I used matlab code.
img = imread('cmap3.png')
map = jet(256)
ind = rgb2ind(img,map)
colormap(map)
cm = colormap('gray)
image(ind)
Through above code, I got the .
I want to save just the gray scale image without any graduations and numbers on x,y axis.
How do I remove them and save gray scale image?
If you use imwrite, you won't save the axes' labels.
For actual plots, there exists a different solutions, eg. described here: set the axis to start at the very left bottom corner so that there is no space left for descriptions: set(gca, 'Position',[0 0 1 1]). Than you can even use print to save the image/figure.
I am using the MATLAB function ginput to label my image data for further process. Here is my code:
file_name = "test.jpg";
% Read the image
img = imread(file_name);
% Get the image dimension
imgInfo = imfinfo(file_name);
width = imgInfo.Width;
height = imgInfo.Height;
% Using ginput function to label the image
figure(1);
imshow(img);
hold on;
[x, y] = ginput(4); % Manually label 4 points
scatter(x, y, 100, 'ro', 'filled'); % Plot the marked points on img
hold off;
My Problem:
I found that the output x and yare not integers, so they are not representing the pixel indices.
Sometimes, these two conditions max(x) > width and max(y) > height are satisfied. It seems to suggest that the 4 points I marked using ginput are outside the image (but actually it is not).
I am aware of this issue is related to Image Coordinate System setting, but I am still not sure how to convert x and y obtained from ginput function to the actual pixel indices?
Thanks.
The code below shows a 2x2 image, enlarges the axes so we can see it, then turns on the axes ticks and labels. What this does is allow you to see the coordinate system used to render images in an axes object.
imshow([255,0;0,255])
set(gca,'position',[0.2,0.2,0.6,0.6])
axis on
The coordinates returned by ginput match these coordinates.
In short, what you need to do is simply round the coordinates returned by ginput to get indices into the image:
[x, y] = ginput(4); % Manually label 4 points
x = round(x);
y = round(y);
I am trying to measure the distance two points on an image and then use that distance as an input for some other function.
Here is my code:
figure, imshow(I);
h = imdistline(gca);
api = iptgetapi(h);
width = api.getDistance();
When I run it, I am able to drag and get the distance I want on the image, but the distance I get from using the getDistance is some default value it started with , when it opened and it does not change , even if I change it in the image. How can the variable width have the distance i measured before I press enter or any eye and close the image.
Eric
You should wait with the getDistance() function:
% create random image
I = rand(100);
figure, imshow(I);
h = imdistline(gca);
api = iptgetapi(h);
% wait for key pressed
pause('on');
pause;
% get line
width = api.getDistance();
disp(width);
Now the image appears, you can move your distance measure, then focus matlab console and press any key to get the result.
Whilst using Matlab's GUIDE, I wish to plot a line onto an image. I managed to achieve this when I was using only one axis inside the GUI. However upon adding another axis the plot no longer overlays the image.
Initially the plot began to plot on the wrong axis and I realized I had forgotten to set the appropriate axis. However once I had selected the image axis for plotting on, the line which is to be plotted, doesn't lie on top of the image anymore, instead it just replaces the image with a graph of the line only.
My code:
imshow(img(k),'Parent',handles.display)
hold on
x1 = line(k).point1(1);
y1 = line(k).point1(2);
x2 = line(k).point2(1);
y2 = line(k).point2(2);
plot(handles.display,[x1 x2],[y1 y2],'Color','r','LineWidth', 2)
hold off
The code before I added the new axis was identical to above but with the handles.display parameter for the plot().
Any help would be greatly appreciated, thank you in advance.
When you call the HOLD function, you also need to specify the axis handle. Example:
%# create some axes
hAx1 = subplot(121);
hAx2 = subplot(122);
%# draw in first: image with line overlayed
I = imread('coins.png');
imshow(I, 'Parent',hAx1)
hold(hAx1,'on')
plot(hAx1, [1 100], [1 100], 'Color','r', 'LineWidth',2)
hold(hAx1,'off')
%# draw in second
surf(hAx2, peaks)
I have an image in MATLAB:
im = rgb2gray(imread('some_image.jpg');
% normalize the image to be between 0 and 1
im = im/max(max(im));
And I've done some processing that resulted in a number of points that I want to highlight:
points = some_processing(im);
Where points is a matrix the same size as im with ones in the interesting points.
Now I want to draw a circle on the image in all the places where points is 1.
Is there any function in MATLAB that does this? The best I can come up with is:
[x_p, y_p] = find (points);
[x, y] = meshgrid(1:size(im,1), 1:size(im,2))
r = 5;
circles = zeros(size(im));
for k = 1:length(x_p)
circles = circles + (floor((x - x_p(k)).^2 + (y - y_p(k)).^2) == r);
end
% normalize circles
circles = circles/max(max(circles));
output = im + circles;
imshow(output)
This seems more than somewhat inelegant. Is there a way to draw circles similar to the line function?
You could use the normal PLOT command with a circular marker point:
[x_p,y_p] = find(points);
imshow(im); %# Display your image
hold on; %# Add subsequent plots to the image
plot(y_p,x_p,'o'); %# NOTE: x_p and y_p are switched (see note below)!
hold off; %# Any subsequent plotting will overwrite the image!
You can also adjust these other properties of the plot marker: MarkerEdgeColor, MarkerFaceColor, MarkerSize.
If you then want to save the new image with the markers plotted on it, you can look at this answer I gave to a question about maintaining image dimensions when saving images from figures.
NOTE: When plotting image data with IMSHOW (or IMAGE, etc.), the normal interpretation of rows and columns essentially becomes flipped. Normally the first dimension of data (i.e. rows) is thought of as the data that would lie on the x-axis, and is probably why you use x_p as the first set of values returned by the FIND function. However, IMSHOW displays the first dimension of the image data along the y-axis, so the first value returned by FIND ends up being the y-coordinate value in this case.
This file by Zhenhai Wang from Matlab Central's File Exchange does the trick.
%----------------------------------------------------------------
% H=CIRCLE(CENTER,RADIUS,NOP,STYLE)
% This routine draws a circle with center defined as
% a vector CENTER, radius as a scaler RADIS. NOP is
% the number of points on the circle. As to STYLE,
% use it the same way as you use the rountine PLOT.
% Since the handle of the object is returned, you
% use routine SET to get the best result.
%
% Usage Examples,
%
% circle([1,3],3,1000,':');
% circle([2,4],2,1000,'--');
%
% Zhenhai Wang <zhenhai#ieee.org>
% Version 1.00
% December, 2002
%----------------------------------------------------------------
Funny! There are 6 answers here, none give the obvious solution: the rectangle function.
From the documentation:
Draw a circle by setting the Curvature property to [1 1]. Draw the circle so that it fills the rectangular area between the points (2,4) and (4,6). The Position property defines the smallest rectangle that contains the circle.
pos = [2 4 2 2];
rectangle('Position',pos,'Curvature',[1 1])
axis equal
So in your case:
imshow(im)
hold on
[y, x] = find(points);
for ii=1:length(x)
pos = [x(ii),y(ii)];
pos = [pos-0.5,1,1];
rectangle('position',pos,'curvature',[1 1])
end
As opposed to the accepted answer, these circles will scale with the image, you can zoom in an they will always mark the whole pixel.
Hmm I had to re-switch them in this call:
k = convhull(x,y);
figure;
imshow(image); %# Display your image
hold on; %# Add subsequent plots to the image
plot(x,y,'o'); %# NOTE: x_p and y_p are switched (see note below)!
hold off; %# Any subsequent plotting will overwrite the image!
In reply to the comments:
x and y are created using the following code:
temp_hull = stats_single_object(k).ConvexHull;
for k2 = 1:length(temp_hull)
i = i+1;
[x(i,1)] = temp_hull(k2,1);
[y(i,1)] = temp_hull(k2,2);
end;
it might be that the ConvexHull is the other way around and therefore the plot is different. Or that I made a mistake and it should be
[x(i,1)] = temp_hull(k2,2);
[y(i,1)] = temp_hull(k2,1);
However the documentation is not clear about which colum = x OR y:
Quote: "Each row of the matrix contains the x- and y-coordinates of one vertex of the polygon. "
I read this as x is the first column and y is the second colum.
In newer versions of MATLAB (I have 2013b) the Computer Vision System Toolbox contains the vision.ShapeInserter System object which can be used to draw shapes on images. Here is an example of drawing yellow circles from the documentation:
yellow = uint8([255 255 0]); %// [R G B]; class of yellow must match class of I
shapeInserter = vision.ShapeInserter('Shape','Circles','BorderColor','Custom','CustomBorderColor',yellow);
I = imread('cameraman.tif');
circles = int32([30 30 20; 80 80 25]); %// [x1 y1 radius1;x2 y2 radius2]
RGB = repmat(I,[1,1,3]); %// convert I to an RGB image
J = step(shapeInserter, RGB, circles);
imshow(J);
With MATLAB and Image Processing Toolbox R2012a or newer, you can use the viscircles function to easily overlay circles over an image. Here is an example:
% Plot 5 circles at random locations
X = rand(5,1);
Y = rand(5,1);
% Keep the radius 0.1 for all of them
R = 0.1*ones(5,1);
% Make them blue
viscircles([X,Y],R,'EdgeColor','b');
Also, check out the imfindcircles function which implements the Hough circular transform. The online documentation for both functions (links above) have examples that show how to find circles in an image and how to display the detected circles over the image.
For example:
% Read the image into the workspace and display it.
A = imread('coins.png');
imshow(A)
% Find all the circles with radius r such that 15 ≤ r ≤ 30.
[centers, radii, metric] = imfindcircles(A,[15 30]);
% Retain the five strongest circles according to the metric values.
centersStrong5 = centers(1:5,:);
radiiStrong5 = radii(1:5);
metricStrong5 = metric(1:5);
% Draw the five strongest circle perimeters.
viscircles(centersStrong5, radiiStrong5,'EdgeColor','b');
Here's the method I think you need:
[x_p, y_p] = find (points);
% convert the subscripts to indicies, but transposed into a row vector
a = sub2ind(size(im), x_p, y_p)';
% assign all the values in the image that correspond to the points to a value of zero
im([a]) = 0;
% show the new image
imshow(im)