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How to prevent INPAINTING blocks and improve coloring

I wanted to Remove all the texts USING INPAINTING from this IMAGE. I had been trying various methods, and eventually found that I can get the results through OCR and then using thresholding MASK THE IMAGE.
processedImage = preprocess(partOFimg)
mask = np.ones(img.shape[:2], dtype="uint8") * 255
for c in cnts:
cv2.drawContours(mask, [c], -1, 0, -1)
img = cv2.inpaint(img,mask,7,cv2.INPAINT_TELEA)
Preprocess operations:
ret,thresh1 = cv2.threshold(gray, 0, 255,cv2.THRESH_OTSU|cv2.THRESH_BINARY_INV)
rect_kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (15, 3))
dilation = cv2.dilate(thresh1, rect_kernel, iterations = 1)
edged = cv2.Canny(dilation, 50, 100)
cnts = cv2.findContours(edged.copy(), cv2.RETR_LIST, cv2.CHAIN_APPROX_SIMPLE)
cnts = imutils.grab_contours(cnts)
mask =
np.ones(img.shape[:2], dtype="uint8") * 255
When I run the above code, I here am the OUTPUT Image OUTPUT. As we can see, it is making some BLOCKS OF DIFFERENT COLOR over the IMAGE, I want to prevent that, How do I achieve this? I see that mask images are not formed well many times, and in cases when the text is white the PREPROCESSING doesn't occur properly.
How do I prevent these BLOCKS of other colours to FORM on the IMAGE?
Grayed Sub Image GRAYED
Threshold Sub IMG part: Thresholded Image
Masked Image Masked
EDIT 1:
I've managed to get this new better result by noticing that my threshold is the best mask I can get. After doing this I performed the masking process 3 different times with variable masks and inversions. I did the inpainting algorithm 3 times, it basically the other times inverse the mask, because in some cases required mask is the inversed mask. Still I think it needs improvement, If I chose a different image the results are not so good.

Python/OpenCV inpaint methods, generally, are not appropriate to your type of image. They work best on thin (scratch-like) regions, not large blocks. You really need an exemplar type method such as https://www.microsoft.com/en-us/research/wp-content/uploads/2016/02/criminisi_tip2004.pdf. But OpenCV does not have that.
However, the OpenCV methods do work here, I suspect, because you are filling with constant colors (green) and not texture. So you are best to try to get the mask of just the letters (characters), not rectangular blocks for the words. So, to show you what I mean, here is my Python/OpenCV approach.
Input:
Read the input
Threshold on the green sign
Apply morphology to close it up and keep as mask1
Apply the mask to the image to blacken out the outside of the sign
Threshold on the white in this new image and keep as mask2
Apply morphology dilate to enlarge it slightly and save as mask3
Do the inpaint
Save the results
import cv2
import numpy as np
# read input
img = cv2.imread('airport_sign.jpg')
# threshold on green sign
lower = (30,80,0)
upper = (70,120,20)
thresh = cv2.inRange(img, lower, upper)
# apply morphology close
kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (135,135))
mask1 = cv2.morphologyEx(thresh, cv2.MORPH_CLOSE, kernel)
# apply mask to img
img2 = img.copy()
img2[mask1==0] = (0,0,0)
# threshold on white
#gray = cv2.cvtColor(img2, cv2.COLOR_BGR2GRAY)
#mask2 = cv2.threshold(gray, 0, 255, cv2.THRESH_BINARY+cv2.THRESH_OTSU)[1]
lower = (120,120,120)
upper = (255,255,255)
mask2 = cv2.inRange(img2, lower, upper)
# apply morphology dilate
kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (5,5))
mask3 = cv2.morphologyEx(mask2, cv2.MORPH_DILATE, kernel)
# do inpainting
result1 = cv2.inpaint(img,mask3,11,cv2.INPAINT_TELEA)
result2 = cv2.inpaint(img,mask3,11,cv2.INPAINT_NS)
# save results
cv2.imwrite('airport_sign_mask.png', mask3)
cv2.imwrite('airport_sign_inpainted1.png', result1)
cv2.imwrite('airport_sign_inpainted2.png', result1)
# show results
cv2.imshow('thresh',thresh)
cv2.imshow('mask1',mask1)
cv2.imshow('img2',img2)
cv2.imshow('mask2',mask2)
cv2.imshow('mask3',mask3)
cv2.imshow('result1',result1)
cv2.imshow('result2',result2)
cv2.waitKey(0)
cv2.destroyAllWindows()
Mask 3:
Inpaint 1 (Telea):
Inpaint 2 (NS):

How to decide on the kernel to use for dilations (OpenCV/Python)?

I'm very new to OpenCV and recently, I'm trying to compare two images of rails, one with a train and one without. After the comparison, I apply a threshold, and there are some 'holes' in the white regions which I do not want. Currently, I am using dilation with 4 iterations and kernel set to "None", which defaults to a 3x3 by my understanding.
How do I decide what sort of kernel to use so that the dilation does a better job at making the white region continuous? Would also be nice if I could remove the small white blobs in the background. Here is the code:
resized = imutils.resize(img2, width=1050)
resized2 = imutils.resize(img3, width=1050)
grayA = cv2.cvtColor(resized, cv2.COLOR_BGR2GRAY)
grayB = cv2.cvtColor(resized2, cv2.COLOR_BGR2GRAY)
grayA = cv2.GaussianBlur(grayA,(7,7),0)
grayB = cv2.GaussianBlur(grayB,(7,7),0)
frameDelta = cv2.absdiff(grayA, grayB)
thresh = cv2.threshold(frameDelta, 20, 255, cv2.THRESH_BINARY)[1]
thresh = cv2.dilate(thresh, None, iterations=4)
Complete beginner in this, so even general tips/advice to improve these comparisons would be vastly appreciated!

Perhaps this will give you some idea about morphology in Python/OpenCV. First I use a square "open" kernel about the size of the small white spots to remove them. Then I use a horizontal rectangle "close" kernel about the size of the black gap to fill it. "Open" removes white regions (or fills black gaps) and close removes black regions (or fills white gaps)
Input:
import cv2
import numpy as np
# read image as grayscale
img = cv2.imread('blob3.png', cv2.IMREAD_GRAYSCALE)
# threshold to binary
thresh = cv2.threshold(img, 0, 255, cv2.THRESH_BINARY)[1]
# apply morphology open with square kernel to remove small white spots
kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (19,19))
morph1 = cv2.morphologyEx(thresh, cv2.MORPH_OPEN, kernel)
# apply morphology close with horizontal rectangle kernel to fill horizontal gap
kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (101,1))
morph2 = cv2.morphologyEx(morph1, cv2.MORPH_CLOSE, kernel)
# write results
cv2.imwrite("blob3_morph1.png", morph1)
cv2.imwrite("blob3_morph2.png", morph2)
# show results
cv2.imshow("thresh", thresh)
cv2.imshow("morph1", morph1)
cv2.imshow("morph2", morph2)
cv2.waitKey(0)
Morphology Square Open:
Morphology Rectangle Close:
Alternate Morphology Square Close:

How to remove noise in image OpenCV, Python?

I have some cropped images and I need images that have black texts on white background. Firstly I apply adaptive thresholding and then I try to remove noise. Although I tried a lot of noise removal techniques but when the image changed, the techniques I used failed.
The best method for converting image color to binary for my images is Adaptive Gaussian Thresholding. Here is my code:
im_gray = cv2.imread("image.jpg", cv2.IMREAD_GRAYSCALE)
image = cv2.GaussianBlur(im_gray, (5,5), 1)
th = cv2.adaptiveThreshold(image,255,cv2.ADAPTIVE_THRESH_GAUSSIAN_C,cv2.THRESH_BINARY,3,2)
I need smooth values, Decimal separator(dot) and postfix letters. How can I do this?

Before binarization, it is necessary to correct the nonuniform illumination of the background. For example, like this:
import cv2
image = cv2.imread('9qBsB.jpg')
image=cv2.cvtColor(image,cv2.COLOR_BGR2GRAY)
se=cv2.getStructuringElement(cv2.MORPH_RECT , (8,8))
bg=cv2.morphologyEx(image, cv2.MORPH_DILATE, se)
out_gray=cv2.divide(image, bg, scale=255)
out_binary=cv2.threshold(out_gray, 0, 255, cv2.THRESH_OTSU )[1]
cv2.imshow('binary', out_binary)
cv2.imwrite('binary.png',out_binary)
cv2.imshow('gray', out_gray)
cv2.imwrite('gray.png',out_gray)
Result:

You can do slightly better using division normalization in Python/OpenCV.
Input:
import cv2
import numpy as np
# load image
img = cv2.imread("license_plate.jpg")
# convert to grayscale
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
# blur
blur = cv2.GaussianBlur(gray, (0,0), sigmaX=33, sigmaY=33)
# divide
divide = cv2.divide(gray, blur, scale=255)
# otsu threshold
thresh = cv2.threshold(divide, 0, 255, cv2.THRESH_BINARY+cv2.THRESH_OTSU)[1]
# apply morphology
kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (3,3))
morph = cv2.morphologyEx(thresh, cv2.MORPH_CLOSE, kernel)
# write result to disk
cv2.imwrite("hebrew_text_division.jpg", divide)
cv2.imwrite("hebrew_text_division_threshold.jpg", thresh)
cv2.imwrite("hebrew_text_division_morph.jpg", morph)
# display it
cv2.imshow("gray", gray)
cv2.imshow("divide", divide)
cv2.imshow("thresh", thresh)
cv2.imshow("morph", morph)
cv2.waitKey(0)
cv2.destroyAllWindows()
Division Image:
Thresholded Image:
Morphology Cleaned Image:

Im assuming that you are preprocessing the image for OCR(Optical Character Recognition)
I had a project to detect license plates and these were the steps I did, you can apply them to your project. After greying the image try applying equalize histogram to the image, this allows the area's in the image with lower contrast to gain a higher contrast. Then blur the image to reduce the noise in the background. Next apply edge detection on the image, make sure that noise is sufficiently removed as ED is susceptible to it. Lastly, apply closing(dilation then erosion) on the image to close all the small holes inside the words.

Instead of erode and dilate, you can check this, that is basically both in one.
kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (1,2))
morphology_img = cv2.morphologyEx(img_grey, cv2.MORPH_OPEN, kernel,iterations=1)
plt.imshow(morphology_img,'Greys_r')
MORPHOLOGICAL_TRANSFORMATIONS

removing pixels less than n size(noise) in an image - open CV python

i am trying to remove noise in an image less and am currently running this code
import numpy as np
import argparse
import cv2
from skimage import morphology
# Construct the argument parser and parse the arguments
ap = argparse.ArgumentParser()
ap.add_argument("-i", "--image", required = True,
help = "Path to the image")
args = vars(ap.parse_args())
# Load the image, convert it to grayscale, and blur it slightly
image = cv2.imread(args["image"])
cv2.imshow("Image", image)
cv2.imwrite("image.jpg", image)
greenLower = np.array([50, 100, 0], dtype = "uint8")
greenUpper = np.array([120, 255, 120], dtype = "uint8")
green = cv2.inRange(image, greenLower, greenUpper)
#green = cv2.GaussianBlur(green, (3, 3), 0)
cv2.imshow("green", green)
cv2.imwrite("green.jpg", green)
cleaned = morphology.remove_small_objects(green, min_size=64, connectivity=2)
cv2.imshow("cleaned", cleaned)
cv2.imwrite("cleaned.jpg", cleaned)
cv2.waitKey(0)
However, the image does not seem to have changed from "green" to "cleaned" despite using the remove_small_objects function. why is this and how do i clean the image up? Ideally i would like to isolate only the image of the cabbage.
My thought process is after thresholding to remove pixels less than 100 in size, then smoothen the image with blur and fill up the black holes surrounded by white - that is what i did in matlab. If anybody could direct me to get the same results as my matlab implementation, that would be greatly appreciated. Thanks for your help.
Edit: made a few mistakes when changing the code, updated to what it currently is now and display the 3 images
image:
green:
clean:
my goal is to get somthing like this picture below from matlab implementation:

Preprocessing
A good idea when you're filtering an image is to lowpass the image or blur it a bit; that way neighboring pixels become a little more uniform in color, so it will ease brighter and darker spots on the image and keep holes out of your mask.
img = cv2.imread('image.jpg')
blur = cv2.GaussianBlur(img, (15, 15), 2)
lower_green = np.array([50, 100, 0])
upper_green = np.array([120, 255, 120])
mask = cv2.inRange(blur, lower_green, upper_green)
masked_img = cv2.bitwise_and(img, img, mask=mask)
cv2.imshow('', masked_img)
cv2.waitKey()
Colorspace
Currently, you're trying to contain an image by a range of colors with different brightness---you want green pixels, regardless of whether they are dark or light. This is much more easily accomplished in the HSV colorspace. Check out my answer here going in-depth on the HSV colorspace.
img = cv2.imread('image.jpg')
blur = cv2.GaussianBlur(img, (15, 15), 2)
hsv = cv2.cvtColor(blur, cv2.COLOR_BGR2HSV)
lower_green = np.array([37, 0, 0])
upper_green = np.array([179, 255, 255])
mask = cv2.inRange(hsv, lower_green, upper_green)
masked_img = cv2.bitwise_and(img, img, mask=mask)
cv2.imshow('', masked_img)
cv2.waitKey()
Removing noise in a binary image/mask
The answer provided by ngalstyan shows how to do this nicely with morphology. What you want to do is called opening, which is the combined process of eroding (which more or less just removes everything within a certain radius) and then dilating (which adds back to any remaining objects however much was removed). In OpenCV, this is accomplished with cv2.morphologyEx(img, cv2.MORPH_OPEN, kernel). The tutorials on that page show how it works nicely.
img = cv2.imread('image.jpg')
blur = cv2.GaussianBlur(img, (15, 15), 2)
hsv = cv2.cvtColor(blur, cv2.COLOR_BGR2HSV)
lower_green = np.array([37, 0, 0])
upper_green = np.array([179, 255, 255])
mask = cv2.inRange(hsv, lower_green, upper_green)
kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (15, 15))
opened_mask = cv2.morphologyEx(mask, cv2.MORPH_OPEN, kernel)
masked_img = cv2.bitwise_and(img, img, mask=opened_mask)
cv2.imshow('', masked_img)
cv2.waitKey()
Filling in gaps
In the above, opening was shown as the method to remove small bits of white from your binary mask. Closing is the opposite operation---removing chunks of black from your image that are surrounded by white. You can do this with the same idea as above, but using cv2.morphologyEx(img, cv2.MORPH_CLOSE, kernel). This isn't even necessary after the above in your case, as the mask doesn't have any holes. But if it did, you could close them up with closing. You'll notice my opening step actually removed a small bit of the plant at the bottom. You could actually fill those gaps with closing first, and then opening to remove the spurious bits elsewhere, but it's probably not necessary for this image.
Trying out new values for thresholding
You might want to get more comfortable playing around with different colorspaces and threshold levels to get a feel for what will work best for a particular image. It's not complete yet and the interface is a bit wonky, but I have a tool you can use online to try out different thresholding values in different colorspaces; check it out here if you'd like. That's how I quickly found values for your image.

Although, the above problem is solved using cv2.morphologyEx(img, cv2.MORPH_OPEN, kernel). But, if somebody wants to use morphology.remove_small_objects to remove area less than a specified size, for those this answer may be helpful.
Code I used to remove noise for above image is:
import numpy as np
import cv2
from skimage import morphology
# Load the image, convert it to grayscale, and blur it slightly
image = cv2.imread('im.jpg')
cv2.imshow("Image", image)
#cv2.imwrite("image.jpg", image)
greenLower = np.array([50, 100, 0], dtype = "uint8")
greenUpper = np.array([120, 255, 120], dtype = "uint8")
green = cv2.inRange(image, greenLower, greenUpper)
#green = cv2.GaussianBlur(green, (3, 3), 0)
cv2.imshow("green", green)
cv2.imwrite("green.jpg", green)
imglab = morphology.label(green) # create labels in segmented image
cleaned = morphology.remove_small_objects(imglab, min_size=64, connectivity=2)
img3 = np.zeros((cleaned.shape)) # create array of size cleaned
img3[cleaned > 0] = 255
img3= np.uint8(img3)
cv2.imshow("cleaned", img3)
cv2.imwrite("cleaned.jpg", img3)
cv2.waitKey(0)
Cleaned image is shown below:
To use morphology.remove_small_objects, first labeling of blobs is essential. For that I use imglab = morphology.label(green). Labeling is done like, all pixels of 1st blob is numbered as 1. similarly, all pixels of 7th blob numbered as 7 and so on. So, after removing small area, remaining blob's pixels values should be set to 255 so that cv2.imshow() can show these blobs. For that I create an array img3 of the same size as of cleaned image. I used img3[cleaned > 0] = 255 line to convert all pixels which value is more than 0 to 255.

It seems what you want to remove is a disconnected group of small blobs.
I think erode() will do a good job remove them with the right kernel.
Given an nxn kernel, erode moves the kernel through the image and replaces the center pixel by the minimum pixel in the kernel.
Then you can dilate() the resulting image to restore eroded edges of the green part.
Another option would be to use fastndenoising
##### option 1
kernel_size = (5,5) # should roughly have the size of the elements you want to remove
kernel_el = cv2.getStructuringElement(cv2.MORPH_RECT, kernel_size)
eroded = cv2.erode(green, kernel_el, (-1, -1))
cleaned = cv2.dilate(eroded, kernel_el, (-1, -1))
##### option 2
cleaned = cv2.fastNlMeansDenoisingColored(green, h=10)

How to take a threshold of only a part of the image with OTSU thresholding?

I'm using OTSU threshold on a dilated and eroded image as shown below:
k = np.ones((5,5),np.float32)/1
d = cv2.dilate(self.img, k, iterations=10)
e = cv2.erode(d, k, iterations=10)
self.thresh = cv2.threshold(e, 0, 255, cv2.THRESH_BINARY + cv2.THRESH_OTSU)[1]
This is the eroded and dilated image, and the one that gets thresholded:
I only want the circular bright region in the middle to be obtained from thresholding, but instead I'm getting this result:
How do I go about thresholding such that I only get the circular region in the middle, which also seems like the brightest (visually) part of the image?
Note: To avoid playing around with different values, I want to stick to OTSU thresholding, but I'm open to ideas.

You can use Dilate and Erode filters to this image, but in another order: Erode first and then Dialte. It will suppress bright areas from upper side of the image and threshold method will provide better result

You can try a gradient based approach. Below I've used the morphological gradient. I apply Otsu thresholding to this gradient image, followed by a similar amount of morphological closing (10 iterations), then take the morphological gradient of the resulting image.
Now the regions are easy to detect. You can filter the circular region from the contours, for example, using an area based approach: using bounding box dimensions of the contour, you can get an estimate of the radius, then compare the calculated area to the contour area.
Don't know how generic this approach would be for your collection.
Gradient image: intensity values scaled for visualization
Binarized gradient image
Closed image
Gradient
im = cv2.imread('LDxOj.jpg', 0)
kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (3, 3))
morph = cv2.morphologyEx(im, cv2.MORPH_GRADIENT, kernel)
_, bw = cv2.threshold(morph, 0, 255, cv2.THRESH_BINARY | cv2.THRESH_OTSU)
morph2 = cv2.morphologyEx(bw, cv2.MORPH_CLOSE, kernel, anchor = (-1, -1), iterations = 10)
morph3 = cv2.morphologyEx(morph2, cv2.MORPH_GRADIENT, kernel)