CODEWITHSUNDEEP
javapngtextureslwjgl
CosmicKidd
CosmicKidd

Reputation: 75

LWJGL: Getting Texture from .png with multiple textures

I am making a game with LWJGL and by using openGL, I believe my best option is to use Textures and render them with quads. However, I can only seem to find information on loading a texture from an image where the entire image is only ONE texture. What I would like to do is read an entire spritesheet in and be able to separate it into different textures. Is there a somewhat simple way to do this?

Upvotes: 1

Views: 1112

Answers (1)

Tanix
Tanix

Reputation: 106

You could load the image, from e.g. a .png file to a BufferedImage with

public static BufferedImage loadImage(String location)
{
    try {
        BufferedImage image = ImageIO.read(new File(location));
        return image;
    } catch (IOException e) {
        System.out.println("Could not load texture: " + location);
    }
    return null;
}

Now you are able to call getSubimage(int x, int y, int w, int h) on that resulting BufferedImage, giving you the seperated part. You now just need to create a Texture of the BufferedImage. This code should do the work:

public static int loadTexture(BufferedImage image){
    if (image == null) {
        return 0;
    }

    int[] pixels = new int[image.getWidth() * image.getHeight()];
    image.getRGB(0, 0, image.getWidth(), image.getHeight(), pixels, 0, image.getWidth());

    ByteBuffer buffer = BufferUtils.createByteBuffer(image.getWidth() * image.getHeight() * BYTES_PER_PIXEL); //4 for RGBA, 3 for RGB

    for(int y = 0; y < image.getHeight(); y++){
        for(int x = 0; x < image.getWidth(); x++){
            int pixel = pixels[y * image.getWidth() + x];
            buffer.put((byte) ((pixel >> 16) & 0xFF));     // Red component
            buffer.put((byte) ((pixel >> 8) & 0xFF));      // Green component
            buffer.put((byte) (pixel & 0xFF));               // Blue component
            buffer.put((byte) ((pixel >> 24) & 0xFF));    // Alpha component. Only for RGBA
        }
    }

    buffer.flip(); //FOR THE LOVE OF GOD DO NOT FORGET THIS

     // You now have a ByteBuffer filled with the color data of each pixel.
    // Now just create a texture ID and bind it. Then you can load it using 
    // whatever OpenGL method you want, for example:

    int textureID = glGenTextures();
    glBindTexture(GL_TEXTURE_2D, textureID);

    //setup wrap mode
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL12.GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL12.GL_CLAMP_TO_EDGE);

    //setup texture scaling filtering
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

    //Send texel data to OpenGL
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, image.getWidth(), image.getHeight(), 0, GL_RGBA, GL_UNSIGNED_BYTE, buffer); //GL_RGBA8 was GL_RGB8A

    return textureID;
}

You are now able to bind the returned textureID with glBindTexture(GL_TEXTURE_2D, textureID); if you need the texture. This way you only have to split the BufferedImage in the desired parts.

I recommend reading this: LWJGL Textures and Strings

Upvotes: 1

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