMYK":
  filter = "DCTDecode"
  dict_obj["ColorSpace"] = PdfParser.PdfName("DeviceCMYK")
@@ -125,6 +123,13 @@ def _write_image(im, filename, existing_pdf, image_refs):
  msg = f"cannot save mode {im.mode}"
  raise ValueError(msg)
 
+ if smask:
+ smask = smask.getchannel("A")
+ smask.encoderinfo = {}
+
+ image_ref = _write_image(smask, filename, existing_pdf, image_refs)[0]
+ dict_obj["SMask"] = image_ref
+
  #
  # image
 
@@ -142,9 +147,6 @@ def _write_image(im, filename, existing_pdf, image_refs):
  )
  elif filter == "DCTDecode":
  Image.SAVE["JPEG"](im, op, filename)
- elif filter == "JPXDecode":
- del dict_obj["BitsPerComponent"]
- Image.SAVE["JPEG2000"](im, op, filename)
  else:
  msg = f"unsupported PDF filter ({filter})"
  raise ValueError(msg)
@@ -236,7 +238,9 @@ def _save(im, fp, filename, save_all=False):
  number_of_pages += im_number_of_pages
  for i in range(im_number_of_pages):
  image_refs.append(existing_pdf.next_object_id(0))
- if im.mode == "P" and "transparency" in im.info:
+ if im.mode in ("LA", "RGBA") or (
+ im.mode == "P" and "transparency" in im.info
+ ):
  image_refs.append(existing_pdf.next_object_id(0))
 
  page_refs.append(existing_pdf.next_object_id(0))