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ViewsHow do I remove the dots / noise without damaging the text?
I'm processing the images with OpenCV and Python. I need to remove the dots / noise from the image.
I tried dilation which made the dots smaller, however the text is being damaged. I also tried looping dilation twice and erosion once. But this did not give satisfactory results.
Is there some other way I can achieve this?
Thank you :)
EDIT:
I'm new to image processing. My current code is as follows
image = cv2.imread(file)
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
kernel = np.ones((2, 2), np.uint8)
gray = cv2.GaussianBlur(gray, (5, 5), 0)
gray = cv2.GaussianBlur(gray, (5, 5), 0)
gray = cv2.adaptiveThreshold(gray, 255, cv2.ADAPTIVE_THRESH_GAUSSIAN_C, cv2.THRESH_BINARY, 11, 2)
gray = cv2.erode(gray, kernel, iterations=1)
gray = cv2.dilate(gray, kernel, iterations=1)
cv2.imwrite(file.split('.'[0]+"_process.TIF", gray))
EDIT 2:
I tried median blurring. It has solved 90% of the issue. I had been using gaussianBlurring all this while.
Thank you
1 answers
Answer question0
How about removing small connected components using connectedComponentsWithStats
import cv2
import numpy as np
img = cv2.imread('path_to_your_image', 0)
_, blackAndWhite = cv2.threshold(img, 127, 255, cv2.THRESH_BINARY_INV)
nlabels, labels, stats, centroids = cv2.connectedComponentsWithStats(blackAndWhite, None, None, None, 8, cv2.CV_32S)
sizes = stats[1:, -1] #get CC_STAT_AREA component
img2 = np.zeros((labels.shape), np.uint8)
for i in range(0, nlabels - 1):
if sizes[i] >= 50: #filter small dotted regions
img2[labels == i + 1] = 255
res = cv2.bitwise_not(img2)
cv2.imwrite('res.png', res)
And here is c++ example:
Mat invBinarized;
threshold(inputImage, invBinarized, 127, 255, THRESH_BINARY_INV);
Mat labels, stats, centroids;
auto nlabels = connectedComponentsWithStats(invBinarized, labels, stats, centroids, 8, CV_32S, CCL_WU);
Mat imageWithoutDots(inputImage.rows, inputImage.cols, CV_8UC1, Scalar(0));
for (int i = 1; i < nlabels; i++) {
if (stats.at<int>(i, 4) >= 50) {
for (int j = 0; j < imageWithoutDots.total(); j++) {
if (labels.at<int>(j) == i) {
imageWithoutDots.data[j] = 255;
}
}
}
}
cv::bitwise_not(imageWithoutDots, imageWithoutDots);
EDIT:
See also
OpenCV documentation for connectedComponentsWithStats
How to use openCV's connected components with stats in python