圖片放大縮小算法——差值法

網上找一個比較簡單算法，

/*********************************

* @todo 圖片放大縮小
* @param srcImg 原始圖片
* @param desW 變化後圖片的寬
* @param desH 變化後圖片的高
* @return 處理後的圖片
*********************************/
private Image ZoomImage(Image srcImg, int desW, int desH) {
int srcW = srcImg.getWidth(); //原始圖像寬
int srcH = srcImg.getHeight(); //原始圖像高


short[] srcBuf = new short[srcW * srcH]; //原始圖片像素信息緩存


//srcBuf獲取圖片像素信息
Image desImg = Image.createImage(srcW, srcH);
if (srcImg.isMutable()) { /*如果是可變圖像*/
DirectUtils.getDirectGraphics(srcImg.getGraphics()).
getPixels(srcBuf, 0, srcW, 0, 0, srcW, srcH, 444);
} else { /*如果是非可變圖像*/
desImg.getGraphics().drawImage(srcImg, 0, 0, 0);
DirectUtils.getDirectGraphics(desImg.getGraphics()).
getPixels(srcBuf, 0, srcW, 0, 0, srcW, srcH, 444);
}


//計算插值表
short[] tabY = new short[desH];
short[] tabX = new short[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] = (short) 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++;
}
}


//生成放大縮小後圖形像素buf
short[] desBuf = new short[desW * desH];
int dx = 0;
int dy = 0;
int sx = 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;
}