Prasad9/add_gaussian_noise.py

liruoteng · 2019-01-24T05:14:22Z

where did you use the defined 'var' and 'sigma'?

b-hakim · 2019-03-08T09:25:49Z

it shall be:
gaussian = np.random.normal(mean,sigma,(row,col, 1))
instead of line #12:
gaussian = np.random.random((row, col, 1)).astype(np.float32)

b-hakim · 2019-03-08T10:05:40Z

Also Note that this is not adding gaussian noise, it adds a transparent layer to make the image darker (as if it is changing the lighting)

Adding gaussian noise shall looks like so:

import numpy as np
import cv2
img = cv2.imread(img_path)
mean = 0
var = 10
sigma = var ** 0.5
gaussian = np.random.normal(mean, sigma, (224, 224)) #  np.zeros((224, 224), np.float32)

noisy_image = np.zeros(img.shape, np.float32)

if len(img.shape) == 2:
    noisy_image = img + gaussian
else:
    noisy_image[:, :, 0] = img[:, :, 0] + gaussian
    noisy_image[:, :, 1] = img[:, :, 1] + gaussian
    noisy_image[:, :, 2] = img[:, :, 2] + gaussian

cv2.normalize(noisy_image, noisy_image, 0, 255, cv2.NORM_MINMAX, dtype=-1)
noisy_image = noisy_image.astype(np.uint8)

cv2.imshow("img", img)
cv2.imshow("gaussian", gaussian)
cv2.imshow("noisy", noisy_image)

cv2.waitKey(0)

xvdp · 2019-05-14T19:09:07Z

Depends what your goal is:
3 examples,

gaussian noise added over image: noise is spread throughout
gaussian noise multiplied then added over image: noise increases with image value
image folded over and gaussian noise multipled and added to it: peak noise affects mid values, white and black receiving little noise
in every case i blend in 0.2 and 0.4 of the image

import numpy as np
import cv2
import matplotlib.pyplot as plt

img = cv2.imread(img_path)[...,::-1]/255.0
noise =  np.random.normal(loc=0, scale=1, size=img.shape)

# noise overlaid over image
noisy = np.clip((img + noise*0.2),0,1)
noisy2 = np.clip((img + noise*0.4),0,1)

# noise multiplied by image:
# whites can go to black but blacks cannot go to white
noisy2mul = np.clip((img*(1 + noise*0.2)),0,1)
noisy4mul = np.clip((img*(1 + noise*0.4)),0,1)

noisy2mul = np.clip((img*(1 + noise*0.2)),0,1)
noisy4mul = np.clip((img*(1 + noise*0.4)),0,1)

# noise multiplied by bottom and top half images,
# whites stay white blacks black, noise is added to center
img2 = img*2
n2 = np.clip(np.where(img2 <= 1, (img2*(1 + noise*0.2)), (1-img2+1)*(1 + noise*0.2)*-1 + 2)/2, 0,1)
n4 = np.clip(np.where(img2 <= 1, (img2*(1 + noise*0.4)), (1-img2+1)*(1 + noise*0.4)*-1 + 2)/2, 0,1)


# norm noise for viz only
noise2 = (noise - noise.min())/(noise.max()-noise.min())
plt.figure(figsize=(20,20))
plt.imshow(np.vstack((np.hstack((img, noise2)),
                      np.hstack((noisy, noisy2)),
                      np.hstack((noisy2mul, noisy4mul)),
                      np.hstack((n2, n4)))))
plt.show()
plt.hist(noise.ravel(), bins=100)
plt.show()

xvdp · 2019-06-02T22:50:39Z

skimage has a few nice noise functions easy to compare, i like poisson, looks closest to film grain

import skimage
import matplotlib.pyplot as plt
img_path="https://i.guim.co.uk/img/media/4ddba561156645952502f7241bd1a64abd0e48a3/0_1251_3712_2225/master/3712.jpg?width=1920&quality=85&auto=format&fit=max&s=1280341b186f8352416517fc997cd7da"
img = skimage.io.imread(img_path)/255.0

def plotnoise(img, mode, r, c, i):
    plt.subplot(r,c,i)
    if mode is not None:
        gimg = skimage.util.random_noise(img, mode=mode)
        plt.imshow(gimg)
    else:
        plt.imshow(img)
    plt.title(mode)
    plt.axis("off")

plt.figure(figsize=(18,24))
r=4
c=2
plotnoise(img, "gaussian", r,c,1)
plotnoise(img, "localvar", r,c,2)
plotnoise(img, "poisson", r,c,3)
plotnoise(img, "salt", r,c,4)
plotnoise(img, "pepper", r,c,5)
plotnoise(img, "s&p", r,c,6)
plotnoise(img, "speckle", r,c,7)
plotnoise(img, None, r,c,8)
plt.show()

PallawiSinghal · 2019-10-12T16:08:48Z

skimage has a few nice noise functions easy to compare, i like poisson, looks closest to film grain

import skimage
import matplotlib.pyplot as plt
img_path="https://i.guim.co.uk/img/media/4ddba561156645952502f7241bd1a64abd0e48a3/0_1251_3712_2225/master/3712.jpg?width=1920&quality=85&auto=format&fit=max&s=1280341b186f8352416517fc997cd7da"
img = skimage.io.imread(img_path)/255.0

def plotnoise(img, mode, r, c, i):
    plt.subplot(r,c,i)
    if mode is not None:
        gimg = skimage.util.random_noise(img, mode=mode)
        plt.imshow(gimg)
    else:
        plt.imshow(img)
    plt.title(mode)
    plt.axis("off")

plt.figure(figsize=(18,24))
r=4
c=2
plotnoise(img, "gaussian", r,c,1)
plotnoise(img, "localvar", r,c,2)
plotnoise(img, "poisson", r,c,3)
plotnoise(img, "salt", r,c,4)
plotnoise(img, "pepper", r,c,5)
plotnoise(img, "s&p", r,c,6)
plotnoise(img, "speckle", r,c,7)
plotnoise(img, None, r,c,8)
plt.show()

awesome

quantshah · 2020-01-28T09:51:08Z

This is so cool. Thank you so much.

RehamMuhammad · 2020-04-25T18:31:24Z

Depends what your goal is:
3 examples,

gaussian noise added over image: noise is spread throughout
gaussian noise multiplied then added over image: noise increases with image value
image folded over and gaussian noise multipled and added to it: peak noise affects mid values, white and black receiving little noise
in every case i blend in 0.2 and 0.4 of the image

import numpy as np
import cv2
import matplotlib.pyplot as plt

img = cv2.imread(img_path)[...,::-1]/255.0
noise =  np.random.normal(loc=0, scale=1, size=img.shape)

# noise overlaid over image
noisy = np.clip((img + noise*0.2),0,1)
noisy2 = np.clip((img + noise*0.4),0,1)

# noise multiplied by image:
# whites can go to black but blacks cannot go to white
noisy2mul = np.clip((img*(1 + noise*0.2)),0,1)
noisy4mul = np.clip((img*(1 + noise*0.4)),0,1)

noisy2mul = np.clip((img*(1 + noise*0.2)),0,1)
noisy4mul = np.clip((img*(1 + noise*0.4)),0,1)

# noise multiplied by bottom and top half images,
# whites stay white blacks black, noise is added to center
img2 = img*2
n2 = np.clip(np.where(img2 <= 1, (img2*(1 + noise*0.2)), (1-img2+1)*(1 + noise*0.2)*-1 + 2)/2, 0,1)
n4 = np.clip(np.where(img2 <= 1, (img2*(1 + noise*0.4)), (1-img2+1)*(1 + noise*0.4)*-1 + 2)/2, 0,1)


# norm noise for viz only
noise2 = (noise - noise.min())/(noise.max()-noise.min())
plt.figure(figsize=(20,20))
plt.imshow(np.vstack((np.hstack((img, noise2)),
                      np.hstack((noisy, noisy2)),
                      np.hstack((noisy2mul, noisy4mul)),
                      np.hstack((n2, n4)))))
plt.show()
plt.hist(noise.ravel(), bins=100)
plt.show()

Thank you so much that was so helpful

Guardian99 · 2020-05-29T15:30:20Z

Depends what your goal is:
3 examples,

gaussian noise added over image: noise is spread throughout
gaussian noise multiplied then added over image: noise increases with image value
image folded over and gaussian noise multipled and added to it: peak noise affects mid values, white and black receiving little noise
in every case i blend in 0.2 and 0.4 of the image

import numpy as np
import cv2
import matplotlib.pyplot as plt

img = cv2.imread(img_path)[...,::-1]/255.0
noise =  np.random.normal(loc=0, scale=1, size=img.shape)

# noise overlaid over image
noisy = np.clip((img + noise*0.2),0,1)
noisy2 = np.clip((img + noise*0.4),0,1)

# noise multiplied by image:
# whites can go to black but blacks cannot go to white
noisy2mul = np.clip((img*(1 + noise*0.2)),0,1)
noisy4mul = np.clip((img*(1 + noise*0.4)),0,1)

noisy2mul = np.clip((img*(1 + noise*0.2)),0,1)
noisy4mul = np.clip((img*(1 + noise*0.4)),0,1)

# noise multiplied by bottom and top half images,
# whites stay white blacks black, noise is added to center
img2 = img*2
n2 = np.clip(np.where(img2 <= 1, (img2*(1 + noise*0.2)), (1-img2+1)*(1 + noise*0.2)*-1 + 2)/2, 0,1)
n4 = np.clip(np.where(img2 <= 1, (img2*(1 + noise*0.4)), (1-img2+1)*(1 + noise*0.4)*-1 + 2)/2, 0,1)


# norm noise for viz only
noise2 = (noise - noise.min())/(noise.max()-noise.min())
plt.figure(figsize=(20,20))
plt.imshow(np.vstack((np.hstack((img, noise2)),
                      np.hstack((noisy, noisy2)),
                      np.hstack((noisy2mul, noisy4mul)),
                      np.hstack((n2, n4)))))
plt.show()
plt.hist(noise.ravel(), bins=100)
plt.show()

Is there a way to add noise to the bottom half of the image?

xvdp · 2020-06-01T20:31:22Z

multiply it by a mask should do it.

…

On Fri, May 29, 2020 at 8:30 AM Kanishk Rana ***@***.***> wrote: ***@***.**** commented on this gist. ------------------------------ Depends what your goal is: 3 examples, - gaussian noise added over image: noise is spread throughout - gaussian noise multiplied then added over image: noise increases with image value - image folded over and gaussian noise multipled and added to it: peak noise affects mid values, white and black receiving little noise in every case i blend in 0.2 and 0.4 of the image import numpy as npimport cv2import matplotlib.pyplot as plt img = cv2.imread(img_path)[...,::-1]/255.0noise = np.random.normal(loc=0, scale=1, size=img.shape) # noise overlaid over imagenoisy = np.clip((img + noise*0.2),0,1)noisy2 = np.clip((img + noise*0.4),0,1) # noise multiplied by image:# whites can go to black but blacks cannot go to whitenoisy2mul = np.clip((img*(1 + noise*0.2)),0,1)noisy4mul = np.clip((img*(1 + noise*0.4)),0,1) noisy2mul = np.clip((img*(1 + noise*0.2)),0,1)noisy4mul = np.clip((img*(1 + noise*0.4)),0,1) # noise multiplied by bottom and top half images,# whites stay white blacks black, noise is added to centerimg2 = img*2n2 = np.clip(np.where(img2 <= 1, (img2*(1 + noise*0.2)), (1-img2+1)*(1 + noise*0.2)*-1 + 2)/2, 0,1)n4 = np.clip(np.where(img2 <= 1, (img2*(1 + noise*0.4)), (1-img2+1)*(1 + noise*0.4)*-1 + 2)/2, 0,1) # norm noise for viz onlynoise2 = (noise - noise.min())/(noise.max()-noise.min())plt.figure(figsize=(20,20))plt.imshow(np.vstack((np.hstack((img, noise2)), np.hstack((noisy, noisy2)), np.hstack((noisy2mul, noisy4mul)), np.hstack((n2, n4)))))plt.show()plt.hist(noise.ravel(), bins=100)plt.show() [image: image] <https://user-images.githubusercontent.com/40925114/57724968-81aa7e00-767b-11e9-9df4-94a89ca47c73.png> Is there a way to add noise to the bottom half of the image? — You are receiving this because you commented. Reply to this email directly, view it on GitHub <https://gist.github.com/28f6a2df8e8d463c6ddd040f4f6a028a#gistcomment-3322834>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AJYHPOXTVKJASPCK7CLRZRTRT7IJXANCNFSM4HM42OEQ> .

IrshadAhmedHanif · 2021-03-20T11:25:51Z

I have an issue in line 5..
'str' object has no attribute 'shape'
how can i solve this issue?

rajiv1990 · 2021-03-22T21:22:10Z

I have an issue in line 5..
'str' object has no attribute 'shape'

Appears like the parameter you have sent is a string.
You can try reading an image file by using cv2.imread() and send that to the function

santykish23 · 2022-03-01T05:07:18Z

Depends what your goal is: 3 examples,

* gaussian noise added over image: noise is spread throughout

* gaussian noise multiplied then added over image: noise increases with image value

* image folded over and gaussian noise multipled and added to it: peak noise affects mid values, white and black receiving little noise
  in every case i blend in 0.2 and 0.4 of the image

import numpy as np
import cv2
import matplotlib.pyplot as plt

img = cv2.imread(img_path)[...,::-1]/255.0
noise =  np.random.normal(loc=0, scale=1, size=img.shape)

# noise overlaid over image
noisy = np.clip((img + noise*0.2),0,1)
noisy2 = np.clip((img + noise*0.4),0,1)

# noise multiplied by image:
# whites can go to black but blacks cannot go to white
noisy2mul = np.clip((img*(1 + noise*0.2)),0,1)
noisy4mul = np.clip((img*(1 + noise*0.4)),0,1)

noisy2mul = np.clip((img*(1 + noise*0.2)),0,1)
noisy4mul = np.clip((img*(1 + noise*0.4)),0,1)

# noise multiplied by bottom and top half images,
# whites stay white blacks black, noise is added to center
img2 = img*2
n2 = np.clip(np.where(img2 <= 1, (img2*(1 + noise*0.2)), (1-img2+1)*(1 + noise*0.2)*-1 + 2)/2, 0,1)
n4 = np.clip(np.where(img2 <= 1, (img2*(1 + noise*0.4)), (1-img2+1)*(1 + noise*0.4)*-1 + 2)/2, 0,1)


# norm noise for viz only
noise2 = (noise - noise.min())/(noise.max()-noise.min())
plt.figure(figsize=(20,20))
plt.imshow(np.vstack((np.hstack((img, noise2)),
                      np.hstack((noisy, noisy2)),
                      np.hstack((noisy2mul, noisy4mul)),
                      np.hstack((n2, n4)))))
plt.show()
plt.hist(noise.ravel(), bins=100)
plt.show()

img = cv2.imread(img_path)[...,::-1]/255.0 in this line what why [...,-1]/255.0] is used? please explain this !!!

santykish23 · 2022-03-01T05:17:15Z

I have an issue in line 5.. 'str' object has no attribute 'shape' how can i solve this issue?

bro, could you explain this line, img = cv2.imread(img_path)[...,::-1]/255.0 in this line what why [...,-1]/255.0] is used?

xvdp · 2022-03-01T18:39:37Z

Hi, Santykish,

img[...,::-1] simply reverses the channel order from cv2 BGR to RGB, so it can be shown by matplotlib which is RGB
theres many ways that can be done, that one is simply an indexing shortcut. You could use the cv2.cvtColor(img, cv2.COLOR_BGR2RGB) or you could open it with PIL.Image.open(), or you could display it with cv2 and never convert the colors.
/255 - you want a float.

There are a ton of ways in which one can 'add noise', in fact the topic of noise is much greater than what this gist covers.
Do you need to maintain moments of the data? Do you want to denoise a sensor? or generate data from a distribution.

victorhugomarianont · 2022-06-01T01:27:18Z

Having a hard time trying to adapt it to a similar problem. I'm firstly testing this noise function to add later a sepia effect, so this looks more like a vintage image, but did not manage to plot it properly yet. Code goes as follows

def old_photo(file_nm):
    img = cv2.imread("HT.jpg")[...,::-1]/255.0
    noise =  np.random.normal(loc=0, scale=1, size=img.shape)
    
    noised_img = np.clip((img*(1 + noise*0.4)),0,1)
    plt.imshow(noised_img)
       
if __name__ == "__main__":
    print(old_photo("HT.jpg"))

Do you know what can be going wrong here? I'm missing a point I guess

deshwalmahesh · 2022-10-17T09:28:24Z

Having a hard time trying to adapt it to a similar problem. I'm firstly testing this noise function to add later a sepia effect, so this looks more like a vintage image, but did not manage to plot it properly yet. Code goes as follows
def old_photo(file_nm):
    img = cv2.imread("HT.jpg")[...,::-1]/255.0
    noise =  np.random.normal(loc=0, scale=1, size=img.shape)
    
    noised_img = np.clip((img*(1 + noise*0.4)),0,1)
    plt.imshow(noised_img)
       
if __name__ == "__main__":
    print(old_photo("HT.jpg"))
Do you know what can be going wrong here? I'm missing a point I guess

Your old_photo function is returning None. You need to do it in a jupyter notebook. Or you can save the noised_image. How come you're trying to print it? Even if you output the results, it'll be a numpy array.

	import cv2

	def add_gaussian_noise(X_imgs):
	gaussian_noise_imgs = []
	row, col, _ = X_imgs[0].shape
	# Gaussian distribution parameters
	mean = 0
	var = 0.1
	sigma = var ** 0.5

	for X_img in X_imgs:
	gaussian = np.random.random((row, col, 1)).astype(np.float32)
	gaussian = np.concatenate((gaussian, gaussian, gaussian), axis = 2)
	gaussian_img = cv2.addWeighted(X_img, 0.75, 0.25 * gaussian, 0.25, 0)
	gaussian_noise_imgs.append(gaussian_img)
	gaussian_noise_imgs = np.array(gaussian_noise_imgs, dtype = np.float32)
	return gaussian_noise_imgs

	gaussian_noise_imgs = add_gaussian_noise(X_imgs)

Prasad9/add_gaussian_noise.py

liruoteng commented Jan 24, 2019

b-hakim commented Mar 8, 2019 •

edited

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b-hakim commented Mar 8, 2019 •

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xvdp commented May 14, 2019

xvdp commented Jun 2, 2019 •

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PallawiSinghal commented Oct 12, 2019

quantshah commented Jan 28, 2020

RehamMuhammad commented Apr 25, 2020

Guardian99 commented May 29, 2020

xvdp commented Jun 1, 2020 via email

IrshadAhmedHanif commented Mar 20, 2021

rajiv1990 commented Mar 22, 2021

santykish23 commented Mar 1, 2022

santykish23 commented Mar 1, 2022

xvdp commented Mar 1, 2022

victorhugomarianont commented Jun 1, 2022 •

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deshwalmahesh commented Oct 17, 2022

Prasad9/add_gaussian_noise.py

liruoteng commented Jan 24, 2019

b-hakim commented Mar 8, 2019 • edited Loading

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xvdp commented May 14, 2019

xvdp commented Jun 2, 2019 • edited Loading

PallawiSinghal commented Oct 12, 2019

quantshah commented Jan 28, 2020

RehamMuhammad commented Apr 25, 2020

Guardian99 commented May 29, 2020

xvdp commented Jun 1, 2020 via email

IrshadAhmedHanif commented Mar 20, 2021

rajiv1990 commented Mar 22, 2021

santykish23 commented Mar 1, 2022

santykish23 commented Mar 1, 2022

xvdp commented Mar 1, 2022

victorhugomarianont commented Jun 1, 2022 • edited Loading

deshwalmahesh commented Oct 17, 2022

b-hakim commented Mar 8, 2019 •

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xvdp commented Jun 2, 2019 •

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victorhugomarianont commented Jun 1, 2022 •

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