[Bugfix][Regression][Server] JPEG output for WMS GetPrint request has gone

In QGIS Server 2.* the WMS GetPrint request could genrate JPEG image. QGIS Server 3.4 has lost this capabilities.
```
<ServiceExceptionReport xmlns="http://www.opengis.net/ogc" version="1.3.0" capture-installed="true">
    <ServiceException code="InvalidFormat">
        Output format jpg is not supported by the GetPrint request
    </ServiceException>
</ServiceExceptionReport>
```
To fix this regression, it is necessary to accept JPEG output format.

And to avoid this regression to come back, the QGIS Server tests has been updated to accept jpg image test.

Author: rldhont

src/server/services/wms/qgswmsgetprint.cpp

@@ -42,21 +42,29 @@ namespace QgsWms
     if ( format.compare( QLatin1String( "image/png" ), Qt::CaseInsensitive ) == 0 ||
          format.compare( QLatin1String( "png" ), Qt::CaseInsensitive ) == 0 )
     {
-      format   = "png";
-      contentType = "image/png";
+      format   = QStringLiteral( "png" );
+      contentType = QStringLiteral( "image/png" );
+    }
+    else if ( format.compare( QLatin1String( "image/jpg" ), Qt::CaseInsensitive ) == 0 ||
+              format.compare( QLatin1String( "image/jpeg" ), Qt::CaseInsensitive ) == 0 ||
+              format.compare( QLatin1String( "jpg" ), Qt::CaseInsensitive ) == 0 ||
+              format.compare( QLatin1String( "jpeg" ), Qt::CaseInsensitive ) == 0 )
+    {
+      format   = QStringLiteral( "jpg" );
+      contentType = QStringLiteral( "image/jpeg" );
     }
     else if ( format.compare( QLatin1String( "image/svg" ), Qt::CaseInsensitive ) == 0 ||
               format.compare( QLatin1String( "image/svg+xml" ), Qt::CaseInsensitive ) == 0 ||
               format.compare( QLatin1String( "svg" ), Qt::CaseInsensitive ) == 0 )
     {
-      format   = "svg";
-      contentType = "image/svg+xml";
+      format   = QStringLiteral( "svg" );
+      contentType = QStringLiteral( "image/svg+xml" );
     }
     else if ( format.compare( QLatin1String( "application/pdf" ), Qt::CaseInsensitive ) == 0 ||
               format.compare( QLatin1String( "pdf" ), Qt::CaseInsensitive ) == 0 )
     {
-      format = "pdf";
-      contentType = "application/pdf";
+      format = QStringLiteral( "pdf" );
+      contentType = QStringLiteral( "application/pdf" );
     }
     else
     {

tests/src/python/test_qgsserver.py

@@ -176,12 +176,20 @@ def _result(self, data):
 
         return data[1], headers
 
-    def _img_diff(self, image, control_image, max_diff, max_size_diff=QSize()):
-        temp_image = os.path.join(tempfile.gettempdir(), "%s_result.png" % control_image)
+    def _img_diff(self, image, control_image, max_diff, max_size_diff=QSize(), outputJpg=False):
+
+        extFile = 'png'
+        if outputJpg:
+            extFile = 'jpg'
+
+        temp_image = os.path.join(tempfile.gettempdir(), "%s_result.%s" % (control_image, extFile))
 
         with open(temp_image, "wb") as f:
             f.write(image)
 
+        if outputJpg:
+            return (True, "QgsRenderChecker can't be used for JPG images")
+
         control = QgsRenderChecker()
         control.setControlPathPrefix("qgis_server")
         control.setControlName(control_image)
@@ -190,35 +198,41 @@ def _img_diff(self, image, control_image, max_diff, max_size_diff=QSize()):
             control.setSizeTolerance(max_size_diff.width(), max_size_diff.height())
         return control.compareImages(control_image, max_diff), control.report()
 
-    def _img_diff_error(self, response, headers, image, max_diff=100, max_size_diff=QSize(), unittest_data_path='control_images'):
+    def _img_diff_error(self, response, headers, image, max_diff=100, max_size_diff=QSize(), unittest_data_path='control_images', outputJpg=False):
+
+        extFile = 'png'
+        contentType = 'image/png'
+        if outputJpg:
+            extFile = 'jpg'
+            contentType = 'image/jpeg'
 
-        reference_path = unitTestDataPath(unittest_data_path) + '/qgis_server/' + image + '/' + image + '.png'
+        reference_path = unitTestDataPath(unittest_data_path) + '/qgis_server/' + image + '/' + image + '.' + extFile
         self.store_reference(reference_path, response)
 
         self.assertEqual(
-            headers.get("Content-Type"), "image/png",
-            "Content type is wrong: %s\n%s" % (headers.get("Content-Type"), response))
+            headers.get("Content-Type"), contentType,
+            "Content type is wrong: %s instead of %s\n%s" % (headers.get("Content-Type"), contentType, response))
 
-        test, report = self._img_diff(response, image, max_diff, max_size_diff)
+        test, report = self._img_diff(response, image, max_diff, max_size_diff, outputJpg)
 
-        with open(os.path.join(tempfile.gettempdir(), image + "_result.png"), "rb") as rendered_file:
+        with open(os.path.join(tempfile.gettempdir(), image + "_result." + extFile), "rb") as rendered_file:
             encoded_rendered_file = base64.b64encode(rendered_file.read())
             if not os.environ.get('ENCODED_OUTPUT'):
-                message = "Image is wrong\: rendered file %s/%s_result.png" % (tempfile.gettempdir(), image)
+                message = "Image is wrong\: rendered file %s/%s_result.%s" % (tempfile.gettempdir(), image, extFile)
             else:
-                message = "Image is wrong\n%s\nImage:\necho '%s' | base64 -d >%s/%s_result.png" % (
-                    report, encoded_rendered_file.strip().decode('utf8'), tempfile.gettempdir(), image
+                message = "Image is wrong\n%s\nImage:\necho '%s' | base64 -d >%s/%s_result.%s" % (
+                    report, encoded_rendered_file.strip().decode('utf8'), tempfile.gettempdir(), image, extFile
                 )
 
         # If the failure is in image sizes the diff file will not exists.
-        if os.path.exists(os.path.join(tempfile.gettempdir(), image + "_result_diff.png")):
-            with open(os.path.join(tempfile.gettempdir(), image + "_result_diff.png"), "rb") as diff_file:
+        if os.path.exists(os.path.join(tempfile.gettempdir(), image + "_result_diff." + extFile)):
+            with open(os.path.join(tempfile.gettempdir(), image + "_result_diff." + extFile), "rb") as diff_file:
                 if not os.environ.get('ENCODED_OUTPUT'):
-                    message = "Image is wrong\: diff file %s/%s_result_diff.png" % (tempfile.gettempdir(), image)
+                    message = "Image is wrong\: diff file %s/%s_result_diff.%s" % (tempfile.gettempdir(), image, extFile)
                 else:
                     encoded_diff_file = base64.b64encode(diff_file.read())
-                    message += "\nDiff:\necho '%s' | base64 -d > %s/%s_result_diff.png" % (
-                        encoded_diff_file.strip().decode('utf8'), tempfile.gettempdir(), image
+                    message += "\nDiff:\necho '%s' | base64 -d > %s/%s_result_diff.%s" % (
+                        encoded_diff_file.strip().decode('utf8'), tempfile.gettempdir(), image, extFile
                     )
 
         self.assertTrue(test, message)

tests/src/python/test_qgsserver_accesscontrol.py

@@ -202,8 +202,13 @@ def _post_restricted(self, data, query_string=None):
         self._server.putenv("QGIS_PROJECT_FILE", '')
         return result
 
-    def _img_diff(self, image, control_image, max_diff, max_size_diff=QSize()):
-        temp_image = os.path.join(tempfile.gettempdir(), "%s_result.png" % control_image)
+    def _img_diff(self, image, control_image, max_diff, max_size_diff=QSize(), outputJpg=False):
+
+        extFile = 'png'
+        if outputJpg:
+            extFile = 'jpg'
+
+        temp_image = os.path.join(tempfile.gettempdir(), "%s_result.%s" % (control_image, extFile))
 
         with open(temp_image, "wb") as f:
             f.write(image)

tests/src/python/test_qgsserver_wms_getprint.py

@@ -91,6 +91,22 @@ def test_wms_getprint_basic(self):
         r, h = self._result(self._execute_request(qs))
         self._img_diff_error(r, h, "WMS_GetPrint_Basic")
 
+        # Output JPEG
+        qs = "?" + "&".join(["%s=%s" % i for i in list({
+            "MAP": urllib.parse.quote(self.projectPath),
+            "SERVICE": "WMS",
+            "VERSION": "1.1.1",
+            "REQUEST": "GetPrint",
+            "TEMPLATE": "layoutA4",
+            "FORMAT": "jpeg",
+            "map0:EXTENT": "-33626185.498,-13032965.185,33978427.737,16020257.031",
+            "LAYERS": "Country,Hello",
+            "CRS": "EPSG:3857"
+        }.items())])
+
+        r, h = self._result(self._execute_request(qs))
+        self._img_diff_error(r, h, "WMS_GetPrint_Basic", outputJpg=True)
+
     def test_wms_getprint_style(self):
         # default style
         qs = "?" + "&".join(["%s=%s" % i for i in list({