TextureHelper.java

package cpw.mods.fml.client;

import java.nio.ByteBuffer;
import java.util.List;

import net.minecraft.client.renderer.texture.Texture;
import net.minecraft.client.renderer.texture.TextureStitched;

public abstract class TextureHelper {

    /**
     * Copy the texture from the source to the atlas at the specified position
     *
     * This will use the devised GL helper to do either GL-side copy or a subimage upload
     *
     * @param atlas The atlas texture we're copying into
     * @param source The source texture we're copying from (complete)
     * @param atlasX The X position on the atlas
     * @param atlasY The Y position on the atlas
     */
    public abstract void doTextureCopy(Texture atlas, Texture source, int atlasX, int atlasY);

    /**
     * Upload the texture to the GPU for GL side copying operations
     * This may be a no-op depending on the active implementation.
     *
     * @param source The texture to upload
     */
    public abstract void doTextureUpload(TextureStitched source);

    /**
     * Rotate the texture so that it doesn't need a rotational transform applied each tick
     *
     * @param texture The texture to rotate
     * @param buffer The buffer for the texture
     */
    public void rotateTexture(Texture texture, ByteBuffer buffer)
    {
        ByteBuffer bytebuffer = buffer;
        buffer.position(0);
        ByteBuffer other = ByteBuffer.allocateDirect(buffer.capacity());
        other.position(0);

        int texHeight = texture.getHeight();
        int texWidth = texture.getWidth();

        for (int row = 0; row < texHeight; ++row)
        {
            int targCol = texHeight - row - 1;
            int srcRowOffset = row * texWidth;

            for (int col = 0; col < texWidth; ++col)
            {
                int targIndex = col * texHeight + targCol;
                int srcIndex = srcRowOffset + col;

                srcIndex <<=2;
                targIndex <<=2;

                other.put(targIndex + 0, bytebuffer.get(srcIndex + 0));
                other.put(targIndex + 1, bytebuffer.get(srcIndex + 1));
                other.put(targIndex + 2, bytebuffer.get(srcIndex + 2));
                other.put(targIndex + 3, bytebuffer.get(srcIndex + 3));
            }
        }
        buffer.position(0);
        buffer.put(other);
    }

}