HOG Matlab实现

来源：互联网发布：阿里云防止ddos攻击编辑：程序博客网时间：2024/06/06 18:18

看SURF结果把HOG看的太细了 都是学习 就记一下HOG的matlab实现  方便以后学习

function [gMag,gDir] = computeGradient(img)    gx = zeros(size(img),class(img));    gy = zeros(size(img),class(img));        gx(:,2:end-1) = conv2(img, [1 0 -1], 'valid');    gy(2:end-1,:) = conv2(img, [1;0;-1], 'valid');        % forward difference on borders    gx(:,1)   = img(:,2)   - img(:,1);    gx(:,end) = img(:,end) - img(:,end-1);        gy(1,:)   = img(2,:)   - img(1,:);    gy(end,:) = img(end,:) - img(end-1,:);% return magnitude and directiongMag = hypot(gx,gy);gDir = atan2d(-gy,gx);

hypot是matlab自带的一个函数看解释

%HYPOT   Robust computation of the square root of the sum of squares%   C = HYPOT(A,B) returns SQRT(ABS(A).^2+ABS(B).^2) carefully computed to%   avoid underflow and overflow.%%   Example:%      format short e%      a = 3*[1e300 1e-300]%      b = 4*[1e300 1e-300]%      c1 = sqrt(a.^2 + b.^2)%      c2 = hypot(a,b)%%      x = 1.271161e308%      y = hypot(x,x)%%   Class support for inputs A, B:%      float: double, single%%   See also ABS, NORM, SQRT.%   Copyright 1984-2008 The MathWorks, Inc.%   $Revision: 1.1.6.2 $  $Date: 2008/03/13 17:32:00 $%   Built-in function.

然后ATAN2D(Y,X)也是

%ATAN2D  Four quadrant inverse tangent, result in degrees.%   ATAN2D(Y,X) is the four quadrant arctangent of the elements%   of X and Y. -180 <= ATAN2D(Y,X) <= 180.%%   See also ATAND, ATAN2.%   Copyright 1984-2011 The MathWorks, Inc.%   $Revision: 1.1.6.1 $  $Date: 2011/12/16 16:32:53 $%   Built-in function.

以上工作都是为了计算梯度，那HOG到底是什么呢，往下看

1 0