How to load an image to a figure using uigetfile/imread?

Hello,

Novice coder here with a question that I am certain there will be an easy answer to - it just escapes me at the moment...

I am simply trying to display an image that I select from my PC's location, in a figure for further analysis. I actually have the analysis code working, but the problem I am having is that when I use uigetfile to provide the 'file look-up', I can navigate to the file, get the figure to launch, but the image then doesn't write to the figure. My code thus far is:

[filename, pathname] = uigetfile(...    
    {'*.jpg; *.JPG; *.jpeg; *.JPEG; *.img; *.IMG; *.tif; *.TIF; *.tiff, *.TIFF','Supported Files (*.jpg,*.img,*.tiff,)'; ...
    '*.jpg','jpg Files (*.jpg)';...
    '*.JPG','JPG Files (*.JPG)';...
    '*.jpeg','jpeg Files (*.jpeg)';...
    '*.JPEG','JPEG Files (*.JPEG)';...
    '*.img','img Files (*.img)';...
    '*.IMG','IMG Files (*.IMG)';...
    '*.tif','tif Files (*.tif)';...
    '*.TIF','TIF Files (*.TIF)';...
    '*.tiff','tiff Files (*.tiff)';...
    '*.TIFF','TIFF Files (*.TIFF)'},...    
    'MultiSelect', 'on');

% Error check - if no filename there is an error
if isequal(filename,0)
    error(' Load Error: No files selected! Load cancelled.')
else

end

% launch the figure box
figure

imagefilename = imgfile(filename,pathname);
c = imread(imagefilename);
image(c)
axis image
grid on

I'm certain the problem is the bit after I launch the figure, but I have tried several different combinations of syntax, but just cant get it right.

Could anyone offer some wizardry to put me right please?

Best regards,

10B.

Answer 1

[Image Analyst]

I think you want fullfile() instead of imgfile().

% Have user browse for a file, from a specified "starting folder."
% For convenience in browsing, set a starting folder from which to browse.
startingFolder = 'C:\Program Files\MATLAB';
if ~exist(startingFolder, 'dir')
  % If that folder doesn't exist, just start in the current folder.
  startingFolder = pwd;
end
% Get the name of the file that the user wants to use.
defaultFileName = fullfile(startingFolder, '*.*');
[baseFileName, folder] = uigetfile(defaultFileName, 'Select a file');
if baseFileName == 0
  % User clicked the Cancel button.
  return;
end
fullFileName = fullfile(folder, baseFileName)
myImage = imread(fullFileName);
imshow(myImage);

[10B]

Hello Image Analyser,

With a name like that - you must be the right person for this query!

Your code works correctly, thanks, but there is a small problem. In my code, I used this to get the image plotted with pixel numbers and a grid over the figure:

axis image
grid on

but when I add that to your code, even corrected to myImage thus:

axis myImage
grid on

it doesn't do what it did previously i.e. grid/numbers. Is this because the command imshow has been used? Is there another fix for this?

Regards,

10B.

[Image Analyst]

myImage is not one of the arguments to axis - it probably ignored it. I don't know why you changed it. What do you want to do? Do you want to show axes and tick marks and labels? If so do

axis on;

Do you want to mouse around and show the location and gray level in a status panel? If so, use impixelinfo().

[10B]

Ha - so simple! Thanks again. What I want to do is have the gridlines over the top of the image, so I can visually create the extents for a bounding box (tried to code a bounding box but couldn't get that to work either!). For example, I can look at the grid take the X,Y extents and then use that to clip the image down to my area of interest. So is there a way to put the gridlines over the top?

[10B]

Ive sorted for myself now! just using grid on works just fine, and I wrote the following to improve the grid colours over the image:

axis on;
grid on; 
set(gca, 'xcolor', 'w', 'ycolor', 'w');

Anyway, thanks for your help and earlier code.

[Image Analyst]

"grid on" sort of makes grid lines over the image but they're dotted and hard to see. If you want nice, high-contrast, solid color lines over the image, you should use line():

% Make horizontal lines every 50 rows.
hold on;
for row = 1 : 50 : rows
    line([1, columns], [row, row], 'Color', 'r');
end
% Make vertical lines every 75 columns.
for col = 1 : 75 : columns
    line([col, col], [1, rows], 'Color', 'r');
end

[10B]

Yes, thats a good suggestion - the dotted lines aren't great TBH, which is why I put them in white. I have tried to use your last bit of code, but I'm running into errors.

I leave axis on and remove grid on like this:

fullFileName = fullfile(folder, baseFileName);
myImage = imread(fullFileName);
imshow(myImage);
axis on;
hold on;
for row = 1 : 50 : rows
    line([1, columns], [row, row], 'Color', 'r');
end
% Make vertical lines every 75 columns.
for col = 1 : 75 : columns
    line([col, col], [1, rows], 'Color', 'r');
end

but unfortunately, it doesn't add the solid lines over the image. I have also tried different combinations of with the grid, without the axis etc. and all no joy as it throws the following error:

"Undefined function or variable 'rows'.

Error in Untitled7 (line 27) for row = 1 : 50 : rows"

I also tried to put the rows in single quote and enclose that section in parenthesis like this:

    hold on;
    for row = (1 : 50 : 'rows')
        line([1, columns], [row, row], 'Color', 'r');

but that simply threw another error:

"For colon operator with char operands, first and last operands must be char.

Undefined function or variable 'rows'."

The Doc Help on rows/columns doesn't really address what this problem may be - other then to say rows/columns are unassigned variables. Sorry to ask again, but do you have another insight on this problem?

Answer 2

[Rafael Lozano]

This was very usefull for me, thaks to all!