gistfile1.java

package cojo.game.tile;

import cojo.game.render.RenderUtils;

public class TileImpl extends Tile {

	private String image;
	
	private TiledLayerObject layer;
	
	private TiledTilesetObject tileset;
	
	private int subImageIndex;
	
	public TileImpl(String image, int tileX, int tileY, TiledLayerObject layer, TiledTilesetObject tileset, Integer subImageIndex) {
		super(tileX, tileY);
		this.image = image;
		this.layer = layer;
		this.tileset = tileset;
		this.subImageIndex = subImageIndex;
	}

	@Override
	public void draw() {
		RenderUtils.bindTexture(image);

    int y = getTileY(subImageIndex - 1, tileset.getImageWidth() / tileset.getTileWidth(), tileset.getImageHeight() / tileset.getTileHeight());
		int x = getTileX(subImageIndex - 1, tileset.getImageWidth() / tileset.getTileWidth(), y);
		
		int w = tileset.getTileWidth(), h = tileset.getTileHeight();
		
    //System.out.println(String.format("x: %s, y = %s", x, y));
		//System.out.println((subImageIndex - 1) + " " + x + " " + y + " " + w + " " + h);

		RenderUtils.drawTexturedRectUV(x, y, w, h, tileset.getImageWidth(), tileset.getImageHeight());
		//RenderUtils.drawTexturedRect(0, 0, tileset.getImageWidth(), tileset.getImageHeight());
	}
	
	/**
	 * Returns a tileX for the number tile it is overall
	 * @param tileID
	 * @return
	 */
	private int getTileX(int tileID, int width, int y) {
		return tileID % width;
	}
	
	/**
	 * Returns a tileY for the number tile it is overall
	 * @param tileID
	 * @return
	 */
	private int getTileY(int tileID, int width, int height) {
		return (int) Math.floor(tileID / width);
	}

}

gistfile2.java

package cojo.game.render;

import static org.lwjgl.opengl.GL11.*;

import org.newdawn.slick.opengl.TextureLoader;
import org.newdawn.slick.util.ResourceLoader;

import cojo.game.CojoGame;

public class RenderUtils {

	/**
	 * Binds a texture from the texture map if it exists. If it does not exist, it adds it to the map, then binds it.
	 * @param name Name the image is mapped to
	 */
	public static void bindTexture(String name) {
		try {
			if (!CojoGame.textureMap.containsKey(name))
				CojoGame.textureMap.put(name, TextureLoader.getTexture("PNG", ResourceLoader.getResourceAsStream(String.format("images/%s.png", name))));

			CojoGame.textureMap.get(name).bind();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	/**
	 * Draws a rectangle using quads
	 * @param x x coordinate
	 * @param y y coordinate
	 * @param w width of the rect
	 * @param h height of the rect
	 */
	public static void drawTexturedRect(float x, float y, float w, float h) {
		glEnable(GL_TEXTURE_2D);
		glBegin(GL_QUADS);
		glTexCoord2f(1, 1);
		glVertex2f(x + w, y);
		glTexCoord2f(1, 0);
		glVertex2f(x + w, y + h);	
		glTexCoord2f(0, 0);
		glVertex2f(x, y + h);	
		glTexCoord2f(0, 1);
		glVertex2f(x, y);
		glEnd();
		glDisable(GL_TEXTURE_2D);
	}
	
	/**
	 * Draws a rectangle using quads
	 * @param x x coordinate
	 * @param y y coordinate
	 * @param w width of the rect
	 * @param h height of the rect
	 * @param textureWidth width of the texture being drawn
	 * @param textureHeight height of the texture being drawn
	 */
	public static void drawTexturedRectUV(float x, float y, float w, float h, float textureWidth, float textureHeight) {
		float mx = x*w;
		float my = y*h;
		float u1 = mx / 512;
		float v1 = my / 256;
		float u2 = (mx + w) / 512;
		float v2 = (my + h) / 256;
		glEnable(GL_TEXTURE_2D);
		glBegin(GL_QUADS);
		glTexCoord2f(u1, v1); glVertex2f(0, 0);
		glTexCoord2f(u1, v2); glVertex2f(0, h);
		glTexCoord2f(u2, v2); glVertex2f(w, h);
		glTexCoord2f(u2, v1); glVertex2f(w, 0);	
		glEnd();
		glDisable(GL_TEXTURE_2D);
	}
}