图片放大缩小算法——差值法

 

/*********************************
* @todo 图片放大缩小
* @param srcImg 原始图片
* @param desW 变化后图片的宽
* @param desH 变化后图片的高
* @return 处理后的图片
*********************************/
private Image ZoomImage(Image srcImg, int desW, int desH) {
int srcW = srcImg.getWidth(); //原始图像宽
int srcH = srcImg.getHeight(); //原始图像高

short[] srcBuf = new short[srcW * srcH]; //原始图片像素信息缓存

//srcBuf获取图片像素信息
Image desImg = Image.createImage(srcW, srcH);
if (srcImg.isMutable()) { /*如果是可变图像*/
DirectUtils.getDirectGraphics(srcImg.getGraphics()).
getPixels(srcBuf, 0, srcW, 0, 0, srcW, srcH, 444);
} else { /*如果是非可变图像*/
desImg.getGraphics().drawImage(srcImg, 0, 0, 0);
DirectUtils.getDirectGraphics(desImg.getGraphics()).
getPixels(srcBuf, 0, srcW, 0, 0, srcW, srcH, 444);
}

//计算插值表
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++;
}
}

//生成放大缩小后图形像素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;

 

 

 

 

有一个超简单的办法，你可以对小图片的开头和结尾取样，然后在大图片中搜索。。。这个代码写的不够严谨，不过

byte[] smallPic=....
byte[] bigPic=...

long[] bigLongPic=把bigPic变成long类型 //转换成long可加快搜索速度

long start=ToLong(smallPic,true);
long end=ToLong(smallPic,false);
int offset=smallPic.length-16;　//保存小图片开头到结尾的取样点的偏移

for(int i=0;i<bigLongPic.length;i++){
    if(bigLongPic[i]==start && bigLongPic[i+offset]==end){ //比较取样点
         //这里再具体的比较
    }
}

private long ToLong(byte [] ba,bool start){
 long r=0;
 if(start){
 for(int i=0;i<8;i++)r|=ba[i]<<(8-i);
 }
 else{
 for(int i=ba.length-1,j=0;i>=0;i--,j++)r|=ba[i]<<(i-j);
}