How do I load an image for use as an openGL texture with LWJGL?

Question

I am trying to load an image as a texture for openGL using the LWJGL library. From what I found out so far, I need to pass the texture as a ByteBuffer to openGL. What I have right now is some code that correctly loads an image, and stores it in a BufferedImage object. The thing is, I have no clue how to get from a BufferedImage to a ByteBuffer that contains data in the right format for use with openGL (as input for the function GL11.glTexImage2D()). Help is greatly appreciated!

Answer 1

Here's a method from the Space Invaders example that does what you want. (I think)

/**
 * Convert the buffered image to a texture
 */
private ByteBuffer convertImageData(BufferedImage bufferedImage) {
    ByteBuffer imageBuffer;
    WritableRaster raster;
    BufferedImage texImage;

    ColorModel glAlphaColorModel = new ComponentColorModel(ColorSpace
            .getInstance(ColorSpace.CS_sRGB), new int[] { 8, 8, 8, 8 },
            true, false, Transparency.TRANSLUCENT, DataBuffer.TYPE_BYTE);

    raster = Raster.createInterleavedRaster(DataBuffer.TYPE_BYTE,
            bufferedImage.getWidth(), bufferedImage.getHeight(), 4, null);
    texImage = new BufferedImage(glAlphaColorModel, raster, true,
            new Hashtable());

    // copy the source image into the produced image
    Graphics g = texImage.getGraphics();
    g.setColor(new Color(0f, 0f, 0f, 0f));
    g.fillRect(0, 0, 256, 256);
    g.drawImage(bufferedImage, 0, 0, null);

    // build a byte buffer from the temporary image
    // that be used by OpenGL to produce a texture.
    byte[] data = ((DataBufferByte) texImage.getRaster().getDataBuffer())
            .getData();

    imageBuffer = ByteBuffer.allocateDirect(data.length);
    imageBuffer.order(ByteOrder.nativeOrder());
    imageBuffer.put(data, 0, data.length);
    imageBuffer.flip();

    return imageBuffer;
}

Answer 2

I used the solution above by Ron but the colors of the image when applied as a texture were incorrect, which means, the accepted solution will probably not produce same results for all kinds of images.

Trying to fix the problem with the color, I tried to use the ColorModel of the original BufferedImage, which can be accessed by calling the BufferedImage#getColorModel. But, it gave me an exception that the ColorModel of the original image is incompatible with the WritableRaster object.

I looked for a solution for this and I found this one. Instead of calling Raster.createInterleavedRaster to create a WritableRaster, I used ColorModel#createCompatibleWritableRaster.

Hope this helps. Here's the code:

public static ByteBuffer load(BufferedImage bufferedImage) {

    WritableRaster raster = bufferedImage.getColorModel().createCompatibleWritableRaster
        (bufferedImage.getWidth(), bufferedImage.getHeight());
    BufferedImage textureImage = new BufferedImage(bufferedImage.getColorModel(), raster,
        true, new Hashtable<>());

    Graphics graphics = textureImage.getGraphics();
    graphics.setColor(new Color(0, 0, 0));
    graphics.fillRect(0, 0, 256, 256);
    graphics.drawImage(bufferedImage, 0, 0, null);

    byte[] data = ((DataBufferByte) textureImage.getRaster().getDataBuffer()).getData();

    ByteBuffer imageBuffer = ByteBuffer.allocate(data.length);
    imageBuffer.order(ByteOrder.nativeOrder());
    imageBuffer.put(data, 0, data.length);
    imageBuffer.flip();

    return imageBuffer;
}

Answer 3

public static ByteBuffer imageToBuffer(BufferedImage image) {
    int[] pixels = image.getRGB(0, 0, image.getWidth(), image.getHeight(), null, 0, image.getWidth());
    ByteBuffer buffer = ByteBuffer.allocateDirect(pixels.length * 4);
    for (int pixel : pixels) {
        buffer.put((byte) ((pixel >> 16) & 0xFF));
        buffer.put((byte) ((pixel >> 8) & 0xFF));
        buffer.put((byte) (pixel & 0xFF));
        buffer.put((byte) (pixel >> 24));
    }
    buffer.flip();
    return buffer;
}

Worked for me.

Answer 4

We also can do it in Shader.

BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);

DataBufferInt dbb = (DataBufferInt) image.getRaster().getDataBuffer();
glBindTexture(GL_TEXTURE_2D, id);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0,   GL_RGBA,   GL_UNSIGNED_INT_8_8_8_8,dbb.getData());

GL_FRAGMENT_SHADER:

#version 130

uniform sampler2D tex;

in vec2 texCoordsVarying;
out vec4 color;

void main() {
  vec4 c2 = texture(tex, texCoordsVarying);
  color = vec4(c2.g, c2.b, c2.a, c2.r);
}

The method given by @Displee , uses CPU time, If you just load texture once it is OK. If you update the texture every frame, you could use Shader, it use GPU and less time(1/4 time I tested on my PC)