[core, ios, macos] Add image accessor to MGLStyle (#7096)

* [core] Add interface to get image from sprite atlas

* [tests] Add tests for Map::getImage

* [ios, macos] WIP: get MGLImage for name from style

* [ios, macos] Fixed -imageForName:

Convert from sprite images to platform images using the existing encodePNG() function, which is also used for printing. Allow -imageForName: to return nil without an assertion failure. Added a basic test.

2 files changed, 12 insertions, 0 deletions

diff --git a/test/fixtures/map/get_icon/expected.png b/test/fixtures/map/get_icon/expected.png
new file mode 100644
index 0000000000..b112096c18
--- /dev/null
+++ b/test/fixtures/map/get_icon/expected.png
diff --git a/test/map/map.test.cpp b/test/map/map.test.cpp
index 97a09e94a0..ac82bbacae 100644
--- a/test/map/map.test.cpp
+++ b/test/map/map.test.cpp
@@ -394,3 +394,15 @@ TEST(Map, RemoveImage) {
     map.removeImage("test-icon");
     test::checkImage("test/fixtures/map/remove_icon", test::render(map, test.view));
 }
+
+TEST(Map, GetImage) {
+    MapTest test;
+
+    Map map(test.backend, test.view.size, 1, test.fileSource, test.threadPool, MapMode::Still);
+    auto decoded = decodeImage(util::read_file("test/fixtures/sprites/default_marker.png"));
+    auto image = std::make_unique<SpriteImage>(std::move(decoded), 1.0);
+
+    map.setStyleJSON(util::read_file("test/fixtures/api/icon_style.json"));
+    map.addImage("test-icon", std::move(image));
+    test::checkImage("test/fixtures/map/get_icon", map.getImage("test-icon")->image);
+}