Extracting blue objects of interest
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Izuru on 24 Mar 2015
Commented: Image Analyst on 24 Mar 2015
I have an image of a circuit board with very blue chips. I want to display the blue chips as blue and display the rest of the board in greyscale.
My approach so far is:
image = imread('board.tif');
redBand = image(:,:,1); greenBand = image(:,:,2); blueBand = image(:,:,3);
After this I want to get everything in greyscale but display the blue chips on the same image. I think I have to put a red and green mask but I'm unsure how to do this. Any insights?
Christiaan on 24 Mar 2015
I made a code for you, where first the color 'blue' is detected at a certain threshold. (here 200) Then with a for loop, all points where the color is below the threshold are neglected. The image I used has been put in the attachment.
clc; clear all; close all;
% Read standard MATLAB demo image.
rgbImage = imread('board.jpg');
% Display the original image.
subplot(1, 3, 1);
title('Original RGB Image');
% Maximize figure.
set(gcf, 'Position', get(0, 'ScreenSize'));
% Split into color bands.
redBand = rgbImage(:,:, 1);
greenBand = rgbImage(:,:, 2);
blueBand = rgbImage(:,:, 3);
% Display them.
subplot(1, 3, 2);
% here objects which are parly blue make totaly blue
% here objects which are not blue to dark
% Display them.
subplot(1, 3, 3);
im = cat(3,redBand,greenBand,blueBand);
A second possibility would be using a tool from the File Exchange. A nice feature is 'imoverlay'. If you call this tool by writing in the prompt : >>imoverlay_tool and then use as a background 'blueband' (0-255), in the foreground'blueband' (200-250) and in the overlay (alpha 0.8) you obtain a figure that is blue where the objects are blue and the rest is gray.
Good luck! Christiaan
You can use my demos that find specified colors. Try the delta E one, or the one that does it in HSV color space.
Change the thresholds in the HSV one to get blue instead of yellow. For the delta E demo, you don't need to do that because you give it an example of the color you want to find by tracing a small region.
Find more on Image Processing Toolbox in Help Center and File Exchange
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