WARNING - Complete n00b here.
I'm working on a project which needs to find holes. I found a method that is fairly accurate (bwconncomp) but I get some extra data that I don't need (a.k.a holes that aren't holes). Now the holes are circular so I was just going to do a check with imfindcircles.
So what I need to do is take the center coordinate and radius info from imfindcircles to filter out the non-circular holes in bwconncomp. How should I tackle that?
%Find Circles
[centersDark, radiiDark] = imfindcircles(im,[10 75],'ObjectPolarity','dark');
%Find holes (I think)
cc = bwconncomp(BW);
%Put box around holes (prints to figure for debugging... kinda)
rp = regionprops(cc,'BoundingBox');
So just to clarify, I need to figure out how to weed out the extra info in cc from the data received in from imfindcircles (those variables being centersDark and radiiDark)
Here's a sample image:
You can also improve your segmentation stage:
close all;
% read input
im = imread('holes.bmp');
grayImg = rgb2gray(im);
% create an image where holes are removed
med = medfilt2(grayImg,[100,100],'symmetric');
figure();
imshow(med);
title('median');
% subtract image with holes from image without holes
% so the whole process is less dependent on ilumination of foreground
diff = double(med) - double(BW);
figure();
imshow(uint8(diff+127));
title('difference');
% apply threshold
bw = diff > 50;
figure();
imshow(bw);
title('threshold');
% remove small objects
SE = strel('disk',10);
opened = imopen(bw,SE);
figure();
imshow(opened);
title('imopen');
% get bounding boxes for each hole
cc = bwconncomp(opened);
rp = regionprops(cc,'BoundingBox');
% draw rectangles
figure();
imshow(im);
hold on;
title('result');
for i = 1:length(rp)
rectangle('Position',rp(i).BoundingBox,'EdgeColor','red')
end
Result:
Related
I want to convert an image from Cartesian to Polar and to use it for opengl texture.
So I used matlab referring to the two articles below.
Link 1
Link 2
My code is exactly same with Link 2's anwser
% load image
img = imread('my_image.png');
% convert pixel coordinates from cartesian to polar
[h,w,~] = size(img);
[X,Y] = meshgrid((1:w)-floor(w/2), (1:h)-floor(h/2));
[theta,rho] = cart2pol(X, Y);
Z = zeros(size(theta));
% show pixel locations (subsample to get less dense points)
XX = X(1:8:end,1:4:end);
YY = Y(1:8:end,1:4:end);
tt = theta(1:8:end,1:4:end);
rr = rho(1:8:end,1:4:end);
subplot(121), scatter(XX(:),YY(:),3,'filled'), axis ij image
subplot(122), scatter(tt(:),rr(:),3,'filled'), axis ij square tight
% show images
figure
subplot(121), imshow(img), axis on
subplot(122), warp(theta, rho, Z, img), view(2), axis square
The result was exactly what I wanted, and I was very satisfied except for one thing. It's the area (red circled area) in the picture just below. Considering that the opposite side (blue circled area) is not, I think this part should also be filled. Because of this part is empty, so there is a problem when using it as a texture.
And I wonder how I can fill this part. Thank you.
(little difference from Link 2's answer code like degree<->radian and axis values. but i think it is not important.)
Those issues you show in your question happen because your algorithm is wrong.
What you did (push):
throw a grid on the source image
transform those points
try to plot these colored points and let MATLAB do some magic to make it look like a dense picture
Do it the other way around (pull):
throw a grid on the output
transform that backwards
sample the input at those points
The distinction is called "push" (into output) vs "pull" (from input). Only Pull gives proper results.
Very little MATLAB code is necessary. You just need pol2cart and interp2, and a meshgrid.
With interp2 you get to choose the interpolation (linear, cubic, ...). Nearest-neighbor interpolation leaves visible artefacts.
im = im2single(imread("PQFax.jpg"));
% center of polar map, manually picked
cx = 10 + 409/2;
cy = 7 + 413/2;
% output parameters
radius = 212;
dRho = 1;
dTheta = 2*pi / (2*pi * radius);
Thetas = pi/2 - (0:dTheta:2*pi);
Rhos = (0:dRho:radius);
% polar mesh
[Theta, Rho] = meshgrid(Thetas, Rhos);
% transform...
[Xq,Yq] = pol2cart(Theta, Rho);
% translate to sit on the circle's center
Xq = Xq + cx;
Yq = Yq + cy;
% sample image at those points
Ro = interp2(im(:,:,1), Xq,Yq, "cubic");
Go = interp2(im(:,:,2), Xq,Yq, "cubic");
Bo = interp2(im(:,:,3), Xq,Yq, "cubic");
Vo = cat(3, Ro, Go, Bo);
Vo = imrotate(Vo, 180);
imshow(Vo)
The other way around (get a "torus" from a "ribbon") is quite similar. Throw a meshgrid on the torus space, subtract center, transform from cartesian to polar, and use those to sample from the "ribbon" image into the "torus" image.
I'm more familiar with OpenCV than with MATLAB. Perhaps MATLAB has something like OpenCV's warpPolar(), or a generic remap(). In any case, the operation is trivial to do entirely "by hand" but there are enough supporting functions to take the heavy lifting off your hands (interp2, pol2cart, meshgrid).
1.- The white arcs tell that the used translation pol-cart introduces significant errors.
2.- Reversing the following script solves your question.
It's a script that goes from cart-pol without introducing errors or ignoring input data, which is what happens when such wide white arcs show up upon translation apparently correct.
clear all;clc;close all
clc,cla;
format long;
A=imread('shaffen dass.jpg');
[sz1 sz2 sz3]=size(A);
szx=sz2;szy=sz1;
A1=A(:,:,1);A2=A(:,:,2);A3=A(:,:,3); % working with binary maps or grey scale images this wouldn't be necessary
figure(1);imshow(A);
hold all;
Cx=floor(szx/2);Cy=floor(szy/2);
plot(Cx,Cy,'co'); % because observe image centre not centered
Rmin=80;Rmax=400; % radius search range for imfindcircles
[centers, radii]=imfindcircles(A,[Rmin Rmax],... % outer circle
'ObjectPolarity','dark','Sensitivity',0.9);
h=viscircles(centers,radii);
hold all; % inner circle
[centers2, radii2]=imfindcircles(A,[Rmin Rmax],...
'ObjectPolarity','bright');
h=viscircles(centers2,radii2);
% L=floor(.5*(radii+radii2)); % this is NOT the length X that should have the resulting XY morphed graph
L=floor(2*pi*radii); % expected length of the morphed graph
cx=floor(.5*(centers(1)+centers2(1))); % coordinates of averaged circle centres
cy=floor(.5*(centers(2)+centers2(2)));
plot(cx,cy,'r*'); % check avg centre circle is not aligned to figure centre
plot([cx 1],[cy 1],'r-.');
t=[45:360/L:404+1-360/L]; % if step=1 then we only get 360 points but need an amount of L points
% if angle step 1/L over minute waiting for for loop to finish
R=radii+5;x=R*sind(t)+cx;y=R*cosd(t)+cy; % build outer perimeter
hL1=plot(x,y,'m'); % axis equal;grid on;
% hold all;
% plot(hL1.XData,hL1.YData,'ro');
x_ref=hL1.XData;y_ref=hL1.YData;
% Sx=zeros(ceil(R),1);Sy=zeros(ceil(R),1);
Sx={};Sy={};
for k=1:1:numel(hL1.XData)
Lx=floor(linspace(x_ref(k),cx,ceil(R)));
Ly=floor(linspace(y_ref(k),cy,ceil(R)));
% plot(Lx,Ly,'go'); % check
% plot([cx x(k)],[cy y(k)],'r');
% L1=unique([Lx;Ly]','rows');
Sx=[Sx Lx'];Sy=[Sy Ly'];
end
sx=cell2mat(Sx);sy=cell2mat(Sy);
[s1 s2]=size(sx);
B1=uint8(zeros(s1,s2));
B2=uint8(zeros(s1,s2));
B3=uint8(zeros(s1,s2));
for n=1:1:s2
for k=1:1:s1
B1(k,n)=A1(sx(k,n),sy(k,n));
B2(k,n)=A2(sx(k,n),sy(k,n));
B3(k,n)=A3(sx(k,n),sy(k,n));
end
end
C=uint8(zeros(s1,s2,3));
C(:,:,1)=B1;
C(:,:,2)=B2;
C(:,:,3)=B3;
figure(2);imshow(C);
the resulting
3.- let me know if you'd like some assistance writing pol-cart from this script.
Regards
John BG
Here is the input image 5.png:
Here is my code:
clear all; close all; clc;
%Input Image
A = imread('C:\Users\efu\Desktop\5.png');
% figure, imshow(A);
C=medfilt2(A,[3 5]);
% figure,imshow(C);
D=imfill(C);
% figure,imshow(D);
%Image obtained using MATLAB function 'edge'
E=edge(D,'canny',[0.01 .02],3);
figure, imshow(E); title('Image obtained using MATLAB function');
image=E;
img=im2bw(image);
% imshow(img)
se = strel('line',3,0);
zz = imerode(img,se);
figure, imshow(zz);
Output after canny edge detection:
After Eroding:
Here the problem is that after eroding all horizontal edges are broken, but I don't want that. I want to extract all horizontal lines without breaking, besides want to remove all vertical and diagonal lines.
Please someone modify the code.
It's a hack but it works. A short note, I would advise against using clear all. It has some negative effects such as clearing references to your mex functions. I'm not really sure what that means but there seems to be no real use for it unless you want to clear global variables.
Basically what I did here was threefold. I added a gaussian filter to give a bit more tolerance, increased the erosion rate of strel, and searched across angles to give a bit of angle tolerance. In the end, you have a bit more than you started with on the horizontal part but it does clear the image up a lot better. If you wanted you could just add up the zz matrices and threshold it to get a new binary image which could be a bit closer to your original. Really enjoyed the question by the way and made me look forward to image processing in the fall.
clear; close all;
%Input Image
A = imread('5.png');
% figure, imshow(A);
C=medfilt2(A,[3 5]);
% figure,imshow(C);
D=imfill(C);
% figure,imshow(D);
%Image obtained using MATLAB function 'edge'
E=edge(D,'canny',[0.01 .02],4);
figure, imshow(E); title('Image obtained using MATLAB function');
image=E;
img=double(image);
img = imgaussfilt(img,.5);
% imshow(img)
zz_out = zeros(size(img));
% se = strel('line',3,-90);
% zz = imerode(img,se);
% se2 = strel('line',3,0);
% zz2 = imerode(img,se2);
for ii = -5:.1:5
se = strel('line',20,ii);
zz = imerode(img,se);
zz_out = or(zz,zz_out);
end
% zz_out = img-zz;
figure, imshow(zz_out);
How to count circle objects in a bright image using MATLAB?
The input image is:
imfindcircles function can't find any circle in this image.
Based on well known image processing techniques, you can write your own processing tool:
img = imread('Mlj6r.jpg'); % read the image
imgGray = rgb2gray(img); % convert to grayscale
sigma = 1;
imgGray = imgaussfilt(imgGray, sigma); % filter the image (we will take derivatives, which are sensitive to noise)
imshow(imgGray) % show the image
[gx, gy] = gradient(double(imgGray)); % take the first derivative
[gxx, gxy] = gradient(gx); % take the second derivatives
[gxy, gyy] = gradient(gy); % take the second derivatives
k = 0.04; %0.04-0.15 (see wikipedia)
blob = (gxx.*gyy - gxy.*gxy - k*(gxx + gyy).^2); % Harris corner detector (high second derivatives in two perpendicular directions)
blob = blob .* (gxx < 0 & gyy < 0); % select the top of the corner (i.e. positive second derivative)
figure
imshow(blob) % show the blobs
blobThresshold = 1;
circles = imregionalmax(blob) & blob > blobThresshold; % find local maxima and apply a thresshold
figure
imshow(imgGray) % show the original image
hold on
[X, Y] = find(circles); % find the position of the circles
plot(Y, X, 'w.'); % plot the circle positions on top of the original figure
nCircles = length(X)
This code counts 2710 circles, which is probably a slight (but not so bad) overestimation.
The following figure shows the original image with the circle positions indicated as white dots. Some wrong detections are made at the border of the object. You can try to make some adjustments to the constants sigma, k and blobThresshold to obtain better results. In particular, higher k may be beneficial. See wikipedia, for more information about the Harris corner detector.
How to remove skin parts on segmentation ?
First, I made this first picture smaller, since the picture is somehow intimidating, I'll give the image at the end section.
I'm using RGB & ycbcr segmentation, but it seems the segmentation didn't work well.
clear all;
close all;
clc;
img=imread('acne.jpg');
%ycbcr segmentation
img_ycbcr=img; %image from the previous segmentation
ycbcr=rgb2ycbcr(img_ycbcr);
cb=ycbcr(:,:,2);
cr=ycbcr(:,:,3);
%Detect Skin
%[r,c,v] = find(cb>=77 & cb<=127 & cr>=133 & cr<=173);
[r c v] = find(cb<=77 | cb >=127 | cr<=133 | cr>=173);
numid = size(r,1);
%Mark Skin Pixels
for i=1:numid
img_ycbcr(r(i),c(i),:) = 0;
% bin(r(i),c(i)) = 1;
end
figure
title('ycbcr segmentation');
imshow(img_ycbcr);
%==============================================================
%rgb segmentation
img_rgb=img_ycbcr;
r=img_rgb(:,:,1);
g=img_rgb(:,:,2);
b=img_rgb(:,:,3);
[row col v]= find(b>0.79*g-67 & b<0.78*g+42 & b>0.836*g-14 & b<0.836*g+44 ); %non skin pixels
numid=size(row,1);
for i=1:numid
img_rgb(row(i),col(i),:)=0;
end
figure
imshow(img_rgb);
Here my sample :
I agree with Adriaan. Don't do it with just colour, use additional information such as the shape and the edges.
The last two colorplanes seem to have the most contrast, so let's use one of them:
Nipple = imread('N8y6Q.jpg')
Nipple = imadjust(Nipple(:,:,2));
imshow(Nipple)
[centers, radii] = imfindcircles(Nipple, [30,60]);
hold on
imshow(Nipple);
viscircles(centers, radii);
The circular Hough transform is a robust way to find circular objects if you know the approximate radius range and are satisfied with the approx. location and size of the object.
If not you can try other classical methods, e.g. (Canny) edge detection, using the Hough center point as a marker -> region growing, fitting a snake etc. etc.
To be exact I need the four end points of the road in the image below.
I used find[x y]. It does not provide satisfying result in real time.
I'm assuming the images are already annotated. In this case we just find the marked points and extract coordinates (if you need to find the red points dynamically through code, this won't work at all)
The first thing you have to do is find a good feature to use for segmentation. See my SO answer here what-should-i-use-hsv-hsb-or-rgb-and-why for code and details. That produces the following image:
we can see that saturation (and a few others) are good candidate colors spaces. So now you must transfer your image to the new color space and do thresholding to find your points.
Points are obtained using matlab's region properties looking specifically for the centroid. At that point you are done.
Here is complete code and results
im = imread('http://i.stack.imgur.com/eajRb.jpg');
HUE = 1;
SATURATION = 2;
BRIGHTNESS = 3;
%see https://stackoverflow.com/questions/30022377/what-should-i-use-hsv-hsb-or-rgb-and-why/30036455#30036455
ViewColoredSpaces(im)
%convert image to hsv
him = rgb2hsv(im);
%threshold, all rows, all columns,
my_threshold = 0.8; %determined empirically
thresh_sat = him(:,:,SATURATION) > my_threshold;
%remove small blobs using a 3 pixel disk
se = strel('disk',3');
cleaned_sat = imopen(thresh_sat, se);% imopen = imdilate(imerode(im,se),se)
%find the centroids of the remaining blobs
s = regionprops(cleaned_sat, 'centroid');
centroids = cat(1, s.Centroid);
%plot the results
figure();
subplot(2,2,1) ;imshow(thresh_sat) ;title('Thresholded saturation channel')
subplot(2,2,2) ;imshow(cleaned_sat);title('After morpphological opening')
subplot(2,2,3:4);imshow(im) ;title('Annotated img')
hold on
for (curr_centroid = 1:1:size(centroids,1))
%prints coordinate
x = round(centroids(curr_centroid,1));
y = round(centroids(curr_centroid,2));
text(x,y,sprintf('[%d,%d]',x,y),'Color','y');
end
%plots centroids
scatter(centroids(:,1),centroids(:,2),[],'y')
hold off
%prints out centroids
centroids
centroids =
7.4593 143.0000
383.0000 87.9911
435.3106 355.9255
494.6491 91.1491
Some sample code would make it much easier to tailor a specific solution to your problem.
One solution to this general problem is using impoint.
Something like
h = figure();
ax = gca;
% ... drawing your image
points = {};
points = [points; impoint(ax,initialX,initialY)];
% ... generate more points
indx = 1 % or whatever point you care about
[currentX,currentY] = getPosition(points{indx});
should do the trick.
Edit: First argument of impoint is an axis object, not a figure object.