PNG Texture OpenGL es 2.0 Android NDK

Question

I'm developing a game, actually my first game, so I'm new in this world, I'm using OpenGL with NDK and C++ for the render part, and I call it from java with JNI. I'm stuck with the textures topic, since I need to use PNG with alpha channel and use TTF for some text.

I can include the libpng, but since I'm using the experimental gradle puglin, I don't know how to add the library and use it, I saw that the library can be precompiled and be added, but from what I saw, only for one architecture, then, I don't know if I'm wrong, but I think if I add the source code of the library and compile it with the program, I think, it will be compiled for the architectures that I need (MIPS, 64-bit ARM, x86, 64-bit x86, ARM), so that is one, I was thinking in pre-convert the png in raw RGBA and use that vector directly with opengl but again, I dont know how to do this.

and with the TTF issue, well I am in blank, if you have any advice for this I would greatly appreciate it.

Thanks for your help.

Answer 1

You can build the whole FreeType engine into your code, or you can just use what's already part of Android: use Canvas to render glyphs to a Bitmap. You can find an example of this in Android Breakout . The game is written in Java rather than C++, but the Java-language GLES code is just a thin wrapper around the native stuff, so it's pretty similar.

There's a pretty good blog post about GLES text on Android here .

On a similar note, you already have a copy of libpng in your app. You can call through the Bitmap API to use it.

If you have as a goal the creation of an entirely self-contained native app, then the approach of calling into Canvas/Bitmap isn't viable. I don't think that's a particularly useful goal, however. You're better off separating the "game engine" from the game logic, eg have platform-specific "decode PNG" and "pass this pile of RGBA pixels into glTexImage2D() " functions, and platform-agnostic "use texture N".

Taking that one step further, your best approach is to use an existing graphics engine or game engine, and focus on creating the game rather than writing the engine. Learning about engines by writing one is a worthwhile endeavor, but if your actual goal is to write a game then you should focus on the game itself.