How to detect colored patches in an image using OpenCV?

by

To process the colorful image in HSV color-space is a good direction. And I split the channels and find the S channel is great. Because S is Saturation(饱和度) of color.

enter image description here

Then threshold the S with thresh of 100, you will get this.
enter image description here

It will be easy to separate the colorful region in the threshed binary image.

As @Mark suggest, we can use adaptive thresh other than the fixed one. So, add THRESH_OTSU in the flags.

Core python code is presented as follow:

##(1) read into  bgr-space
img = cv2.imread("test.png")

##(2) convert to hsv-space, then split the channels
hsv = cv2.cvtColor(img, cv2.COLOR_BGR2HSV)
h,s,v = cv2.split(hsv)

##(3) threshold the S channel using adaptive method(`THRESH_OTSU`)  
th, threshed = cv2.threshold(s, 100, 255, cv2.THRESH_OTSU|cv2.THRESH_BINARY)

##(4) print the thresh, and save the result
print("Thresh : {}".format(th))
cv2.imwrite("result.png", threshed)


## >>> Thresh : 85.0

enter image description here

Related answers:

  1. Detect Colored Segment in an image
  2. Edge detection in opencv android
  3. OpenCV C++/Obj-C: Detecting a sheet of paper / Square Detection

More Related Contents:

  1. How to define the markers for Watershed in OpenCV?
  2. How to crop away convexity defects?
  3. Multi otsu(multi-thresholding) with openCV
  4. How to detect ellipses in image without using fitEllipse() in opencv?
  5. opencv c++ Edge detection to find edge that the top of it is white and the bottom is black
  6. Choosing the correct upper and lower HSV boundaries for color detection with`cv::inRange` (OpenCV)
  7. Simple and fast method to compare images for similarity
  8. How to define a threshold value to detect only green colour objects in an image with Python OpenCV?
  9. CV – Extract differences between two images
  10. Removing Horizontal Lines in image (OpenCV, Python, Matplotlib)
  11. Segmenting License Plate Characters
  12. Inverting a real-valued index grid
  13. connected components in OpenCV
  14. Automatic contrast and brightness adjustment of a color photo of a sheet of paper with OpenCV
  15. Convert RGB to Black & White in OpenCV
  16. Converting an OpenCV Image to Black and White
  17. OpenCV template matching and transparency
  18. Detect text area in an image using python and opencv
  19. OpenCV / SURF How to generate a image hash / fingerprint / signature out of the descriptors?
  20. Setting ROI with mouse from a rectangle on a video
  21. Combining Two Images with OpenCV
  22. Filling gaps in shape edges
  23. Pixel access in OpenCV 2.2
  24. Is Laplacian of Gaussian for blob detection or for edge detection?
  25. Irregular shape detection and measurement in python opencv
  26. OpenCV & Python – Image too big to display
  27. Add padding to images to get them into the same shape
  28. Are there any fast alternatives to SURF and SIFT for scale-invariant feature extraction?
  29. How is the camera coordinate system in OpenCV oriented?
  30. Preprocessing image for Tesseract OCR with OpenCV

Leave a Comment