Affine2.java

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

import java.io.IOException;

// Affine

public class Affine2 extends MIDlet
{
  public Affine2()
    {
      Affine2Canvas c = new Affine2Canvas();
      Display.getDisplay(this).setCurrent(c);
    }

  protected void startApp() {}
  protected void pauseApp() {}
  protected void destroyApp(boolean flag) {}
}

class Affine2Canvas extends Canvas
{
  public static final int BLACK  = 0x00000000;
  public static final int YELLOW = 0x00FFFF00;
  public static final int WHITE  = 0x00FFFFFF;

  private double[] m;

  public Affine2Canvas()
    {
      super();
      this.m = new double[6];
      loadIdentity();  // 変換の初期状態は恒等変換
    }

  // 恒等変換 (何もしない変換) を設定する
  public void loadIdentity()
    {
      this.m[0] = 1.0; this.m[1] = 0.0; this.m[2] = 0.0;
      this.m[3] = 0.0; this.m[4] = 1.0; this.m[5] = 0.0;
    }

  // 変換を合成する
  public void combine(double[] mm)
    {
      double[] old = new double[6];
      for (int i = 0; i < 6; ++i) old[i] = this.m[i];

      this.m[0] = mm[0]*old[0] + mm[1]*old[3];
      this.m[1] = mm[0]*old[1] + mm[1]*old[4];
      this.m[2] = mm[0]*old[2] + mm[1]*old[5] + mm[2];

      this.m[3] = mm[3]*old[0] + mm[4]*old[3];
      this.m[4] = mm[3]*old[1] + mm[4]*old[4];
      this.m[5] = mm[3]*old[2] + mm[4]*old[5] + mm[5];
    }

  // 拡大縮小 (スケーリング)
  //
  // @param sx  magnification of the X direction (X 方向の倍率)
  // @param sy  magnification of the Y direction (Y 方向の倍率)
  public void scale(double sx, double sy)
    {
      double[] mm = new double[6];
      mm[0] = sx;  mm[1] = 0.0; mm[2] = 0.0;
      mm[3] = 0.0; mm[4] = sy;  mm[5] = 0.0;
      combine(mm);
    }

  public double transformX(double x, double y)
    {
      return this.m[0]*x + this.m[1]*y + this.m[2];
    }

  public double transformY(double x, double y)
    {
      return this.m[3]*x + this.m[4]*y + this.m[5];
    }

  protected void paint(Graphics g)
    {
      // setup a pixel data
      PixelData pixels = new PixelData(getWidth(), getHeight()); // <*>
      pixels.fillRect(0, 0, getWidth(), getHeight(), WHITE); // <*>

      // load image file
      try {
        PixelData sample_pixels = PixelData.createPixelData("/nekobean.png");

        double sx = pixels.getWidth()  / (double)sample_pixels.getWidth();
        double sy = pixels.getHeight() / (double)sample_pixels.getHeight();
        scale(sx, sy);
        
        // 画像の表示できる範囲だけを画面に描く
        for (int y = 0; y < sample_pixels.getHeight(); ++y) {
          for (int x = 0; x < sample_pixels.getWidth(); ++x) {
            // 画像の座標 (x, y) から画面の座標 (xx, yy) を求める
            int xx = (int)transformX(x, y);
            int yy = (int)transformY(x, y);
            if (0 <= xx && xx < pixels.getWidth() &&
                0 <= yy && yy < pixels.getHeight()) {
              // 描く
              int v = sample_pixels.getPixel(x, y);
              pixels.setPixel(xx, yy, v);
            }
          }
        }
      }
      catch (IOException e) {
      }

      // fill the screen black
      g.setColor(BLACK);
      g.fillRect(0, 0, getWidth(), getHeight());

      // create image from pixel data
      Image img = pixels.createRGBImage(); // <*>

      // draw image
      g.drawImage(img, 0, 0, Graphics.LEFT | Graphics.TOP);
    }
}