jsvascript图像处理―(计算机视觉应用)图像金字塔

var pyrDown = function(__src, __dst){
__src || error(arguments.callee, IS_UNDEFINED_OR_NULL/* {line} */);
if(__src.type && __src.type == "CV_RGBA"){
var width = __src.col,
height = __src.row,
dWidth = ((width & 1) + width) / 2,
dHeight = ((height & 1) + height) / 2,
sData = __src.data,
dst = __dst || new Mat(dHeight, dWidth, CV_RGBA),
dstData = dst.data;
var withBorderMat = copyMakeBorder(__src, 2, 2, 0, 0),
mData = withBorderMat.data,
mWidth = withBorderMat.col;
var newValue, nowX, offsetY, offsetI, dOffsetI, i, j;
var kernel = [1, 4, 6, 4, 1,
, 16, 24, 16, 4,
, 24, 36, 24, 6,
, 16, 24, 16, 4,
, 4, 6, 4, 1
];
for(i = dHeight; i--;){
dOffsetI = i * dWidth;
for(j = dWidth; j--;){
for(c = 3; c--;){
newValue = 0;
for(y = 5; y--;){
offsetY = (y + i * 2) * mWidth * 4;
for(x = 5; x--;){
nowX = (x + j * 2) * 4 + c;
newValue += (mData[offsetY + nowX] * kernel[y * 5 + x]);
}
}
dstData[(j + dOffsetI) * 4 + c] = newValue / 256;
}
dstData[(j + dOffsetI) * 4 + 3] = mData[offsetY + 2 * mWidth * 4 + (j * 2 + 2) * 4 + 3];
}
}
}else{
error(arguments.callee, UNSPPORT_DATA_TYPE/* {line} */);
}
return dst;
};