[core] Fix image type of Map::renderStill

It's a premultiplied image. This implies that we were misusing encodePNG
in most cases, as we were passing premultiplied pixels which were then
interpreted as unmultiplied. I changed encodePNG to accept premultipled
pixels, and unpremultiply in the implementations.

2 files changed, 2 insertions, 2 deletions

diff --git a/include/mbgl/map/map.hpp b/include/mbgl/map/map.hpp
index 80b50c2fa4..35895660f2 100644
--- a/include/mbgl/map/map.hpp
+++ b/include/mbgl/map/map.hpp
@@ -58,7 +58,7 @@ public:
 
     // Register a callback that will get called (on the render thread) when all resources have
     // been loaded and a complete render occurs.
-    using StillImageCallback = std::function<void (std::exception_ptr, UnassociatedImage&&)>;
+    using StillImageCallback = std::function<void (std::exception_ptr, PremultipliedImage&&)>;
     void renderStill(StillImageCallback callback);
 
     // Triggers a synchronous render.
diff --git a/include/mbgl/map/view.hpp b/include/mbgl/map/view.hpp
index 68bde5fe30..ecdd93377f 100644
--- a/include/mbgl/map/view.hpp
+++ b/include/mbgl/map/view.hpp
@@ -70,7 +70,7 @@ public:
 
     // Reads the pixel data from the current framebuffer. If your View implementation
     // doesn't support reading from the framebuffer, return a null pointer.
-    virtual UnassociatedImage readStillImage();
+    virtual PremultipliedImage readStillImage();
 
     // Notifies a watcher of map x/y/scale/rotation changes.
     // Must only be called from the same thread that caused the change.