Calculating mean angles of edge detection

Question

Anna Marshall 2020-4-19

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/519159-calculating-mean-angles-of-edge-detection

评论： Anna Marshall 2020-4-30

Hello,

I'm a new user of Matlab and am looking to calculate the mean and median angles of an image after performing an edge detection. I am using the following edge detection script adapted from the MathWorks edge detection example code and am looking to take it a step further in order to calculate the mean and median angles of the edge detection for each image I input. I eventually am looking to change the code from a specific image to a moving window. Additionally, I'm curious whether it is possible to calculate the number of horizontal, vertical, and diagonal edges from the edge detection output?

Thank you!

clear
RGB=imread('DJI_0022.jpg'); %inputs image
I=rgb2gray(RGB); %convers to grayscale
figure
imshow(I)
%%
%https://www.mathworks.com/help/images/ref/edge.html
%two different types of edge detection
BW1 = edge(I,'Canny');
BW2 = edge(I,'Prewitt');
figure
imshowpair(BW1,BW2,'montage')
%%
%https://www.mathworks.com/matlabcentral/answers/8591-edge-direction
%vertical
BWv = imopen(BW1,[1 1 1]');
%horizontal:
BWh = imopen(BW1,[1 1 1]);
%top left to lower right
BWd = imopen(BW1,[1 0 0; 0 1 0; 0 0 1]);
%%
%plot results
figure
subplot(3,1,1)
imshow(BWv);
title('vertical')
subplot(3,1,2)
imshow(BWh);
title('horizontal')
subplot(3,1,3)
imshow(BWd);
title('diagonal')

3 个评论
显示 1更早的评论隐藏 1更早的评论

darova 2020-4-20

在 MATLAB Online 中打开

I'm curious whether it is possible to calculate the number of horizontal, vertical, and diagonal edges from the edge detection output?

Yes. THe answer is yes. Use bwlabel

[L,n] = bwlabel(BWh,4); % '4' is connection

Little explanation:

I'd use 4 connected object for horizontal and vertical lines. And 8 connected object for diagonals

See more here: bwlabel

Anna Marshall 2020-4-21

Thanks so much! I tried it out and bwlabel works great. Any ideas on how to calculate mean angles for each direction (horizontal, vertical, and diagonal)?

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

darova 2020-4-21

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/519159-calculating-mean-angles-of-edge-detection#answer_427291

在 MATLAB Online 中打开

Try regionprops with orientation property

Example

BWd1 = 1.0*BWd;
data = regionprops(BWd,'orientation','pixelidxlist');   % get orientation and pixels list of each region
for i = 1:numel(data)
    idx = data(i).PixelIdxList;                         % pixel indices of current region
    ori = data(i).Orientation;                          % orintation of region
    BWd1(idx) = ori;                                    % assign angle value
end
imagesc(BWd1)
colorbar

15 个评论
显示 13更早的评论隐藏 13更早的评论

Anna Marshall 2020-4-30

在 MATLAB Online 中打开

Capture.JPG

Absolutely. Your drawing is what I am trying to achieve. I have code that adds up the number of edges at each specified orientation (horizontal, vertical, left diagonal, right diagonal) and then calculates the mean angle of each orientation. What I would like is to modify my code to instead calculate EACH angle and report those values. Below is the code I have for average orientation from my binary edge detected image:

%vertical
BWv = imopen(BW1,[1 1 1]');
%horizontal:
BWh = imopen(BW1,[1 1 1]);
%top left to lower right
BWdleft = imopen(BW1,[1 0 0; 0 1 0; 0 0 1]);
%top right to lower left
BWdright = imopen(BW1,[0 0 1; 0 1 0; 1 0 0]);
%calculate horizontal # of edges
[H,Hnum] = bwlabel(BWh,4); 
%calculate vertical # of edges
[V,Vnum] = bwlabel(BWv,4); 
%calculate diagonal left # of edges
[DL,DLnum] = bwlabel(BWdleft,8); 
%calculate diagonal right # of edges
[DR,DRnum] = bwlabel(BWdright,8); 
%% Diagonal Left orientation
BWdl1 = 1.0*BWdleft;
% get orientation and pixels list of each region
data = regionprops(BWdleft,'orientation','pixelidxlist');   
for i = 1:numel(data)
    % pixel indices of current region
    idxDL = data(i).PixelIdxList;     
    % orientation of region
    oriDL = data(i).Orientation;   
    % assign angle value
    BWdl1(idxDL) = oriDL;                                    
end
imagesc(BWdl1)
colorbar
%% Vertical Orientation
BWv1 = 1.0*BWv;
data = regionprops(BWv,'orientation','pixelidxlist');   % get orientation and pixels list of each region
for i = 1:numel(data)
    idxV = data(i).PixelIdxList;                         % pixel indices of current region
    oriV = data(i).Orientation;                          % orintation of region
    BWv1(idxV) = oriV;                                    % assign angle value
end
imagesc(BWv1)
colorbar
%% Horizontal Orientation
BWh1 = 1.0*BWh;
data = regionprops(BWh,'orientation','pixelidxlist');   % get orientation and pixels list of each region
for i = 1:numel(data)
    idxH = data(i).PixelIdxList;                         % pixel indices of current region
    oriH = data(i).Orientation;                          % orintation of region
    BWh1(idxH) = oriH;                                    % assign angle value
end
imagesc(BWh1)
colorbar
%% 
%% Diagonal Right orientation
BWdr1 = 1.0*BWdright;
data = regionprops(BWdright,'orientation','pixelidxlist');   % get orientation and pixels list of each region
for i = 1:numel(data)
    idxDR = data(i).PixelIdxList;                         % pixel indices of current region
    oriDR = data(i).Orientation;                          % orintation of region
    BWdr1(idxDR) = oriDR;                                    % assign angle value
end
imagesc(BWdr1)
colorbar

darova 2020-4-30

Try wrapTo360

Anna Marshall 2020-4-30

Thanks! I'll give that a try

请先登录，再进行评论。

Answer 2

Image Analyst 2020-4-21

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/519159-calculating-mean-angles-of-edge-detection#answer_427380

If you have the Computer Vision Toolbox, try extractHOGFeatures() to get the histogram of oriented gradients.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Anna Marshall 2020-4-21

DJI_0022.JPG

The extractHOGFeatures() tool is neat just from working throught the examples. Is there a way to clip the tool to a specific area of the image or train it so that it is only extratcting the HOG features for the area of interest. For example, in the image attached, I am interested in looking at the logs but not the vegetation and trees. Thank you!

请先登录，再进行评论。

Calculating mean angles of edge detection

3 个评论
显示 1更早的评论隐藏 1更早的评论

采纳的回答

15 个评论
显示 13更早的评论隐藏 13更早的评论

更多回答（1 个）

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

另请参阅

类别

标签

产品

Community Treasure Hunt

Calculating mean angles of edge detection

3 个评论 显示 1更早的评论隐藏 1更早的评论

采纳的回答

15 个评论 显示 13更早的评论隐藏 13更早的评论

更多回答（1 个）

1 个评论 显示 -1更早的评论隐藏 -1更早的评论

另请参阅

类别

标签

产品

Community Treasure Hunt

3 个评论
显示 1更早的评论隐藏 1更早的评论

15 个评论
显示 13更早的评论隐藏 13更早的评论

1 个评论
显示 -1更早的评论隐藏 -1更早的评论