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I am trying to flip over the colorbar of my Heatmap in Seaborn.
Here is how it looks at the moment.
What I would like to have is the colorbar starting from the top
with the value 0 (Green) and going to the bottom with the value 8 (red).
Please note that the Y-axis points are sorted based on the average values
from min (top) to max (bottom) and I would like to keep them this way.
Any idea if it is possible to do that?
Here is an example of the current code:
cmap1 = mcolors.LinearSegmentedColormap.from_list("n",['#00FF00','#12FF00','#24FF00','#35FF00','#47FF00','#58FF00','#6AFF00','#7CFF00','#8DFF00','#9FFF00','#B0FF00','#C2FF00','#D4FF00','#E5FF00','#F7FF00','#FFF600','#FFE400','#FFD300','#FFC100','#FFAF00','#FF9E00','#FF8C00','#FF7B00','#FF6900','#FF5700','#FF4600','#FF3400','#FF2300','#FF1100','#FF0000',])
plt.figure(figsize=(22, 12))
df = pd.DataFrame( AgainReorderindSortedEDPList, index=sortedProgrammingLanguagesBasedOnAverage, columns=sortedTasksBasedOnAverage)
mask = df.isnull()
sns.heatmap(df, annot=True, fmt="g", cmap=cmap1, mask=mask)
plt.yticks(fontsize = 12)
plt.yticks(rotation=0)
plt.xticks(fontsize = 11)
plt.ylabel('Programming Languages', size = 15)
plt.xlabel('Programming Tasks', size = 15)
plt.xticks(rotation=-45)
plt.show()
The AgainReorderindSortedEDPList, sortedProgrammingLanguagesBasedOnAverage, and sortedTasksBasedOnAverage
are the data I am using to plot this heatmap.
You simply need to call invert_yaxis() on the axes that contain the colorbar. How to do that depends a bit on how you are creating your heatmap, but unfortunately you have not provided your code.
Here is the most simple example:
uniform_data = np.random.rand(10, 12)
ax = sns.heatmap(uniform_data)
plt.gcf().axes[1].invert_yaxis()
plt.gcf() gets a reference to the current figure. Figure.axes is a list of axes in the figure. axes[1] is the second axes, which should correspond to the axes created by heatmap to plot the colorbar.
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.
How can I change the values of the R, G and B in an image manually using MATLAB?
The computation for a green color enhancement needs to be done so how do we access and change the values of RGB using MATLAB?
Assuming you are using imread to read in the image, an RGB image is stored as an M x N x 3 matrix, where M,N are the rows and columns of the image. This is essentially a 3D matrix, where each colour plane is in a particular dimension. The red plane is the first of the third dimensions, the green plane is the second, and the blue plane is the third. As such, you can do something like:
im = imread('onion.png'); % // Built-in to MATLAB
red = im(:,:,1); %// Red channel
green = im(:,:,2); % // Green channel
blue = im(:,:,3); % // Blue channel
You can also merge the planes back by doing: im2 = cat(3, red, green, blue); Now, you can manipulate any of these planes by themselves. If you want to grab a subset of the image, you can do:
imSubset = im(row1:row2, col1:col2, :);
This will grab all pixels between rows row1 to row2 and columns col1 to col2. You can then split up the image into their corresponding planes.
Now, if you want to manually change pixels, you simply access whichever rows and columns you want in each of the planes and set them to whatever you want. For example, if you wanted to set a particular region in your image to all yellow pixels, you can do this:
im(1:50,1:50,1) = 0;
im(1:50,1:50,2) = 255;
im(1:50,1:50,3) = 255;
imshow(im);
This should place a yellow square of 50 pixels wide in the top left corner. You can also do the subset approach by:
imSubset = im(1:50,1:50,:); %// Extract
imSubset(:,:,1) = 0; %// Set
imSubset(:,:,2) = 255;
imSubset(:,:,3) = 255;
im(1:50,1:50,:) = imSubset; %// Place back
If I can be a shameless promoter, take a look at my Introduction to Digital Image Processing using MATLAB slides - http://www.slideshare.net/rayryeng1/introduction-to-digital-image-processing-using-matlab
Good luck!
I have an image with size 240*320 and I have the optical flow result with vertical and horizontal values. I need to visualize Optical flow by arrows on original image. I know that I have to use quiver function. Something like:
imshow(image)
hold on
quiver(vx,vy)
hold off
But what I get is a blue square instead of quivers.
An entirely blue square is probably caused by way too many arrows plotted close together.
For example, the following code will produce an easy-to-see (if not very meaningful) set of arrow:
figure
data = imread('peppers.png');
imshow(data)
s = size(data);
hold on
[x,y] = meshgrid(1:50:s(2),1:50:s(1));
px = cos(x);
py = sin(y);
quiver(x,y,px,py)
And this will produce an entirely blue plot:
figure
data = imread('peppers.png');
imshow(data)
s = size(data);
hold on
[x,y] = meshgrid(1:1:s(2),1:1:s(1)); % arrow spacing is too close!
px = cos(x);
py = sin(y);
quiver(x,y,px,py)
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)