Added saving RGBA images as PDFs

Tests/test_file_pdf.py

@@ -8,7 +8,7 @@
 
 from PIL import Image, PdfParser, features
 
-from .helper import hopper, mark_if_feature_version
+from .helper import hopper, mark_if_feature_version, skip_unless_feature
 
 
 def helper_save_as_pdf(tmp_path, mode, **kwargs):
@@ -42,6 +42,11 @@ def test_save(tmp_path, mode):
     helper_save_as_pdf(tmp_path, mode)
 
 
+@skip_unless_feature("jpg_2000")
+def test_save_rgba(tmp_path):
+    helper_save_as_pdf(tmp_path, "RGBA")
+
+
 def test_monochrome(tmp_path):
     # Arrange
     mode = "1"

docs/handbook/image-file-formats.rst

@@ -1457,8 +1457,13 @@ PDF
 ^^^
 
 Pillow can write PDF (Acrobat) images. Such images are written as binary PDF 1.4
-files, using either JPEG or HEX encoding depending on the image mode (and
-whether JPEG support is available or not).
+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
+* P mode images use HEX encoding
+* RGBA mode images use JPEG2000 encoding
 
 .. _pdf-saving:
 

docs/releasenotes/9.5.0.rst

@@ -54,7 +54,7 @@ TODO
 Other Changes
 =============
 
-TODO
-^^^^
+Added support for saving PDFs in RGBA mode
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-TODO
+Using the JPXDecode filter, PDFs can now be saved in RGBA mode.

src/PIL/PdfImagePlugin.py

@@ -173,6 +173,10 @@ def _save(im, fp, filename, save_all=False):
                 filter = "DCTDecode"
                 colorspace = PdfParser.PdfName("DeviceRGB")
                 procset = "ImageC"  # color images
+            elif im.mode == "RGBA":
+                filter = "JPXDecode"
+                colorspace = PdfParser.PdfName("DeviceRGB")
+                procset = "ImageC"  # color images
             elif im.mode == "CMYK":
                 filter = "DCTDecode"
                 colorspace = PdfParser.PdfName("DeviceCMYK")
@@ -199,6 +203,8 @@ def _save(im, fp, filename, save_all=False):
                 )
             elif filter == "DCTDecode":
                 Image.SAVE["JPEG"](im, op, filename)
+            elif filter == "JPXDecode":
+                Image.SAVE["JPEG2000"](im, op, filename)
             elif filter == "FlateDecode":
                 ImageFile._save(im, op, [("zip", (0, 0) + im.size, 0, im.mode)])
             elif filter == "RunLengthDecode":

src/libImaging/Jpeg2KEncode.c

@@ -487,6 +487,10 @@ j2k_encode_entry(Imaging im, ImagingCodecState state) {
         goto quick_exit;
     }
 
+    if (strcmp(im->mode, "RGBA") == 0) {
+        image->comps[3].alpha = 1;
+    }
+
     opj_set_error_handler(codec, j2k_error, context);
     opj_set_info_handler(codec, j2k_warn, context);
     opj_set_warning_handler(codec, j2k_warn, context);