MATLAB: [HELP] Finding the lowest positioned pixel in the figure.

binaryheightimagelowestpixelpointsearch

I have a code as follow: which is converted into binary image.

image= [pos1];
BW = im2bw(pos1,map,0.4);
imshow(pos1(:,:)),figure, imshow(BW)
image= [pos2];
BW = im2bw(pos2,map,0.4);
imshow(pos2(:,:)),figure, imshow(BW)

which will return following images

with these images, I want to find the lowest point (as circled with red) and print the location information into one matrix. (only need y axis value) = Height from the bottom of the image. (the first white pixel)

for instance if in lowest point pixel in image1 located at 123,342, and for image 2 located at 134,423

then I want to have matrix that has values of 343, and 423.

I was doing this manually for 10 images. and I gave up as there are 100s of them…

It would be really appreciate if you can help me with this.

Best Answer

Guillaume's answer is good. I just wanted to add: don't do this:

image= [pos1];

All that does it to destroy the built-in function called image(), and nothing useful whatsoever in your code. It can be eliminated without any problem. Never use "image" as the name of a variable.

By the way, another possible method to find the lowest row is

lowestRow1 = find(sum(BW1, 2)>0, 1, 'last');  % Bottom dot in image #1
lowestRow2 = find(sum(BW2, 2)>0, 1, 'last');  % Bottom dot in image #2
output = [lowestRow1, lowestRow2];  % The output array you said you wanted.

Basically you're summing the image horizontally (across columns, which gives a mean vertical profile) and finding the last (lowest) row that has something in it. However I'm not sure why you want 343 and 423 when the lowest rows are 342 and 423 - why add 1 to the first image???

Related Solutions

MATLAB: Highlighting the contour of a specific region and its lowest end points.

I have solved the problem. The code is as below:

crownAndSecondaryDroplet=imread('inputImage.png');
%get the row number of the lowest white pixels
lowestRow = find(sum(crownAndSecondaryDroplet, 2)>0, 1, 'last');  % Bottom white row of the image
hp = impixelinfo(); %to check the output of the lowest row
%find the column numbers of the lowest row
colummsOfLowestRow= find(crownAndSecondaryDroplet(lowestRow,:)==1);
%find the x value for the leftmost and the rightmost pixels of the lowest row
lowestLeftXvalue = min(colummsOfLowestRow);
lowestRightXvalue = max(colummsOfLowestRow);
%get the boundary of the contour
boundary = bwtraceboundary(crownAndSecondaryDroplet,[lowestRow, lowestLeftXvalue],'N'); 
%display the image
figure, imshow(crownAndSecondaryDroplet, []);
title('Image with Rim Contour', 'FontSize', fontSize, 'Interpreter', 'None'); 
axis on;
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
hold on;
%plot the contour and lowest end points
plot(boundary(:,2),boundary(:,1),'g','LineWidth',2);
plot(lowestLeftXvalue , lowestRow, 'r+', 'LineWidth', 3, 'MarkerSize', 20 ); 
plot(lowestRightXvalue , lowestRow, 'r+', 'LineWidth', 3, 'MarkerSize', 20 ); 
hold off;

MATLAB: Moving a greyscale image such that the lowest pixel with an intensity above 0 is at the bottom of the image.

Use the circshift function, which shifts arrays along one dimension. Here is an example:

%generate an image (matrix)
A = rand(6,9)
%find linear index of the minimum value
[~,ix] = min(A(:));
%convert linear index into subscript index
[r,c] = ind2sub(size(A),ix)
%shift image rows to put the lowest valued pixel at the bottom
Y = circshift(A,size(A,1)-r,1)
%additionally, you can also shift image columns to put the lowest valued pixel at the left
Y = circshift(Y,size(A,2)-c+1,2)

Check it out.

Best Answer

Related Solutions

MATLAB: Highlighting the contour of a specific region and its lowest end points.

MATLAB: Moving a greyscale image such that the lowest pixel with an intensity above 0 is at the bottom of the image.

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