Legend for a image

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Shannon Cherry
Shannon Cherry 2018-8-16
评论： Ralph 2020-4-6
I'm a matlab newbie and plotting an image as shown below. I'm facing difficulties while adding a legend to image(); in my code. I could use legend when I use plot(); but could someone help me to use legend with image(); please.
% Display Data_1 and Data_2
DisplayData = zeros(100,100,length(Set));
DisplayData(Data_1_Index) = Data_1;
DisplayData(Data_2_Index) = Data_2;
DisplayData(Data_1_Index) = 20; % Use light blue for Data_1
DisplayData(Data_2_Index) = 50; % Use yellow for Data_2
figure;
image(DisplayData(:,:));
title('Data_1 and Data_2 elements');
Help command for legend was not that helpful.

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采纳的回答

Image Analyst
Image Analyst 2018-8-16
What exactly would you want to see as a legend for an image? If I want text up there explaining something I use either title() or text(). I think those should do what you want. Lines and markers, like you get with a line plot don't really apply for an image.
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Shannon Cherry
Shannon Cherry 2018-8-16
This works after removing the line
axis('on', 'image');
and I moved the text from position 1 to 12. However, I couldn't understand what axis(); was doing there. Below is the output with axis(); uncommented.
Output after commenting out axis(); looks good.
Image Analyst
Image Analyst 2018-8-16
axis('image') just makes it so that your image pixels are square. I thought you had used the XData option to scale your x axis, but I guess you didn't - your image is really only 14 pixels wide and 300 pixels tall so that's why it looks tall and narrow. If you don't use axis('image') then it will stretch your image in the x direction to give an image of a stretched, but more normal looking, aspect ratio.

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Nathan Jessurun
Nathan Jessurun 2019-10-31
编辑：Nathan Jessurun 2019-10-31
To me, this looks better. I store the colors in my image and make empty scatterplots on top of the image:
% Try it out
bwImg = imfill(imread('coins.png') > 100, 'holes');
% bwImg will have several binary circles
[eachCoin, numCoins] = bwlabel(bwImg);
% Get a different color for each coin. Add one for background and skip it
allColors = parula(numCoins + 1);
allColors = allColors(2:end,:);
labelsArr = cell(1, numCoins);
for ii = 1:length(labelsArr)
labelsArr{ii} = ['coin' num2str(ii)];
end
imagesc(eachCoin);
imlegend(allColors, labelsArr);
function imlegend(colorArr, labelsArr)
% For instance if two legend entries are needed:
% colorArr =
% Nx3 array of doubles. Each entry should be an RGB percentage value between 0 and 1
%
% labelsArr =
% 1×N cell array
% {'First name here'} {'Second name here'} {'etc'}
hold on;
for ii = 1:length(labelsArr)
% Make a new legend entry for each label. 'color' contains a 0->255 RGB triplet
scatter([],[],1, colorArr(ii,:), 'filled', 'DisplayName', labelsArr{ii});
end
hold off;
legend();
end
  1 个评论
Ralph
Ralph 2020-4-6
This is the best approach demonstrated. The task is not a legend for an 'image' per se, but rather for a 'map' with designated 2D regions.

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Haritha
Haritha 2018-8-16
try this,
if true
legend('image 1','image 2')
end

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