Outline the shape in the image

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Hassan Strong
Hassan Strong 2020-5-31
评论： Image Analyst 2021-8-31
Hi,
I need to outline a shape with circle in the image. Here is the image which i created using colormap.
The condition is if the 0.6<pixel<1 , then outline it with a circle. where pixel is the pixel value which is ranged from 0.1 to 1.
Here is the image info
Filename: XXXXX
FileModDate: '31-May-2020 23:43:42'
FileSize: 1588399
Format: 'tif'
FormatVersion: []
Width: 840
Height: 630
BitDepth: 24
ColorType: 'truecolor'
FormatSignature: [73 73 42 0]
ByteOrder: 'little-endian'
NewSubFileType: 0
BitsPerSample: [8 8 8]
Compression: 'Uncompressed'
PhotometricInterpretation: 'RGB'
StripOffsets: [1×70 double]
SamplesPerPixel: 3
RowsPerStrip: 9
StripByteCounts: [1×70 double]
XResolution: 96
YResolution: 96
ResolutionUnit: 'Inch'
Colormap: []
PlanarConfiguration: 'Chunky'
TileWidth: []
TileLength: []
TileOffsets: []
TileByteCounts: []
Orientation: 1
FillOrder: 1
GrayResponseUnit: 0.0100
MaxSampleValue: [255 255 255]
MinSampleValue: [0 0 0]
Thresholding: 1
Offset: 1587608
ImageDescription: 'MATLAB Handle Graphics'

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采纳的回答

Image Analyst
Image Analyst 2020-6-1
You can use bwboundaries() and plot():
binaryImage = 0.6 < grayImage & grayImage < 1;
boundaries = bwboundaries(binaryImage);
hold on;
for k = 1 : length(boundaries)
thisBoundary = boundaries{k};
x = thisBoundary(:, 2); % Column
y = thisBoundary(:, 1); % Row
plot(x, y, 'r-', 'LineWidth', 2);
end
Attach your array or image file if you need more help.
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Alex Perrakis
Alex Perrakis 2021-8-31
Hey, is there a way to plot those lines in normal plot with x-y-coordinates? i have your solution and i have found very good success thanks
Image Analyst
Image Analyst 2021-8-31
@Alex Perrakis, yes, simply bring up a new axes - one that does not have an image it in already - and call the same code
binaryImage = 0.6 < grayImage & grayImage < 1;
boundaries = bwboundaries(binaryImage);
figure; % Create a new figure.
for k = 1 : length(boundaries)
thisBoundary = boundaries{k};
x = thisBoundary(:, 2); % Column
y = thisBoundary(:, 1); % Row
plot(x, y, 'r-', 'LineWidth', 2);
end
grid on;

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更多回答（1 个）

Codeshadow
Codeshadow 2020-6-1
编辑：Codeshadow 2020-6-1
You could try using contourf and specify the contour levels as an input argument.
For example:
% Create an example mesh
x = linspace(-1, 1, 100);
y = x;
[X, Y] = meshgrid(x, y);
% Compute the radii
R = sqrt(X.^2 + Y.^2);
% Generate contour map, with levels in increments of 0.1 or at a fixed value
% level = [0:0.1:1];
level = [0.6 0.6];
contourf(X, Y, R, level)
colorbar();
xlabel('X')
ylabel('Y');
Replace R used above with your data.
Note: You might not be placing a circle around your data, but will instead be tracing the isolines at the levels you desire.
Hope this helps!
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Codeshadow
Codeshadow 2020-6-1
Apologies, I'd made a typo in my original answer, and have fixed it now.
When specifying a single level in the contourf function, you will need to pass it in as a vector of two identical values, such as [0.6 0.6] in the corrected code above. If you want to plot several levels, you can specify all levels in a vector (see commented code).
For the example of the circle, if you specify a level as [0.6 0.6], you will get something like
You can use the Key-Value pair argument ('ShowText', 'on') to mark the levels if you'd like.

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