TextureUnit.java

package com.javamarcher.util;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;

import org.lwjgl.opengl.GL11;
import org.lwjgl.opengl.GL13;
import org.lwjgl.opengl.GL20;
import org.lwjgl.opengl.GL30;

import de.matthiasmann.twl.utils.PNGDecoder;
import de.matthiasmann.twl.utils.PNGDecoder.Format;

public class TextureUnit {
	private final int textureId;
	private final int shaderProgramId;
	
	private int width = 0;
	private int height = 0;
	
	private ByteBuffer textureBuffer = null;
	
	public TextureUnit(String fileName, int textureUnit, int shaderProgramId, int samplerPosition, String uniformName) {
		textureId = loadTextures(fileName, textureUnit);
		this.shaderProgramId = shaderProgramId;
		linkToShader(samplerPosition, uniformName);
	}
	
	private void linkToShader(final int samplerPosition, final String uniformName) {
		GL20.glUseProgram(shaderProgramId);
		int noiseTex = GL20.glGetUniformLocation(shaderProgramId, uniformName);
		GL20.glUniform1i(noiseTex, samplerPosition);
		GL20.glUseProgram(0);
	}
	
	private int loadTextures(String filename, int textureUnit) {
		try {
		    // Open the PNG file as an InputStream
		    InputStream in = new FileInputStream(filename);
		    // Link the PNG decoder to this stream
		    PNGDecoder decoder = new PNGDecoder(in);
		     
		    // Get the width and height of the texture
		    width = decoder.getWidth();
		    height = decoder.getHeight();
		     
		    // Decode the PNG file in a ByteBuffer
		    textureBuffer = ByteBuffer.allocateDirect(4 * decoder.getWidth() * decoder.getHeight());
		    decoder.decode(textureBuffer, decoder.getWidth() * 4, Format.RGBA);
		    textureBuffer.flip();
		     
		    in.close();
		} catch (IOException e) {
		    e.printStackTrace();
		    System.exit(-1);
		}
		
		// Create a new texture object in memory and bind it
        int texId = GL11.glGenTextures();
        GL13.glActiveTexture(textureUnit);
        GL11.glBindTexture(GL11.GL_TEXTURE_2D, texId);
         
        // All RGB bytes are aligned to each other and each component is 1 byte
        GL11.glPixelStorei(GL11.GL_UNPACK_ALIGNMENT, 1);
         
        // Upload the texture data and generate mip maps (for scaling)
        GL11.glTexImage2D(GL11.GL_TEXTURE_2D, 0, GL11.GL_RGB, width, height, 0, GL11.GL_RGBA, GL11.GL_UNSIGNED_BYTE, textureBuffer);
        
        GL30.glGenerateMipmap(GL11.GL_TEXTURE_2D);
         
        // Setup the ST coordinate system
//        GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_S, GL11.GL_REPEAT);
//        GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_T, GL11.GL_REPEAT);
         
        // Setup what to do when the texture has to be scaled
        GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_MIN_FILTER, GL11.GL_LINEAR);
        GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_MAG_FILTER, GL11.GL_LINEAR);
                
        return texId;
	}

	public int getTextureId() {
		return textureId;
	}

	public int getWidth() {
		return width;
	}

	public int getHeight() {
		return height;
	}
}