Try this:
% Find both sides of a peak.
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
clear; % Erase all existing variables. Or clearvars if you want.
workspace; % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 15;
%==================================================================================
% % Mahsa forgot to upload data so I'm forced
% to try to recreate it from the image.
rgbImage = imread('image.png');
imshow(rgbImage)
axis on
grayImage = rgb2gray(rgbImage);
imshow(grayImage);
impixelinfo
mask = grayImage == 255;
props = regionprops(mask, 'BoundingBox');
% Shrink by 8 to get away from tick marks.
bb = props.BoundingBox
bb(1) = bb(1) + 8;
bb(2) = bb(2) + 8;
bb(3) = bb(3) - 16;
bb(4) = bb(4) - 16;
grayImage = imcrop(grayImage, bb);
imshow(grayImage);
[rows, columns] = size(grayImage);
y = zeros(columns, 1);
for col = 1 : columns
t = find(grayImage(:, col) < 255, 1, 'first');
if ~isempty(t)
y(col) = rows - t;
end
end
figure
x = linspace(2.54e5, 2.69e5, length(y));
% Scale y to -50 to +275
y = rescale(y, -50, 275);
plot(x, y, 'b-', 'LineWidth', 2);
grid on;
%==================================================================================
% Now we have our data and can begin.
[peakValues, indexesOfPeaks] = findpeaks(y, 'MinPeakHeight', 15);
numPeaks = length(peakValues);
peakLeft = ones(1, numPeaks);
peakRight = ones(1, numPeaks);
% Find valley to the left of the peak
hold on;
for k = 1 : numPeaks
plot(x(indexesOfPeaks(k)), y(indexesOfPeaks(k)), 'r+', 'LineWidth', 2, 'MarkerSize', 20);
for k2 = indexesOfPeaks(k) : -1 : 1
if y(k2) > y(k2+1)
break;
end
end
peakLeft(k) = k2;
end
% Find valley to the right of the peak
for k = 1 : numPeaks
for k2 = indexesOfPeaks(k) : length(y)-1
if y(k2+1) > y(k2)
break;
end
end
peakRight(k) = k2;
end
% If you want locations in terms of x instead of indexes:
xLeft = x(peakLeft);
xRight = x(peakRight);
% Plot red lines on the left and red lines on the right.
for k = 1 : length(xLeft)
xline(xLeft(k), 'Color', 'g', 'LineWidth', 3);
xline(xRight(k), 'Color', 'r', 'LineWidth', 3);
end
