I currently use Matlab's imshow to output an image at every iteration of a diffusion filter process, i.e. multiple times per second.
Sometimes during filtering I want a closer look at specific image parts.
However, when using the ('Parent', handle) name-value pair for imshow the magnification and position gets reset.
Is there a way to update the underlying image but having the magnification and position intact?
You can update the cdata in the current axis to your new data matrix which will keep all other settings the same. If this is in a loop, you probably need to call drawnow. E.g:
x=randn(100);
figure;imagesc(x);
Now zoom / pan / do whatever manipulations you want.
f=gca;
x=randn(100);
f.Children.CData = x;
This method of updating of child data is recommended by Matlab as more efficient than destroying the axis child Image and recreating each frame (can't remember the source, it was in one of the help files).
Edit: Just remembered that this syntax won't work on older versions of matlab (pre 2015 or so). In that case, use get/set syntax:
set(get(gca,'Children'),'CData',x);
Related
I am trying to get better quality phase plots of complex functions made with the Complex Function Explorer of E. Wegert CFE. For this purpose I apply the Matlab anti-aliasing function myaa.m to the phase plots that are made with the CFEGUI.m. For the example screenshot of the result window below I used the setting myaa([8 8]) in the Matlab command window which means that the supersampling enlarge the figure 8x and then downscale it to 1/8 to get the original h x w.
As one can see the window of the figure has no operation icons or menu options for save or print. My question is what to do with such a figure (beside making screenshots)? Can I somehow use export-fig to save such a figure or load it in an image array and if yes, how?
It is also possible to use the setting myaa([8 1]) which results in a very large figure window that is larger than my screen (and has the unpleasant attribute that it can not be moved). It would be even better if such a whole figure could be saved (not only the visible part).
You can use getframe to grab current figure information in pixels.
However, while I do not know how this affects you, notice that MATLAB versions above 2014b (included) have already anti-aliasing. The code you linked seem to be from 2008, I am not 100% sure if it has become obsolete now.
I have a line which is plotted on another scatter plot. This line changes its shape from time to time. Is there any way by which I can specify in my program that the data for drawing this line is dynamic so that the plot updates by itself when the data changes?
Now what I am doing is draw the entire figure again after each data update. The program has very large number of iterations(>5000) and I need to visualize every change. That means figure should be drawn 5000 times. This is making my program very slow. Is there any other better way of doing this?
The refreshdata function might do what you want.
To automatically update a graph when a source variable changes, use the linkdata function. MathWorks has a is a great introduction page. However, there is a short example in the documentation:
x = [1:20];
y = rand(20,3);
area(x,y)
linkdata on
Then you can change a variable and the plot automatically redraws:
y(10,:) = 0;
Automatic update.
Note: Changing the source to a different variable entirely is a different thing. If YDataSource is reassigned, then refreshdata would be needed, as pointed out by Molly. Otherwise, this will keep your plot up-to-date when the variable changes.
One caveat is described on this page:
linkdata buffers updates to data and dispatches them to plots at roughly half-second intervals. This makes data linking not suitable for smoothly animating changes in data values unless they are updated in loops that are forced to execute two times per second or less.
I have drown several graphs thanks to "subplot" function on MatLab and it works well.
Nevertheless, I want all my graphs to have the same Y-scale so that I can compare them.
I used the "linkaxes" function and my all my graphs have the same scale but the problem is that some of my figures are "beheaded", lacking their upper part, or one of my figures is completely squeezed.
I don't get what happened. Could you please help me to solve the problem or tell me about another function that would be more appropriate in my case?
Here's part of my code:
for i=1:1:9
m=n(i);
fichier=sprintf('%d.txt',m);
M=load(fichier);
z=length(M(:,1));
x=M(1:z,1);
y=M(1:z,2);
a(i)=subplot(2,4,i)
contour3=plot(x,y)
linkaxes(a,'y')
end
linkaxes creates a permanent link between the scales of several axes, so that you can subsequently perform zoom operations (perhaps interactively) on one, and have the other automatically update.
If you need that functionality, then linkaxes is the right command (although you could possibly also look at linkprops).
However if all you need is to ensure that the y-axis limits of your axes are the same, it will probably be easier (and you will have more control) if you set them directly. You can retrieve the y-axis limits using ylim(axis_handle) and set them using ylim(axis_handle, [lower, upper]), or alternatively with get(axis_handle,'YLim') and set(axis_handle,'YLim',[lower,upper]). You might also look at the YLimMode property of the axis, which determines whether the axis limits are directly set or automatically resized.
I plotted few points using scatter and then label them using text. The position of these labels are same as the position of the points + some offset. Some of these text label overlap with each other and hence I moved them interactively (using mouse). I can check the new position of each of these text individually using property editor. However this is very time-consuming. Is there a better way to get the coordinates of all these text-label?
You can use findobj to get handles to text objects that are children of the current axes (or another handle... your choice):
text_handles = findobj('parent',gca,'type','text');
Then you can get the positions of these text objects:
positions = get(text_handles,'position');
You may need to do a bit more work to associate each text object with its data point - I suggest taking advantage of the property system, perhaps via the UserData field, for this, though there are many options.
If you want to do it easily later do this in your plots, for example:
h=text(2.9,7.5,'MyText');
This will put "MyText" at position 2.9, and 7.5.
Then to change the position use:
set(h,'Position',[2.5 7]);
This will change the position to 2.5 and 7.
Later if you need to see tthe position of text again use:
get(h);
Hope this helps.
I have a question about the values returned by getPosition. Below is my code. It lets the user set 10 points on a given image:
figure ,imshow(im);
colorArray=['y','m','c','r','g','b','w','k','y','m','c'];
pointArray = cell(1,10);
% Construct boundary constraint function
fcn = makeConstrainToRectFcn('impoint',get(gca,'XLim'),get(gca,'YLim'));
for i = 1:10
p = impoint(gca);
% Enforce boundary constraint function using setPositionConstraintFcn
setPositionConstraintFcn(p,fcn);
setColor(p,colorArray(1,i));
pointArray{i}=p;
getPosition(p)
end
When I start to set points on the image I get results like [675.000 538.000], which means that the x part of the coordinate is 675 and the y part is 538, right? This is what the MATLAB documentation says, but since the image is 576*120 (as displayed in the window) this is not logical.
It seemed to me like, somehow, getPosition returns the y coordinate first. I need some clarification on this.
Thanks for help
I just tried running your code in MATLAB 7.8.0 (R2009a) and had no problems with image sizes of either 576-by-120 or 120-by-576 (I was unsure which orientation you were using). If I left click inside the image, it places a new movable point. It did not allow me to place any points outside the image.
One small bug I found was that if you left-click in the image, then drag the mouse pointer outside the image while still holding the left button down, it will place the movable point outside the image and won't display it, displaying a set of coordinates that are not clipped to the axes rectangle.
I'm not sure of what could be your problem. Perhaps it's a bug with whatever MATLAB version you are using. I would suggest either restarting MATLAB, or clearing all variables from the workspace (except for the image data im).
Might be worth checking to see which renderer you are using (Painter or OpenGL), a colleague showed me some wierd behaviour with point picking when using the OpenGL renderer which went away when using the Painter renderer.
Your code uses the Image Processing Toolbox, which I don't have, so this is speculation. The coordinate system is probably set to the figure window (or maybe even the screen), not the image.
To test this, try clicking points outside the image to see if you can find the origin.