Segmenting Part of the image using threshold

Question

Im trying to isolate and segment the yellow car body to change the color of it. in order to do that i need to separately identify the body from the image. And continue oration with the remaining white pixels. And im using C#, here the plan

Color d;
Color newColor = Color.YellowGreen;    
for(inti =0;i<carimage.Width;i++){
    for(intj =0;j<carimage.Height;j++){
        d = carimage.GetPixel(i, j);
            if(d.R == 255 && d.G==255 && d.B == 255)
                image.SetPixel(i, j, newColor );
    }
}

simple thresholding will trow the second image where car body is not separated correctly. i tried Aforge.net Fill holes image filter but no significant change has been done to the threshold image. I tried to use color filter but it i did not return a correct output due to color vary of the body. can anyone suggest and solution for this?

Original Image

original image

Threshold Image

threshold image

Please post the actual code. This code is obviously not the code you actually have in your program, since you have contracted `int i` into `inti`, which won't compile. Also, the code posted would, if corrected, replace the color white with the color green. The images suggests you're doing something else. Please post a coherent question. — Lasse V. Karlsen, Nov 14 '11 at 21:39

Niki · Answer 1 · 2011-11-15T13:33:01.747

Instead of thresholding, you might want to look into clustering.

As a quick&dirty test, I've increased the image brightness in HSB space (using Mathematica):

brightnessAdjusted = Image[ Map[#^{1, 1, 0.2} &, ImageData[ColorConvert[img, "HSB"]], {2}], ColorSpace -> "HSB"]

enter image description here

Then I've used simple K-Nearest clustering:

(clusters = ClusteringComponents[ColorConvert[brightnessAdjusted, "RGB"], 3, Method -> "KMeans"]) // Colorize

enter image description here

to find clusters of similar colors in the image (there are many more, probably more suitable clustering algorithms, so you should experiment a little). Then I can just adjust the color in one of the clusters:

Image[MapThread[If[#1 == 2, #2[[{1, 3, 2}]], #2] &, {clusters, ImageData[brightnessAdjusted]}, 2]]

enter image description here

If you want to use thresholding, you should probably use a CIE color space, since euclidian distances in that color space are closer to human perception.

score 0 · Answer 2 · edited Jun 20 '20 at 09:12

0

    I=imread('test.jpg'); 
    I=im2double(rgb2gray(I)); 
    BW=im2bw(I,0.64);imshow(BW)

Gives me :

I got the 0.64 threshold by looking at the image's histogram. I suggest you use MATLAB to do image processing as it is much easier. Hope that helps you in colouring the image.

edited Jun 20 '20 at 09:12

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answered Dec 09 '12 at 00:26

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score 0 · Answer 3 · answered Nov 15 '11 at 00:14

I had a similar project few years ago. I can't remember the exact details, but the idea was to shift a (not too small) sliding window over the image, and calculate the average intensity (maybe for R, G and B separately) inside the window at each position. I filled a "threshold image" with these averages, and subtracted it from the original image. There was a scaling factor somewhere, and other tuning stuff, but the point is, such an approach was way better than using a constant threshold.

score 0 · Answer 4 · edited May 23 '17 at 10:32

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If you are going to use a set of thresholds, you might be better of selecting yellow hues in the Hue Saturation Value colorspace. See the related SO question.

edited May 23 '17 at 10:32

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answered Nov 15 '11 at 11:18

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Segmenting Part of the image using threshold

Original Image

Threshold Image

4 Answers4