Invoice rendering: Remove transparency from logos (Z#23179391) (#4762)

* Invoice rendering: Remove logos from transparency

* Add comment

src/pretix/base/invoice.py

@@ -388,6 +388,15 @@ class ClassicInvoiceRenderer(BaseReportlabInvoiceRenderer):
             except:
                 logger.exception("Can not resize image")
                 pass
+            try:
+                # Valid ZUGFeRD invoices must be compliant with PDF/A-3. pretix-zugferd ensures this by passing them
+                # through ghost script. Unfortunately, if the logo contains transparency, this will still fail.
+                # I was unable to figure out a way to fix this in GhostScript, so the easy fix is to remove the
+                # transparency, as our invoices always have a white background anyways.
+                ir.remove_transparency()
+            except:
+                logger.exception("Can not remove transparency from logo")
+                pass
             canvas.drawImage(ir,
                              self.logo_left,
                              self.pagesize[1] - self.logo_height - self.logo_top,

src/pretix/helpers/reportlab.py

@@ -39,6 +39,12 @@ class ThumbnailingImageReader(ImageReader):
         self._data = None
         return width, height
 
+    def remove_transparency(self, background_color="WHITE"):
+        if "A" in self._image.mode:
+            new_image = Image.new("RGBA", self._image.size, background_color)
+            new_image.paste(self._image, mask=self._image)
+            self._image = new_image.convert("RGB")
+
     def _jpeg_fh(self):
         # Bypass a reportlab-internal optimization that falls back to the original
         # file handle if the file is a JPEG, and therefore does not respect the