J2ME经验总结之图片缩放

public static Image ZoomImage(Image src, int desW, int desH) {
  Image desImg = null;
  int srcW = src.getWidth(); // 原始图像宽
  int srcH = src.getHeight(); // 原始图像高
  int[] srcBuf = new int[srcW * srcH]; // 原始图片像素信息缓存

  src.getRGB(srcBuf, 0, srcW, 0, 0, srcW, srcH);

  // 计算插值表
  int[] tabY = new int[desH];
  int[] tabX = new int[desW];

  int sb = 0;
  int db = 0;
  int tems = 0;
  int temd = 0;
  int distance = srcH > desH ? srcH : desH;
  for (int i = 0; i <= distance; i++) { /* 垂直方向 */
   tabY[db] = sb;
   tems += srcH;
   temd += desH;
   if (tems > distance) {
    tems -= distance;
    sb++;
   }
   if (temd > distance) {
    temd -= distance;
    db++;
   }
  }

  sb = 0;
  db = 0;
  tems = 0;
  temd = 0;
  distance = srcW > desW ? srcW : desW;
  for (int i = 0; i <= distance; i++) { /* 水平方向 */
   tabX[db] = (short) sb;
   tems += srcW;
   temd += desW;
   if (tems > distance) {
    tems -= distance;
    sb++;
   }
   if (temd > distance) {
    temd -= distance;
    db++;
   }
  }

  // 生成放大缩小后图形像素buf
  int[] desBuf = new int[desW * desH];
  int dx = 0;
  int dy = 0;
  int sy = 0;
  int oldy = -1;
  for (int i = 0; i < desH; i++) {
   if (oldy == tabY[i]) {
    System.arraycopy(desBuf, dy - desW, desBuf, dy, desW);
   } else {
    dx = 0;
    for (int j = 0; j < desW; j++) {
     desBuf[dy + dx] = srcBuf[sy + tabX[j]];
     dx++;
    }
    sy += (tabY[i] - oldy) * srcW;
   }
   oldy = tabY[i];
   dy += desW;
  }

  // 生成图片
  desImg = Image.createRGBImage(desBuf, desW, desH, false);
  return desImg;
}

这个函数是我以前在网上搜罗到的，且不谈效果，性能什么的。只觉得它非常好用。
用了很长时间，可惜不知道是谁。真要谢谢这位作者了。
这个函数使用了midp2.0的getRGB()函数，效率不错，基本上没什么可优化的了。
此外，下面再提供一个midp1.0下可用的缩放函数，它是使用可变图片实现的。可惜这个函数也不是我写的。
转载于kobjects。不过性能确实比较差，毕竟要画那么多点嘛，跟处理图片数据的方法是没有可比性的。

1 /* Copyright (c) 2002,2003, Stefan Haustein, Oberhausen, Rhld., Germany
    2  *
    3  * Permission is hereby granted, free of charge, to any person obtaining a copy
    4  * of this software and associated documentation files (the “Software”), to deal
    5  * in the Software without restriction, including without limitation the rights
    6  * to use, copy, modify, merge, publish, distribute, sublicense, and/or
    7  * sell copies of the Software, and to permit persons to whom the Software is
    8  * furnished to do so, subject to the following conditions:
    9  *
   10  * The  above copyright notice and this permission notice shall be included in
   11  * all copies or substantial portions of the Software.
   12  *
   13  * THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   14  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   15  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   16  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   17  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
   18  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
   19  * IN THE SOFTWARE. */
   20
   21 package org.kobjects.lcdui;
   22
   23
   24 import javax.microedition.lcdui.*;
   25
   26
   27 /** This class provides a single static method that allows to scale an image */
   28
   29
   30 public class ScaleImage {
   31
   32 /**
   33  * Creates a new, scaled version of the given image.
   34  *
   35  * @param src: The source image
   36  * @param dstW: The destination (scaled) image width
   37  * @param dstH: The destination (scaled) image height
   38  * @return Image: A new Image object with the given width and height.
   39  */
   40
   41  public static Image scaleImage (Image src, int dstW, int dstH) {
   42   int srcW = src.getWidth();
   43   int srcH = src.getHeight();
   44
   45   Image tmp = Image.createImage(dstW, srcH);
   46   Graphics g = tmp.getGraphics();
   47
   48   int delta = (srcW << 16) / dstW;
   49   int pos = delta/2;
   50
   51   for (int x = 0; x < dstW; x++) {
   52    g.setClip(x, 0, 1, srcH);
   53    g.drawImage(src, x - (pos >> 16), 0, Graphics.LEFT | Graphics.TOP);
   54    pos += delta;
   55   }
   56
   57   Image dst = Image.createImage(dstW, dstH);
   58   g = dst.getGraphics();
   59
   60   delta = (srcH << 16) / dstH;
   61   pos = delta/2;
   62
   63   for (int y = 0; y < dstH; y++) {
   64    g.setClip(0, y, dstW, 1);
   65    g.drawImage(tmp, 0, y - (pos >> 16), Graphics.LEFT | Graphics.TOP);
   66    pos += delta;
   67   }
   68
   69   return dst;
   70  }
   71
   72
   73 }

它们的使用方法都是一目了然，提供原始图片对象以及目标宽度跟高度，它就生成新的图片，在成像效果上，感觉都差不多，我觉得第一个方法更好。
在J2ME平台下，也没有必要去最求效果的极致，够用就好。再次感谢以上两个函数的作者。