How to sum pixels of a certain area and put a point to stop

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Stelios Fanourakis
Stelios Fanourakis 2019-1-12
评论： Image Analyst 2019-1-14
Hi
I want to sum all pixels of a certain area of the image and the summation will go on (vertically) until it finds the first red pixel where it should stop and move to the next column. Please help
clc;
s = imread('A2.jpg')
for i = 136:548
for j = 123:length(s)
s(i,j)=sum(s)
if s(i,j)== 100
break
end
s = s+1;
end
end
I use this code but I get the error "Assignment has more non-singleton rhs dimensions than non-singleton subscripts" at line s(i,j)=sum(s) .
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Stelios Fanourakis
Stelios Fanourakis 2019-1-12
It gives me 0 0 0 results. I want to count all pixels for the whole column from those points down until the first red pixel where it should stop counting and move forward to the next column.
Stelios Fanourakis
Stelios Fanourakis 2019-1-12
But I get results when I use
theSums = sum(subImage, 2);
Is there an option to have the number of pixels for every column?
E.g.
Column 1:
0 0 74 74 255 255 65 66
Column 2:
1 1 0 0 74 74 255 255 23
Column 3:
0 0 67 67 67 88 88 112 113
etc...

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采纳的回答

Image Analyst
Image Analyst 2019-1-12
If you want to start at some row, and go down to some other row where the red line is for that column (which varies from column to column), use code like this:
% Column 1:
c1 = [0 0 74 74 255 255 65 66 0]'
% Column 2:
c2 = [1 1 0 0 74 74 255 255 23]'
% Column 3:
c3 = [0 0 67 67 67 88 88 112 113]'
% Make image
grayImage = [c1,c2,c3]
% Let's say the red line is at these 3 rows:
redLines = [7, 8, 6];
% Sum from 2 to the red line
[rows, columns] = size(grayImage)
theSums = zeros(1, columns);
theCounts = zeros(1, columns);
startingRow = 2;
for col = 1 : columns
theSums(col) = sum(grayImage(startingRow : redLines(col), col));
theCounts(col) = redLines(col) - startingRow + 1;
end
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Stelios Fanourakis
Stelios Fanourakis 2019-1-13
编辑：Stelios Fanourakis 2019-1-13
  1. It is a jpg image. The contour was drew by the user, using a vector software with red colour.
  2. As I have explained earlier, I only care for the bottom red line, that is already in the image. So, I have to track the red pixels. The user will draw the red line and then the algorithm will sum the pixels until the line the user drew.
Can you please remind me the code you gave me for? As far, it is working satisfactory but I need to find why it gets so jaggy, where it should match the contour red line which is smooth. So, something goes wrong
Image Analyst
Image Analyst 2019-1-14
I think this does what you want.
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
workspace; % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 16;
%===============================================================================
% Get the name of the image the user wants to use.
baseFileName = 'A2.jpg';
folder = pwd;
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
% The file doesn't exist -- didn't find it there in that folder.
% Check the entire search path (other folders) for the file by stripping off the folder.
fullFileNameOnSearchPath = baseFileName; % No path this time.
if ~exist(fullFileNameOnSearchPath, 'file')
% Still didn't find it. Alert user.
errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
uiwait(warndlg(errorMessage));
return;
end
end
%=======================================================================================
% Read in demo image.
rgbImage = imread(fullFileName);
% Get the dimensions of the image.
[rows, columns, numberOfColorChannels] = size(rgbImage)
% Display image.
subplot(2, 3, 1);
imshow(rgbImage, []);
impixelinfo;
axis on;
caption = sprintf('Original Color Image\n%s', baseFileName);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0.05 1 0.95]);
% Get rid of tool bar and pulldown menus that are along top of figure.
% set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
drawnow;
%===================================================================================
% FIND THE RED MASK
% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
% get a mask for the red line.
mask = redChannel > greenChannel;
% Display the image.
subplot(2, 3, 2);
imshow(mask);
caption = sprintf('Color Segmentation Mask Image');
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
impixelinfo;
axis('on', 'image');
drawnow;
% fill holes.
mask = imfill(mask, 'holes');
% Take the largest blob only.
mask = bwareafilt(mask, 1);
% Shrink two layers of pixels to come inside the red lines.
mask = imerode(mask, true(5));
% Display the image.
subplot(2, 3, 3);
imshow(mask);
title('Final Mask', 'FontSize', fontSize, 'Interpreter', 'None');
impixelinfo;
axis('on', 'image');
% Get a masked image.
% Mask the image using bsxfun() function to multiply the mask by each channel individually.
maskedRgbImage = bsxfun(@times, rgbImage, cast(mask, 'like', rgbImage));
% Display the image.
subplot(2, 3, 4);
imshow(maskedRgbImage);
title('Masked RGB Image', 'FontSize', fontSize, 'Interpreter', 'None');
impixelinfo;
axis('on', 'image');
% A = contour(mask,'b');
set(gca,'ydir','reverse')
conversion = 0.9183; % in mm/pixel
addMM = @(x) sprintf('%.3fmm', x * conversion);
xticklabels(cellfun(addMM, num2cell(xticks'), 'UniformOutput', false));
yticklabels(cellfun(addMM, num2cell(yticks'), 'UniformOutput', false));
%===================================================================================
% FIND THE HEIGHT OF THE MASK, AND SUM OF GRAY LEVELS FROM ROW 1 TO RED ROW.
topRow = 1; % Whatever you want.
grayLevelSum = zeros(1, columns); % Initialize sums for every column.
heights = zeros(1, columns); % Initialize heights for every column.
% Find the left and right column of the mask so we know where to sum over.
[rows, columns] = find(mask);
col1 = min(columns);
col2 = max(columns);
for col = col1 : col2
row2 = find(mask(:, col), 1, 'last'); % Get bottom row of mask
if ~isempty(row2)
% Get the sum in the GREEN channel, from row1 to row2.
grayLevelSum(col) = sum(greenChannel(topRow:row2, col));
% Compute the height of the mask at every column.
heights(col) = sum(mask(topRow:row2, col));
end
end
% Plot integrated gray level.
subplot(2, 3, 5);
plot(grayLevelSum, 'b-', 'LineWidth', 2);
xlabel('Column', 'FontSize', 20);
ylabel('Sum of gray levels in column', 'FontSize', 20);
title('Sum of gray levels in column', 'FontSize', 20);
grid on;
% Plot heights
subplot(2, 3, 6);
plot(heights, 'b-', 'LineWidth', 2);
xlabel('Column', 'FontSize', 20);
ylabel('Height of mask in column', 'FontSize', 20);
title('Mask Height vs. Column', 'FontSize', 20);
grid on;
% Tell user the answer.
message = sprintf('Done!');
uiwait(helpdlg(message));

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