update MapScript map provider output formats (#2131)

* update MapScript map provider output formats

* fix syntax in docs

Author: tomkralidis

docs/source/publishing/stac.rst

@@ -153,7 +153,7 @@ So, the following rules must be respected:
 File examples
 *************
 
-**Structure of the catalog.json file**
+Structure of the ``catalog.json`` file:
 
 .. code-block:: json
 
@@ -215,7 +215,7 @@ The code above shows the root catalog. The sub-catalogs have an additional ``rel
 
 -------------------------------------
 
-**Structure of the ``collection.json`` file**
+Structure of the ``collection.json`` file:
 
 Collections are similar to Catalogs with extra fields.
 
@@ -272,7 +272,7 @@ Collections are similar to Catalogs with extra fields.
   }
 
 
-**Structure of the Item ``<id>.json`` file**
+Structure of the Item ``<id>.json`` file:
 
 The example below shows the content of a file named ``arcticdem-frontiere-0.json``:
 

pygeoapi/provider/mapscript_.py

@@ -40,10 +40,9 @@
 LOGGER = logging.getLogger(__name__)
 
 IMAGE_FORMATS = {
-    'png': 'GD/PNG',
-    'png24': 'GD/PNG24',
-    'gif': 'GD/GIF',
-    'jpeg': 'GD/JPEG'
+    'png': 'AGG/PNG',  # 24-bit by default
+    'png8': 'AGG/PNG8',
+    'jpeg': 'AGG/JPEG'
 }