Insert and Remove text from image

Hi guys,

I need your help in solving the following problem:

I have an image which i would like to add to it text but after i need to delete that text, how would i do that if i use the method described in the following link for adding text to images : http://www.mathworks.com/help/vision/ref/inserttext.html#btp_i7c-1

Moreover how would i add labels to point using plot on images?

Thanks in advance.

Answer 1

[Image Analyst]

That method burns text into the image. If you want to undo it, you'd have to still have the original image and just use that again.

To put text into the overlay, use text(). You can get the handle of that and call delete to remove it. The underlying image is not changed at all

hText = text(x, y, string);
% Get rid of it now
delete(hText);

[Sanders A.]

What if I have a cell array of text items from generating them procedurally?

[Image Analyst]

To put into the overlay

for k = 1 : length(ca)
    thisString = ca{k};
    x = whatever;
    y = whatever;
    text(x, y, thisString);
end

To burn into the image, there is this example from the help for insertText:

% Create texts that contain fractions.
text_str = cell(3,1);
conf_val = [85.212 98.76 78.342]; 
for ii=1:3
    text_str{ii} = ['Confidence: ' num2str(conf_val(ii),'%0.2f') '%'];
end
% Define the positions and colors of the text boxes.
position = [23 373;35 185;77 107]; 
box_color = {'red','green','yellow'};
% Insert the text with new font size, box color, opacity, and text color.
RGB = insertText(I,position,text_str,'FontSize',18,'BoxColor',...
    box_color,'BoxOpacity',0.4,'TextColor','white');

[Sanders A.]

Sorry for the unclear question

I had produced text markers on my plot using

textList{jj} = text(x,y,labelList(jj));

and was looking for a way to delete all the labels in one go such as with

delete(textList{:})

But that didn't work. So I just looped through all the elements and deleted them one at a time.

Regardless, I appreciate the time you took to provide such a robust answer!

[DGM]

if you're using a cell array to hold the handles, you could do:

% create a figure with some text objects in it
x = linspace(0,1,3);
y = x;
labelList = {'banana' 'orange','apple'};

hold on;
for jj = 1:numel(x)
    textList{jj} = text(x(jj),y(jj),labelList(jj));
end
pause(2) % pause for dramatic effect

cellfun(@delete,textList) % delete them

But you don't really need to use a cell array for the handles. If you just use a handles array, you can just use delete() by itself.

% create a figure with some text objects in it
x = linspace(0,1,3);
y = x;
labelList = {'banana' 'orange','apple'};

hold on;
for jj = 1:numel(x)
    textList(jj) = text(x(jj),y(jj),labelList(jj));
end

pause(2) % pause for dramatic effect

delete(textList)

[Image Analyst]

@Sanders A. see my Answer below on this page. I just added a new Answer.

https://www.mathworks.com/matlabcentral/answers/264796-insert-and-remove-text-from-image#answer_946700

You can also have functions to delete lines, etc. Just search for 'Type's like 'line', 'xline', etc.

Answer 2

[Image Analyst]

To clear all text from an axes, you can use this function I wrote:

%=====================================================================
% Erases all text labels from the specified axes.
function ClearTextFromAxes(handleToAxes)
try
    handlesToChildObjectsInAxes = findobj(handleToAxes, 'Type', 'text');
    if ~isempty(handlesToChildObjectsInAxes)
        delete(handlesToChildObjectsInAxes);
    end
catch ME
    errorMessage = sprintf('Error in program %s, function %s(), at line %d.\n\nError Message:\n%s', ...
        mfilename, ME.stack(1).name, ME.stack(1).line, ME.message);
    uiwait(warndlg(errorMessage));
end
return; % from ClearTextFromAxes