How to segment Blue color object on this images?

How to segment Blue color object on this images?

Answer 1

[Benjamin Kraus]

Do you have access to the Image Processing Toolbox? If so, check out these options:

• Color Thresholder
• Image Segmentation Using the Image Segmenter App
• Segmentation methods in image processing and analysis
• Image Segmentation

[Benjamin Kraus]

I played around with the Color Thresholder app, and it looks like it can do a pretty good job using either the HSV or LAB color space (really all the color spaces look good).

I created this script using the Color Thresholder app and the HSV color space:

function [BW,maskedRGBImage] = createMask(RGB)
%createMask  Threshold RGB image using auto-generated code from colorThresholder app.
%  [BW,MASKEDRGBIMAGE] = createMask(RGB) thresholds image RGB using
%  auto-generated code from the colorThresholder app. The colorspace and
%  range for each channel of the colorspace were set within the app. The
%  segmentation mask is returned in BW, and a composite of the mask and
%  original RGB images is returned in maskedRGBImage.

% Auto-generated by colorThresholder app on 29-Dec-2017
%------------------------------------------------------

% Convert RGB image to chosen color space
I = rgb2hsv(RGB);

% Define thresholds for channel 1 based on histogram settings
channel1Min = 0.500;
channel1Max = 0.727;

% Define thresholds for channel 2 based on histogram settings
channel2Min = 0.307;
channel2Max = 1.000;

% Define thresholds for channel 3 based on histogram settings
channel3Min = 0.000;
channel3Max = 1.000;

% Create mask based on chosen histogram thresholds
sliderBW = (I(:,:,1) >= channel1Min ) & (I(:,:,1) <= channel1Max) & ...
  (I(:,:,2) >= channel2Min ) & (I(:,:,2) <= channel2Max) & ...
  (I(:,:,3) >= channel3Min ) & (I(:,:,3) <= channel3Max);
BW = sliderBW;

% Initialize output masked image based on input image.
maskedRGBImage = RGB;

% Set background pixels where BW is false to zero.
maskedRGBImage(repmat(~BW,[1 1 3])) = 0;

end

[Benjamin Kraus]

This one, using the YCbCr color space works pretty well:

function [BW,maskedRGBImage] = createMask(RGB)
%createMask  Threshold RGB image using auto-generated code from colorThresholder app.
%  [BW,MASKEDRGBIMAGE] = createMask(RGB) thresholds image RGB using
%  auto-generated code from the colorThresholder app. The colorspace and
%  range for each channel of the colorspace were set within the app. The
%  segmentation mask is returned in BW, and a composite of the mask and
%  original RGB images is returned in maskedRGBImage.

% Auto-generated by colorThresholder app on 29-Dec-2017
%------------------------------------------------------

% Convert RGB image to chosen color space
I = rgb2ycbcr(RGB);

% Define thresholds for channel 1 based on histogram settings
channel1Min = 0.000;
channel1Max = 255.000;

% Define thresholds for channel 2 based on histogram settings
channel2Min = 157.000;
channel2Max = 255.000;

% Define thresholds for channel 3 based on histogram settings
channel3Min = 0.000;
channel3Max = 255.000;

% Create mask based on chosen histogram thresholds
sliderBW = (I(:,:,1) >= channel1Min ) & (I(:,:,1) <= channel1Max) & ...
  (I(:,:,2) >= channel2Min ) & (I(:,:,2) <= channel2Max) & ...
  (I(:,:,3) >= channel3Min ) & (I(:,:,3) <= channel3Max);
BW = sliderBW;

% Initialize output masked image based on input image.
maskedRGBImage = RGB;

% Set background pixels where BW is false to zero.
maskedRGBImage(repmat(~BW,[1 1 3])) = 0;

end

[Ilaria Sani]

Hi Benjamin, How did you create the script after playing around with the App?

Thanks, Ilaria

[Benjamin Kraus]

Ilaria,

1. Open the "Color Thresholder" app from the Image Processing Toolbox.
2. Load your image.
3. Select your color space.
4. Change the thresholds to your liking.
5. Click the drop-down menu (the downward pointing arrow) below the "Export" button and choose "Export Function".