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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/control/forms/event.py

@@ -231,7 +231,7 @@ class EventWizardBasicsForm(I18nModelForm):
             raise ValidationError({
                 'timezone': _('Your default locale must be specified.')
             })
-        if not data.get("no_taxes") and data.get("tax_rate") is None:
+        if not data.get("no_taxes") and not data.get("tax_rate"):
             raise ValidationError({
                 'tax_rate': _('You have not specified a tax rate. If you do not want us to compute sales taxes, please '
                               'check "{field}" above.').format(field=self.fields["no_taxes"].label)

src/pretix/control/views/main.py

@@ -313,7 +313,7 @@ class EventWizard(SafeSessionWizardView):
                     )
                 event.set_defaults()
 
-            if basics_data['tax_rate'] is not None:
+            if basics_data['tax_rate']:
                 if not event.settings.tax_rate_default or event.settings.tax_rate_default.rate != basics_data['tax_rate']:
                     event.settings.tax_rate_default = event.tax_rules.create(
                         name=LazyI18nString.from_gettext(gettext('VAT')),

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