How to make next page in GUI

Hello

I am making image browser and I have problem with button Next Page everytime when I press button next page I want to show next 12 images and I am using this code:

for j = (jj+1) : (2*jj)
    [I cmap] = imread(img(j),'frames','all');
    ax=subplot(4,3,(j-12));
    image(I);
    colormap(ax,cmap);
    axis off;
    axis image;
end

where jj=12 first is showen 12 images and pressing Next Page button there should be displayed next 12. This code works when I press button Next Page first time after I run GUI but it doesn't work when I hit it second or third time...What should I do to display 12 new images every time I hit button Next Page

Thank you!

Answer 1

[Image Analyst]

What is img(j)? How is that a color or black and white image? It should be a filename string.

[Image Analyst]

And I'm not seeing the 'frames' option for imread() listed in the documentation.

[Lolipop]

function NextPage_Callback(hObject, eventdata, handles)
% hObject    handle to NextPage (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
    global img
    global jj
    global path
      for j=(jj+1):(2*jj)
[I cmap] = imread(strcat(path,img(j).name),'frames','all');
ax=subplot(4,3,(j-12));
image(I);
colormap(ax,cmap);
axis off;
axis image;
end

Where img.name(j) are the names of images that should be displayed This code is working only for the first next page so when I press button Next Page it really displays next 12 images but the problem is when I try to press it again to display second next page there it doesn't work

[Image Analyst]

I think it's working, it's just displaying the same 12 images as the first time though. Try adding

jj = jj + 12;

after the end of the loop so that it will take the next 12 images the next time it comes in to this callback.

Instead of

ax=subplot(4,3,(j-12));

you might need this

ax=subplot(4,3, mod(j,12)+1);

[Lolipop]

Woow..it's working thank you sooo much

[Lolipop]

How is that a color or black and white image? I don't get this... should I use colormap or what?

[Image Analyst]

Not sure what you're asking. If it's a color image you can't use a colormap - it does not apply. If it's an indexed image then the colormap is probably stored along with the image and you can ask imread() for it and apply it. If it's a grayscale image, you can use the gray(256) colormap (the default if you display it with imshow() but not for image() or imagesc()), or you can apply some other one if you want, such as jet(256) or parula(256) or whatever.

Answer 2

[Sean de Wolski]

I probably doesn't remember what j is.

Put a breakpoint on the line that isn't working, run it, and see what the variables are as you press the button.

[Lolipop]

This is working when I press Next Page first time but when I press second time it doesn't work... I thought that every time when I press push button that for loop would execute

[Sean de Wolski]

So put a break point on the imread line. Press next page, step through, is what you expect to happen, happening? If not, why not? If so, press it again and repeat until you see a discrepancy between expectations and reality.

web(fullfile(docroot, 'matlab/matlab_prog/debugging-process-and-features.html'))

Working your way through this might be worth your time.

[Lolipop]

Thank you Sean de Wolski for helping me and this debugger could be really useful :)

Answer 3

[Sean de Wolski]

probably

(j-12);

Which will not always be 1:12. Instead:

count = 0;
for j = jj:etc
 count = count+1;
 subplot(3,4,count)
 etc.
end

NOTE with the debugger you would be able to walk through and see what each thing is on each step to avoid guessing.