Question

I have an app that I’ve been repeatedly playing with in android, it uses opengl-es.

Currently I load textures from a bitmap like so:

//Load up and flip the texture - then dispose the temp
    Bitmap temp = BitmapFactory.decodeResource(Deflecticon.getContext().getResources(), resourceID);
    Bitmap bmp = Bitmap.createBitmap(temp, 0, 0, temp.getWidth(), temp.getHeight(), flip, true);
    temp.recycle();

    //Bind the texture in memory
    gl.glBindTexture(GL10.GL_TEXTURE_2D, id);

    //Set the parameters of the texture.
    gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_LINEAR);
    gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);

    //On to the GPU
    GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bmp, 0);

The obvious issue is that the texture I’m using has to be a power of 2. At the moment I’m pre-editing the textures in photoshop to be a power of 2 and simply have empty borders. However this is a little tedious and I want to be able to load them as they are .. recognise they aren’t a power of 2 and load them into a texture that is.

I know I could scale the bitmap to become a power of 2 size and simply stretch the texture but I do not wish to stretch the texture and in some cases may want to put several textures into one “atlas”.

I know I can use glTexSubImage2D() to paste into the texture the data I want at the origin I want. This is great!

However I do not know how in Android to initialise a texture with no data?

In this question previously asked the suggestion was to call glTexImage2D() with no data and to then fill it.

However in android when you call “GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bmp, 0);” you do not specify a width / height. It reads this from the bitmap I assume.

What is the best way to do this? Can I create a new bitmap of the right power of 2 size only blank and not filled with any data and use this to initialise the texture then paste into it using subImage? Or should I make a new bitmap somehow copy the pixels I want (not sure if you can do this easily) into this new bitmap (leaving borders) and then just use this?

Edit: clarified that I’m using opengl.

Answer 1

I think if you tried creating a bitmap with the power of 2 axis sizes and then add your bitmap it should work just fine. maybe something like

Bitmap.createBitmap(notPowerOf2Bitmap, offx, offy, xsize, ysize, bitmapFlag)

other than that, I would say suffer through the photoshop process. How many pictures you got?