gltest.scala

import org.lwjgl.{ BufferUtils, opengl }
import opengl.{ Display, DisplayMode, GL11 }
import GL11._

import java.nio.FloatBuffer

/*class BasicApplet {
  val serialVersionUID = 1L;
  def init() {
    //setSize(16*17*3, 16*17*3);
  }

  def paint(g: Graphics) {
    //setBackground(Color.WHITE)
  }

  }
}*/

object Main extends Application {
  val size = 1000
  Display.setDisplayMode(new DisplayMode(size,size))
  Display.create()

  glMatrixMode(GL_PROJECTION)
  glLoadIdentity()
  glOrtho(0, size, 0, size, 1, -1)
  glMatrixMode(GL_MODELVIEW)

  val texture = glGenTextures()
  val buffer = BufferUtils.createByteBuffer(0x10000 * 3)

  @inline final def clamp(f: Float) = if(f<0F) 0F else { if (f>1F) 1F else f }

  val kr = 0.2126f
  val kb = 0.0722f

  for {
    t <- 0 until 16
    s <- 0 until 16
    cb <- 0 until 16
    cr <- 0 until 16
  } { 
    val tf = t / 15f
    val sf = s / 15f
    val cbf = cb / 15f - .5f
    val crf = cr / 15f - .5f

    val y = clamp(sf + tf)

    val cb2 = (-0.003f * sf + cbf * tf) / (sf + tf)
    val cr2 = ( 0.003f * sf + crf * tf) / (sf + tf)

    val b = y + 2f * (1f - kb) * cb2
    val r = y + 2f * (1f - kr) * cr2

    val g = (y - kr * r - kb * b) / (1f - kr - kb)

    val idx = (t * 0x1000 + s * 0x10 + cb * 0x100 + cr * 0x1) * 3

    buffer.put(idx,     (clamp(r) * 255).toByte)
    buffer.put(idx + 1, (clamp(g) * 255).toByte)
    buffer.put(idx + 2, (clamp(b) * 255).toByte)
  }

  glEnable(GL_TEXTURE_2D)
  glBindTexture(GL_TEXTURE_2D, texture)
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8, 0x100, 0x100, 0, GL_RGB, GL_UNSIGNED_BYTE, buffer)

  while (!Display.isCloseRequested) {

    glClear(GL_COLOR_BUFFER_BIT)
    glBindTexture(GL_TEXTURE_2D, texture)

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST)
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST)

    glBegin(GL_QUADS); {
      glTexCoord2f(0, 0); glVertex2f(0,    0   )
      glTexCoord2f(1, 0); glVertex2f(size, 0   )
      glTexCoord2f(1, 1); glVertex2f(size, size)
      glTexCoord2f(0, 1); glVertex2f(0,    size)
    }
    glEnd()

    Display.update()
  }
  Display.destroy()
}