[android] use native image encoding and decoding

platform/android/src/bitmap_factory.cpp

@@ -0,0 +1,25 @@
+#include "bitmap_factory.hpp"
+
+namespace mbgl {
+namespace android {
+
+void BitmapFactory::registerNative(jni::JNIEnv& env) {
+    _class = *jni::Class<BitmapFactory>::Find(env).NewGlobalRef(env).release();
+}
+
+jni::Class<BitmapFactory> BitmapFactory::_class;
+
+jni::Object<Bitmap> BitmapFactory::DecodeByteArray(jni::JNIEnv& env,
+                                                   jni::Array<jni::jbyte> data,
+                                                   jni::jint offset,
+                                                   jni::jint length) {
+
+    // Images are loaded with ARGB_8888 config, and premultiplied by default, which is exactly
+    // what we want, so we're not providing a BitmapFactory.Options object.
+    using Signature = jni::Object<Bitmap>(jni::Array<jni::jbyte>, jni::jint, jni::jint);
+    auto method = _class.GetStaticMethod<Signature>(env, "decodeByteArray");
+    return _class.Call(env, method, data, offset, length);
+}
+
+} // namespace android
+} // namespace mbgl