Finding exact HSV values of colors

Question

this is my marker

Using cvInRangeS(hsvframe,cvScalar(90, 40, 50) and cvScalar(255, 90, 255),threshy), how can I get the exact range of values for each color (purple and yellow)?

I'm certain this is in the OpenCV sample, or tutorial code some place. A little app with sliders that you mess with untill you find the colour youre looking for. — j0h, Sep 06 '16 at 23:34
While searching for an answer to a similar problem, I found a perfect solution implemented in Python here: https://stackoverflow.com/questions/38877102/how-to-detect-red-color-in-opencv-python — anujonthemove, Sep 02 '20 at 13:08

score 1 · Answer 1 · answered Jul 04 '13 at 17:54

Use a color picker web-site to check out the hue values of them.

http://www.color-hex.com/color/eca314

http://www.color-hex.com/color/923ca7

Note that you need to transform the hue angle (0-360) between (0-255) range. Use inranges function for both colors and add the images:

cvInRangeS(hsvframe,cvScalar(20, 0, 0), cvScalar(30, 255, 255),threshorange);
cvInRangeS(hsvframe,cvScalar(200, 0, 0), cvScalar(210, 255, 255),threshpurple);
cvOr(threshorange, threshpurple, threshy);

orange : 12-25 purple : 143-162 try these. – baci Jul 05 '13 at 14:48 — baci, Jul 05 '13 at 14:48

score 1 · Answer 2 · edited Sep 14 '16 at 14:19

You might want to try this one:

Mat matSrcCopyForHSVColorDisplay, HSV_image_display;

//Make a copy of the original image
matSrcCopyForHSVColorDisplay = matSrc.clone(); 

//Convert RGB to HSV
cvtColor(matSrc, HSV_image_display, CV_BGR2HSV); 

//To access each pixel in the images we are using this syntax:
//image.at(y,x)[c] where y is the row, x is the column 
//and c is H, S or V (0, 1 or 2)
Vec3b p = HSV_image_display.at<Vec3b>(50, 10); //Vec3b - Array of 3 uchar numbers

//p[0] - H, p[1] - S, p[2] - V
printf(text, "H=%d, S=%d, V=%d", p[0], p[1], p[2]); 

//putText(matSrcCopyForHSVColorDisplay, text, Font_Position, 
//Font_Type, Font_Scale, Font_Colour, Font_Thickness); 
//Display the text
putText(matSrcCopyForHSVColorDisplay, text, center, 
        FONT_HERSHEY_COMPLEX_SMALL, 2, cvScalar(255, 0, 0), 1, CV_AA);

//Refresh the image
imshow("HSV Value", matSrcCopyForHSVColorDisplay); 
printf("H=%d, S=%d, V=%d\n", p[0], p[1], p[2]);

Finding exact HSV values of colors

2 Answers2