Check if second image is subimage of first image - image

I want to find out if a given image is an exact or similar part of another image in matlab.
For example, detecting a score bar in a cricket video frame. I would like to detect if there is a scorebar displayed in the given image or not.
1. Larger image
2. Another image
3. Check if this is a subimage
I want to check if 3 is a part of 1 or not. Not an exact part. For example, even if a scorebar exists in 1, and they are not the same scorebars, that would do.
What I am trying:
I am trying to divide the larger image into small parts and take the last part of the image and calculate hue histogram difference with the scorebar image. If it falls below a certain threshold, I should classify that as a part of the bigger image. Is this the right approach or should I follow some other better approach. Please suggest me if you have a better one.
Code I wrote:
rgbImage = imread('img7517.jpg'); %bigger image
[r, c, x] = size(rgbImage);
numberOfBins = 256;
r1 = 6*r/7;
im = rgbImage(r1:r,:,1);
subplot(2,2,1);
imshow(im);
hsv = rgb2hsv(im);
h = hsv(:,:,1);
subplot(2,2,2);
hist(h(:), numberOfBins);
[counts, y] = hist(h(:), numberOfBins);
im1 = imread('scorebar.jpg'); %smaller image
subplot(2,2,3);
imshow(im1);
hsv = rgb2hsv(rgbImage);
h = hsv(:,:,1);
subplot(2,2,4);
hist(h(:), numberOfBins);
[count, y] = hist(h(:), numberOfBins);
c = sum(abs(counts(:) - count(:)));
disp(c);
Problem
But this doesn't give me any significance histogram difference between 1,3 and 2,3. Value of c for 1,3 is 72949 and for 2,3 is 72875. How do I do this? Is the problem due to code or approach? Please help me solve this problem.
Edit:
Trying normalized cross-correlation,
im1 = rgb2gray(imread('replay.jpg'));
im2 = rgb2gray(imread('scorebar1.jpg'));
c = normxcorr2(im2, im1);
[ypeak, xpeak] = find(c==max(c(:)));
yoffSet = ypeak-size(im1,1);
xoffSet = xpeak-size(im1,2);
hFig = figure;
hAx = axes;
imshow(im2,'Parent', hAx);
imrect(hAx, [xoffSet, yoffSet, size(im1,2), size(im1,1)]);
following this link. But doesn't gives a similar analysis.

This class of problem (finding a target image within a larger image) is known as template matching. Typically you might use normalised cross-correlation, but there are various different algorithms, depending on your requirements and specific use case.
Unfortunately your home-brew histogram-based algorithm is probably not going to give very good results, as you have already observed, so you'll probably need to try one of the commonly-used methods described in the articles linked to above.

Solution, I got,
im1 = rgb2gray(imread('img1.jpg'));
im2 = rgb2gray(imread('scorebar.jpg'));
[r, c, x] = size(rgbImage);
numberOfBins = 256;
r1 = 6*r/7;
im1 = im1(r1:r,:,1);
[counts, y] = imhist(im1, numberOfBins);
[count, y] = imhist(im2, numberOfBins);
c = sum(abs(counts(:) - count(:)));
disp(c);
This gives significance hue histogram difference(HHD) between histograms. The images who have scorebars have HHD from 2000-5000, those who don't have scorebars have HHD > 10000.

Related

How to apply Thresholding in image processing

This is sample code for K means algorithm.
k = 5;
[Centroid,new_cluster]=kmeans_algorithm(inv_trans_img,k);
for i_loop = 1:k
cluster = zeros(size(inv_trans_img));
pos = find(new_cluster==i_loop);
cluster(pos) = new_cluster(pos);
figure; imshow(cluster,[]);title('K-means');
end
I need to get the final image from this K means algorithm and I need to pass that image for thresholding process.I did it like below.
tumour_image=cluster;
n = 512;
binarized_img = zeros(n,n);
sort_val = sort(tumour_image(:));
mid_val = ceil(length(sort_val)/2);
threshold = tumour_image(mid_val);
binarized_img(find(tumour_image>=threshold)) = 1;
binarized_img(find(tumour_image<threshold)) = 0;
imshow(binarized_img);title('binarized image');
But now the problem is,only a white image is coming as a result.How can i solve this out.
Your threshold should be:
threshold = sort_val(mid_val);
You need to get the median of the sorted values, not the center element of tumour_image.
As #NeilSlater mentions in the comments, the reason that you're getting an all-white image from your existing code is that you are, by chance, selecting a black pixel from the original image, so when you threshold, the entire image is greater than or equal to that pixel in value.
In the case of images in which the majority of the pixels are 0, this will still give you an all-white image as as result. One way around this, and the most analogous to what you're currently doing, is to take the median of the nonzero pixels.
mid_val = ceil((find(sort_val, 1)+length(sort_val))/2);
Alternatively, if you know which clusters you're interested in you can simply keep only those clusters.
binarized_image = tumour_image >= 3; % keep clusters 3 and above

Image differences detection in matlab

I'm trying to find the broken ligaments for these two photos. Because the patten it got I can use the conv2 function find the general broken areas. However, it is really hard for me think how to make it tell the exact broken ligaments. Can you guys give me some idea for how to find which ligaments are broken please?
Because I'm new to this website, I can not post more photos with 2-D convolution results.
Original Picture
Broken Picture
Make a region growing algorithm inside each perfect square.
Once you get that, calculate the area of that section.
Once you find this, calculate the remaining areas. The larger values will be the broken ligaments :)
img = imread('unbroke.jpg');
level = graythresh(rgb2gray(img));
BW = im2bw(rgb2gray(img),level);
BW2= imdilate(imerode(BW, ones(5)), ones(5));
BW3 = bwmorph(BW2,'remove');
figure, imshow(BW2), hold on[![enter image description here][1]][1]
[H,T,R] = hough(BW2);
P = houghpeaks(H,15,'threshold',ceil(0.3*max(H(:))));
x = T(P(:,2)); y = R(P(:,1));
lines = houghlines(BW2,T,R,P,'FillGap',5,'MinLength',7);
max_len = 0;
for k = 1:length(lines)
xy = [lines(k).point1; lines(k).point2];
plot(xy(:,1),xy(:,2),'LineWidth',2,'Color','green');
% Plot beginnings and ends of lines
plot(xy(1,1),xy(1,2),'x','LineWidth',2,'Color','yellow');
plot(xy(2,1),xy(2,2),'x','LineWidth',2,'Color','red');
% Determine the endpoints of the longest line segment
len = norm(lines(k).point1 - lines(k).point2);
if ( len > max_len)
max_len = len;
xy_long = xy;
end
end
lines from unbroken image
lines from broken image
Now, you know what the line segments are do some matching. Or else find pairs of segments that would be connected (same slope + same x/y intercept) within a threshold.
This may be an interesting way to do this too. I saved the second image only as 'image.jpg'.
I = imread('image.jpg');
J = imbinarize(rgb2gray(I)); % Threshold to get a BW image.
BW = bwpropfilt(~J, 'Area', [35001, 1013283]);
imshow(BW)
shows
For selecting the area thresholds easily, I used https://www.mathworks.com/help/images/calculate-region-properties-using-image-region-analyzer.html
If you don't have a recent MATLAB version where imbinarize or bwpropfilt doesn't exist, you can use equivalent thresholding functions, and regionprops to extract all objects within the area range.

Why does downsample appear as a gray image?

In the implementation of downsampling by a factor of 2 to the image, the downsampled image is gray. What should I do in order to add all of the color components to the downsampling implementation so that it will be a color image?
I = imread('lena.gif','gif');
[j k] = size(I)
x_new = j./2;
y_new = k./2;
x_scale = j./x_new;
y_scale = k./y_new;
M = zeros(x_new,y_new);
for count1 = 1:x_new
for count2 = 1:y_new
M(count1,count2) = I(count1.*x_scale,count2.*y_scale);
end
end
figure,imshow(I);
title('Original Image');
M = uint8(M);
figure,imshow(M);
title('Downsample');
GIF images are what are known as indexed images. This means that what you read in with imread are values that are indices to a colour map. Each index generates a unique colour for you, and that's how GIF images are stored. They choose from a predefined set of colours, and each pixel in the GIF image comes from one of the colours in the colour map.
You first need to convert the image into RGB, and you do that with ind2rgb. However, you need to read in the colour map first with the two-output version of imread. You also will want to convert the images to uint8 as good practice with im2uint8:
[X,map] = imread('lena.gif');
I = im2uint8(ind2rgb(X,map));
What you need to do next is what #NKN suggested. You must apply the algorithm to all channels.
As such, simply make an output matrix that has three channels, and apply the algorithm to each plane independently. If I can make a suggestion, when accessing pixels this way after you downsample, make sure you floor or round the image coordinates so you're not inadvertently specifying locations that aren't defined - things like (13.8, 25.5) for example. Image pixel locations are integer, so you need to make sure the coordinates are integer too.
[X,map] = imread('lena.gif');
I = im2uint8(ind2rgb(X,map));
j = size(I,1); %// Change
k = size(I,2);
x_new = j./2;
y_new = k./2;
x_scale = j./x_new;
y_scale = k./y_new;
M = zeros(x_new,y_new,size(I,3)); %// Change
for jj = 1 : size(I,3) %// Change
for count1 = 1:x_new
for count2 = 1:y_new
M(count1,count2,jj) = I(floor(count1.*x_scale),floor(count2.*y_scale),jj); %// Change
end
end
end
figure,imshow(I);
title('Original Image');
M = uint8(M);
figure,imshow(M);
title('Downsample');
To test this, I'm using the mandrill dataset that's part of MATLAB. It is an indexed image with an associated colour map. These are coincidentally stored in X and map respectfully:
load mandrill;
I = im2uint8(ind2rgb(X,map));
Running the modified code, I get these two figures:
When you read the original image it contains 3 layers, R-G-B (as suggested by #rayryeng:
[X,map] = imread('lena.gif');
I = ind2rgb(X,map);
size(I)
ans =
768 1024 3
You should perform the down-sampling process on all the layers:
The code you provided does not down-sample. A simple downsampling example is as follows:
imshow(I(1:2:end,1:2:end,:))

How to remove non-barcode region in an image? - MATLAB

After I did a 'imclearborder', there are still a bit of unwanted object around the barcode. How can I remove those objects to isolate the barcode? I have pasted my code for your reference.
rgb = imread('barcode2.jpg');
% Resize Image
rgb = imresize(rgb,0.33);
figure(),imshow(rgb);
% Convert from RGB to Gray
Igray = double(rgb2gray(rgb));
% Calculate the Gradients
[dIx, dIy] = gradient(Igray);
B = abs(dIx) - abs(dIy);
% Low-Pass Filtering
H = fspecial('gaussian', 20, 10);
C = imfilter(B, H);
C = imclearborder(C);
figure(),imagesc(C);colorbar;
Well, i have already explained it in your previous question How to find the location of red region in an image using MATLAB? , but with a opencv code and output images.
Instead of asking for code, try to implement it yourself.
Below is what to do next.
1) convert image 'C' in your code to binary.
2) Apply some erosion to remove small noises.( this time, barcode region also shrinks)
3) Apply dilation to compensate previous erosion.(most of noise will have removed in previous erosion. So they won't come back)
4) Find contours in the image.
5) Find their area. Most probably, contour which has maximum area will be the barcode, because other things like letters, words etc will be small ( you can understand it in the grayscale image you have provided)
6) Select contour with max. area. Draw a bounding rectangle for it.
Its result is already provided in your previous question. It works very nice. Try to implement it yourself with help of MATLAB documentation. Come here only when you get an error which you don't understand.
%%hi, i am ading my code to yours at the end of your code%%%%
clear all;
rgb = imread('barcode.jpeg');
% Resize Image
rgb = imresize(rgb,0.33);
figure(),imshow(rgb);
% Convert from RGB to Gray
Igray = double(rgb2gray(rgb));
Igrayc = Igray;
% Calculate the Gradients
[dIx, dIy] = gradient(Igray);
B = abs(dIx) - abs(dIy);
% Low-Pass Filtering
H = fspecial('gaussian', 10, 5);
C = imfilter(B, H);
C = imclearborder(C);
imshow(Igray,[]);
figure(),imagesc(C);colorbar;
%%%%%%%%%%%%%%%%%%%%%%%%from here my code starts%%%%%%%%%%%%%%%%
bw = im2bw(C);%%%binarising the image
% imshow(bw);
%%%%if there are letters or any other noise is present around the barcode
%%Note: the size of the noise and letters should be smaller than the
%%barcode size
labelImage = bwlabel(bw,8);
len=0;labe=0;
for i=1:max(max(labelImage))
a = find(labelImage==i);
if(len<length(a))
len=length(a);
labe=i;
end
end
imag = zeros(size(l));
imag(find(labelImage==labe))=255;
% imtool(imag);
%%%if Necessary do errossion
% se2 = strel('line',10,0);
% imag= imerode(imag,se2);
% imag= imerode(imag,se2);
[r c]= find(imag==255);
minr = min(r);
maxc = max(c);
minc = min(c);
maxr = max(r);
imag1 = zeros(size(l));
for i=minr:maxr
for j=minc:maxc
imag1(i,j)=255;
end
end
% figure,imtool(imag1);
varit = find(imag1==0);
Igrayc(varit)=0;
%%%%%result image having only barcode
imshow(Igrayc,[]);
%%%%%original image
figure(),imshow(Igray,[]);
Hope it is useful

Plot images as axis labels in MATLAB

I am plotting a 7x7 pixel 'image' in MATLAB, using the imagesc command:
imagesc(conf_matrix, [0 1]);
This represents a confusion matrix, between seven different objects. I have a thumbnail picture of each of the seven objects that I would like to use as the axes tick labels. Is there an easy way to do this?
I don't know an easy way. The axes properties XtickLabel which determines the labels, can only be strings.
If you want a not-so-easy way, you could do something in the spirit of the following non-complete (in the sense of a non-complete solution) code, creating one label:
h = imagesc(rand(7,7));
axh = gca;
figh = gcf;
xticks = get(gca,'xtick');
yticks = get(gca,'ytick');
set(gca,'XTickLabel','');
set(gca,'YTickLabel','');
pos = get(axh,'position'); % position of current axes in parent figure
pic = imread('coins.png');
x = pos(1);
y = pos(2);
dlta = (pos(3)-pos(1)) / length(xticks); % square size in units of parant figure
% create image label
lblAx = axes('parent',figh,'position',[x+dlta/4,y-dlta/2,dlta/2,dlta/2]);
imagesc(pic,'parent',lblAx)
axis(lblAx,'off')
One problem is that the label will have the same colormap of the original image.
#Itmar Katz gives a solution very close to what I want to do, which I've marked as 'accepted'. In the meantime, I made this dirty solution using subplots, which I've given here for completeness. It only works up to a certain size input matrix though, and only displays well when the figure is square.
conf_mat = randn(5);
A = imread('peppers.png');
tick_images = {A, A, A, A, A};
n = length(conf_mat) + 1;
% plotting axis labels at left and top
for i = 1:(n-1)
subplot(n, n, i + 1);
imshow(tick_images{i});
subplot(n, n, i * n + 1);
imshow(tick_images{i});
end
% generating logical array for where the confusion matrix should be
idx = 1:(n*n);
idx(1:n) = 0;
idx(mod(idx, n)==1) = 0;
% plotting the confusion matrix
subplot(n, n, find(idx~=0));
imshow(conf_mat);
axis image
colormap(gray)

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