I am working with MATLAB for a school project. The assignment is to import a matrix file supplied to me, and display it as a new figure using image. Right now, I can make an image with
m1 = load('matrix1.csv'); image(m1)
But the image is rotated to the right. How do I rotate it so the image is presented horizontally rather than vertically?
Your issue is likely arising from the fact that there are different ways of storing data (row-major vs. column-major). In this case, your .csv file clearly is not in the format you are expecting. The easiest thing to do is to simply transpose the matrix containing your data:
m1 = m1';
image(m1);
If there is something crazier going on and this flips it the wrong way (I don't think this should be the case, but you never know), you can try the rotate command: http://www.mathworks.com/help/matlab/ref/rot90.html
Related
I'm currently working on an alignment script which aligns two images very well. Usually, I get a data set which contains over 50 images of cells. I normally calculate a transformation matrix (T) based on fluorescent beads. However, this T-matrix gave rise to polarization in unpolarized cells, indicating that the transformation is not optimal. Therefore I switched to another script, which calculates a T-matrix based on cells and not beads. This new T-matrix aligns almost perfectly for a fraction of the cells, but there is always a portion of the images which aligns not so good.
I would like to continue with the alignment on cells, because this script works much better than the alignment on beads. In order to have optimal T-matrix for each image, I would like to calculate unique T-matrices for each image couple. I'm not very skilled in Matlab so the solution I could think of did not work.
Below you can find the current script. It functions by creating variables of the images I want to align and assign them to im1 and im2 in the script:
function [T] = alim(im1, im2, Tstart)
%ALIM Determines the transformation between the cameras.
im3=im2;
if (nargin>2)
im2=imwarp(im2, Tstart,'OutputView',imref2d(size(im1)));
end
optimizer = registration.optimizer.RegularStepGradientDescent;
optimizer.MaximumIterations=500;
metric = registration.metric.MattesMutualInformation;
T = imregtform(im2, im1, 'affine', optimizer, metric);
if (nargin>2)
T.T=Tstart.T*T.T;
end
figure;
imshowpair(im1,imwarp(im3,T,'OutputView',imref2d(size(im1))));
end
I tried to incorporate a loop which imports all images from the folder sequentially and assign these to im1 and im2. However, the problems that arises is that the type of data changes from uint16 into cell, which can't be used for this type of transformation. One defines in the script the location of the folders 'CAM1' and 'CAM2' and the number of images in these folders ('imnum')
for i:imnum
x{i}=imread(strcat(link,'CAM1\',num2str(i),'.tif'));
y{i}=imread(strcat(link,'CAM2\',num2str(i),'.tif'));
I would like to have your view on this problem and hopefully you can make some suggestions on how I can import the images in a folder in one go and keep the data type uint16. I'm always open for suggestions so if you have other ideas on how to solve my problem, I would love it if you shared them with me. If anything is unclear, please contact me with questions!
With kind regards,
Reinier
x is a cell array, where each element x{i} is a uint16 array. Cell arrays can hold any other datatype, including more cell arrays, and are a great way to wrap collections of objects, especially when their sizes and/or types may differ.
In your case, just call your function like this:
T = alim(x{i}, y{i}, tstart);
Or, even better, put the output matrix into a similar cell:
T{i} = alim(x{i}, y{i}, tstart);
I'm very new to Matlab, though I know a few other programming languages, so please forgive me if this is something simple. I have not been able to find any answers to this, either on StackOverflow or elsewhere.
I produce a figure using the following code:
figure(6),imageplot(P); drawnow;
Which looks like this:
I then save this image to my computer using the following commands:
imwrite(P, 'images/plot.png');
And the resulting image is tiny, and missing some of the color information:
If, however, I utilize the save function in the open figure (image #1) and save it manually, I get exactly what I want, which is that exact image stored on my computer.
How would I program that? I assumed that imwrite() would just write the image directly, but apparently I'm doing something wrong. Any advice? Perhaps it has something to do with the imageplot command? I cannot seem to get that to work in imwrite.
Update: Based on the comments below, I have begun using "imresize" with the "nearest" option. This scales the image properly, but the resulting image is still curiously darker (and therefore has less information) than if I hit the "save" button in the figure.
Image saved from figure:
Image using "imresize" with "nearest" option:
The MATLAB imwrite command saves exactly the number of pixels as specified in your image matrix. This is the actual result of your computation; the reason the output is "tiny" is because it is supposed to be. To make it larger, would be to simply scale/zoom it as required.
The save figure option however does something quite different: it rasterizes the the output you obtain in the figure window and gives you the option for saving it as an image. This is evident in the fact that when you do so, you obtain a white background in addition to your result which is really just the grey background you see before you save it; this can be adjusted by resizing the figure window before utilizing the save option.
If you're looking to simply make the output figure larger, I would recommend using something along the lines of the imresize command.
Say, if you want the default size to be twice the size of the real result, simply use:
imresize(P, 2.0);
For more options, try help imresize.
The command you need for the "Save As..." functionality of figures is called "print". I often use
print(gcf, '-dpng', 'some_filename.png')
or
print(gcf, '-depsc', 'some_filename.eps','-r0')
to save a figure as it is shown on screen. The format png offers a small filesize and excellent quality, and it is understood by most image viewers and browsers. The eps format is a vector format, which I use for printig. The '-r0' option specifies "use the same size as given by the screen resolution" for the vector format properties.
So, I have a 512x512 distorted image, but what I'm trying to do is restore only a 400x400 centrally-positioned subsection of the image while it is still distorted outside of it. How do I go about implementing something like that?
I was thinking to have a for loop within a for loop like
for row = 57:457
for col = 57:457
%some filter in here
end
end
But I'm not quite sure what to do next...
As a general rule, you can do a lot of things in MATLAB without loops using vectorization instead. As discussed in the comments below your question, there are filtering functions included with MATLAB such as medfilt2, wiener2 or imfilter which all work on two-dimensional images directly without the need for any loops.
To restore only the center part of your image, you apply the filter to the full image, store the result in a temporary variable and then copy over the part that you want into your distored image:
tmpimage = medfilt2(distortedimage);
finalimage = distortedimage;
finalimage(57:456,57:456)=tmpimage(57:456,57:456);
Of course if you don't care about edge effects during the reconstruction, you can just call the reconstruction for the part that interests you and avoid the tmpimage:
finalimage = distortedimage;
finalimage(57:456,57:456)=medfilt2(distortedimage(57:456,57:456));
Note how the sizes in an assignment need to match: you can't assign finalimage(57:456,57:456)=medfilt2(distortedimage) since the right-hand-size produces a 512-by-512 matrix which doesn't fit into the 400-by-400 center of finalimage.
I want to write a code in matlab in which i would like to detect color objects in a given image and return the result as found the custom image or not found. i have an image of the custom object separately. im new to matlab... can anyone tell me how to proceed...
i have a pre defined image of an object say an lcd tv.... a given image which may or may not contain the object in it. i need a method to chek and find if the pre defined image is present or not in the given image... is it possible in matlab?
The I suggest you start researching. Stack Overflow is not a great place to ask such generalized questions.
1) Anything that you can do in any programming language is possible in matlab, you are limited by three things:
a) How fast do you want it to work
b) how much coding do you want to do
c) how much of your memory is matlab going to eatup
2) If I am understanding your question correctly you are: Looking to match an image that is fit inside a larger image
Solution: shift your image across the other image, calulate the difference between all the pixels. The set of pixels that is closest to your desired image should be zero.
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.