旋转不变LBP特征-matlab

不断的旋转圆形邻域内的LBP特征，根据选择得到一系列的LBP特征值，从这些LBP特征值选择LBP特征值最小的作为中心像素点的LBP特征。

---

matlab源码

function imglbp = getRotationInvariantLBPFeature(img, radius, neighbors)
    imgSize = size(img);
    if numel(imgSize) > 2
        imgG = rgb2gray(img);
    else
        imgG = img;
    end
    [rows, cols] = size(imgG);
    rows=int16(rows);
    cols=int16(cols);
    imglbp = uint8(zeros(rows-2*radius, cols-2*radius));

    for k=0:neighbors-1
%       计算采样点对于中心点坐标的偏移量rx，ry        
        rx = radius * cos(2.0 * pi * k / neighbors);
        ry = -radius * sin(2.0 * pi * k / neighbors);
%       对采样点偏移量分别进行上下取整        
        x1 = floor(rx);
        x2 = ceil(rx);
        y1 = floor(ry);
        y2 = ceil(ry);
%       将坐标偏移量映射到0-1之间        
        tx = rx - x1;
        ty = ry - y1;
%       根据0-1之间的x，y的权重计算公式计算权重，权重与坐标具体位置无关，与坐标间的差值有关
        w1 = (1-tx) * (1-ty);
        w2 = tx * (1-ty);
        w3 = (1-tx) * ty;
        w4 = tx * ty;

        for i=radius+1:rows-radius
            for j=radius+1:cols-radius
                center = imgG(i, j);
%               根据双线性插值公式计算第k个采样点的灰度值                
                neighbor = imgG(i+x1, j+y1)*w1 + imgG(i+x1, j+y2)*w2 + imgG(i+x2, j+y1)*w3 + imgG(i+x2, j+y2)*w4;
%               LBP特征图像的每个邻居的LBP值累加，累加通过与操作完成，对应的LBP值通过移位取得
                if neighbor > center
                    flag = 1;
                else
                    flag = 0;
                end
                imglbp(i-radius, j-radius) = bitor(imglbp(i-radius, j-radius), bitshift(flag, neighbors-k-1));
            end
        end
    end

    for i=1:rows-2*radius
        for j=1:cols-2*radius
            currentValue = imglbp(i, j);
            minValue = currentValue;
            currentValue = dec2bin(currentValue);
 %          循环右移
            for k=1:neighbors
                temp = circshift(currentValue, k);
                temp = bin2dec(temp);

                if temp < minValue
                    minValue = temp;
                end
            end
            imglbp(i, j) = minValue;
        end
    end
end

---

效果图

原图

radius=3，neighbors=8