如何在图像中绘制猪的特征

Question

I am trying to feature extraction from an image for some certain points. First time I am using HogFeatureextraction. When I plot the features and valid points, I am getting result not on the certain points. I will use these features for training later on. For example, I have points on the straight line. Should not my features on where my certain points on the line. I am a little bit confused about concept of it. I used [features,validPoints] = extractHOGFeatures(I,points). x and y are my 10 positions in the image. In this case how is feature extraction working?

[features,validPoints] = extractHOGFeatures(I,[x,y]); figure; imshow(I); hold on; plot(features, 'ro'); plot(validPoints,'go');

Thank you

Answer 1

The function's documentation explains it all clearly.

validPoints is a nX2 matrix of xy coordinates so you should use plot(x,y) instead of plot(x) to plot it.

features is a matrix of the HoG features of each point, and simply plot it using plot(features, 'ro') will not produce any reasonable output.

However, you can simply obtain the third output ( visualization ) from extractHOGFeatures and then use plot to plot it:

I = im2double(imread('cameraman.tif'));
% desired points
n = 20;
x = randi(size(I,2), [n 1]);
y = randi(size(I,1), [n 1]);
% extract features + visualization object
[features,validPoints,visualization] = extractHOGFeatures(I,[x,y]);
% show image and features
figure;
imshow(I);
hold on;
plot(visualization,'Color','r');
% plot valid points
plot(validPoints(:,1),validPoints(:,2),'go');