MATLAB Answers

Burn Grid onto a Series of Images

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Hi all-I have a lot of image files and onto each I am trying to place a grid. I'd like to save the grid onto the file, and so produce a new image with the grid in a separate folder. In the end I will have one folder with the original files and a second with the files+grid.
Just now I have this:
for i = 1:fileCount2
image = imread(png);
axis on;
[rows, columns, numberOfColorChannels] = size(image);
hold on;
stepSize = 20; % Whatever you want.
for row = 1 : stepSize : rows
line([1, columns], [row, row], 'Color', 'r', 'LineWidth', 1);
for col = 1 : stepSize : columns
line([col, col], [1, rows], 'Color', 'r', 'LineWidth', 1);
% for x=1:length(fileCount2)
% outputBaseFileName = sprintf('-%4.4d.png', x); %output filename, each frame numbered from 0001
outputFullFileName = fullfile(strcat(outputFolder, '\FramesGrids'), strcat(baseFileName, outputBaseFileName)); %full output filename with .avi file number
imwrite(image, outputFullFileName, 'png'); %write output png file
This successfully adds a grid onto the first photo in the folder, and saves a new photo in a separate folder, but the grid is not saved. The grid only shows up when I run the code and produce the figure within Matlab.
So, any advice on how to save the grid? And how to fix my loop so that every photo has a grid added, not just the first?
Thanks in advance!!
Louise Wilson
Louise Wilson on 12 Jul 2019
Thanks! This doesn't give me lines though, it gives me a dotted grid? Kind of looks like the skeleton of a grid. How do I join the dots?
I don't mean linewidth, I mean the distance between the lines, and where exactly the lines go? How do I specify this accurately so the spacing is consistent.

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Accepted Answer

Image Analyst
Image Analyst on 12 Jul 2019
Simply burn it into the image itself:
grayImage = imread('cameraman.tif');
[rows, columns, numberOfColorchannels] = size(grayImage);
% Make grid every 64 rows
for row = 8 : 64 : rows
grayImage(row, :, :) = 255;
% Make grid every 32 columns
for col = 8 : 32 : rows
grayImage(:, col, :) = 255;
0000 Screenshot.png
Image Analyst
Image Analyst on 13 Jul 2019
No, swapping positions wouldn't do it because then the badly-named image would not have been defined yet by the time you call fileparts().
[folder, baseFileName, extentions] = fileparts(image); % Will throw error because image is not defined yet.
image = imread('02052019-0006.png');
But whatever, glad you got it working and thanks for accepting.

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