using numpy.any to match color in opencv gives strange results

» python » using numpy.any to match color in opencv gives strange results

By : Richard Gardner

Date : December 05 2020, 12:22 PM

it should still fix some issue You Don't need to over-complicate the problem by using numpy operations thrice. You may simply use cv2.inRange() and cv2.countNonZero() to get your job done. The above steps can be modulated to a method which you may call from your while loop to process each webcam frame.

code :

import cv2

def detect_color_blob(img_BGR, blob_color_BGR, tolerance, threshold):
    blob_color_lower = [blob_color_BGR[0] - tolerance, blob_color_BGR[1] - tolerance, blob_color_BGR[2] - tolerance]
    blob_color_upper = [blob_color_BGR[0] + tolerance, blob_color_BGR[1] + tolerance, blob_color_BGR[2] + tolerance]

    # Get a Binary Mask, where 255 => blob color found and 0=> blob color NOT found
    mask = cv2.inRange(img_BGR, blob_color_lower, blob_color_upper)

    # Check if the detected number of pixels is greater than threshold.
    return cv2.countNonZero(mask) > threshold

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Strange OpenCV Distance Transform Results

By : moin

Date : March 29 2020, 07:55 AM

wish help you to fix your issue One quick way to test your theory: try with a grey scale image that's muted (all values v --> 128+(v-128)/32 or something) and see if that makes the bands much wider or eliminates them completely.
It's always a good idea to nail down what the problem is first, and then try to fix it.

opencv zoom function strange results

By : jack903

Date : March 29 2020, 07:55 AM

Any of those help cv.Resize requires source and destination to be separate memory locations.
Now in the first snippet of your code, you are using cv.GetSubRect to generate an object pointing to area of image which you wish to zoom in. Here the new object is NOT pointing to a new memory location. It is pointing to a memory location which is a subset of original object.

How to pass a numpy ndarray as a color in OpenCV?

By : Alexander Sadovnikov

Date : March 29 2020, 07:55 AM

wish of those help I am trying to pass a ndarray into this line: cv2.fillPoly(im, pts=[cnt],color=(centroid_color[0],centroid_color[1],centroid_color[2])) , You can pass a numpy array directly as color argument like this:

code :

import numpy as np
import cv2

pts = np.array([[[10,40], [70,16], [100,90] ]], np.int32)
im = np.zeros([240,320, 3], np.uint8)
color = np.array((60,0,255))
cv2.fillPoly( im, pts, color)


cv2.imshow(" ", im)
cv2.waitKey(1)

clr = np.array([255, 0, 128])
cv2.fillPoly( im, pts, color=(clr[0], clr[1], clr[2]))

centroid_color = centroid_color.astype(np.int32, copy=False)

Opencv python HoughLinesP strange results

By : useryl

Date : March 29 2020, 07:55 AM

this will help NOTE: Since you linked a tutorial for OpenCV 2.4.x, I initially assumed you also wrote your code with OpenCV 2.4.11. As it turns out, you're actually using OpenCV 3.x. Keep in mind that there are subtle changes in the API between 2.x and 3.x.

code :

cv2.HoughLinesP(image, rho, theta, threshold[, lines[, minLineLength[, maxLineGap]]]) → lines

lines = cv2.HoughLinesP(cannied, rho=1, theta=np.pi / 180
    , threshold=80, lines=30, minLineLength=10)

lines = cv2.HoughLinesP(cannied, rho=1, theta=np.pi / 180
    , threshold=80, minLineLength=30, maxLineGap=10)

cv2.Canny(image, threshold1, threshold2[, edges[, apertureSize[, L2gradient]]]) → edges

cannied = cv2.Canny(img, threshold1=50, threshold2=200, edges=3)

cannied = cv2.Canny(img, threshold1=50, threshold2=200, apertureSize=3)

import cv2
import numpy as np


def get_lines(lines_in):
    if cv2.__version__ < '3.0':
        return lines_in[0]
    return [l[0] for l in lines]


img = cv2.imread('building.jpg')
img_gray = gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

cannied = cv2.Canny(img_gray, threshold1=50, threshold2=200, apertureSize=3)
lines = cv2.HoughLinesP(cannied, rho=1, theta=np.pi / 180, threshold=80, minLineLength=30, maxLineGap=10)

for line in get_lines(lines):
    leftx, boty, rightx, topy = line
    cv2.line(img, (leftx, boty), (rightx,topy), (255, 255, 0), 2)

cv2.imwrite('lines.png',img)
cv2.imwrite('canniedHouse.png',cannied)
cv2.waitKey(0)
cv2.destroyAllWindows()