How can I convert this image to grayscale in Python 3.6? - image

I have this code:
bPlane = myImage[:,:,0] - 0.5*(myImage[:,:,2]) - 0.5*(myImage[:,:,1]);
purple = bPlane > 20
purple2 = morphology.remove_small_objects(BW_2, 400);
where myImage is a BGR.
How can I convert "purple2" to a grayscale image in Python 3.6?

If your image is an array (arr) at first, a possible solution would be:
import numpy as np
from PIL import Image
arr = np.random.rand(100,100)
im = Image.fromarray(arr)
gray = im.convert('L') # Converting to grayscale

Related

How to convert numpy array into image using PIL?

The following code gives me black images and I can't understand why:
Imports:
import numpy as np
from PIL import Image
Code:
arr2 = np.zeros((200,200), dtype=int)
arr2[80:120,80:120]=1
im = Image.fromarray(arr2,mode="1")
im.save("C:/Users/Admin/Desktop/testImage.jpg")
I think you want something more like this, using Boolean True and False:
import numpy as np
from PIL import Image
# Create black 1-bit array
arr2 = np.full((200,200), False, dtype=bool)
# Set some bits white
arr2[80:120,80:120]=True
im = Image.fromarray(arr2)
im.save('a.png')
print(im)
<PIL.Image.Image image mode=1 size=200x200 at 0x103FF2770>

Trying to create image from appended array

I have a list of images in a directory. I am trying to extract a column from each image (image size is 403 px by 1288 px by 3 bands) , and sequentially build an array from these columns using numpy append that I want to save as an image. I'm trying to use numpy and pillow to make an image from this appended array.
I have researched Pillor, Numpy documentation
# !/usr/bin/python3
import numpy as np
from numpy import array
from PIL import Image
import os, time, sys, subprocess
savpath =
'C:/data/marsobot/spectral/pushbroom/zwoexperiments/fullsuntheframes/'
os.chdir('C:/data/marsobot/spectral/pushbroom/zwoexperiments/fullsuntheframes/')
toappendarr = np.empty ([403, 1288, 3])
for root, dirs, files in os.walk(".", topdown = False):
for name in files:
img = Image.open(name)
arr = array(img)
value = arr[:, 300, 1]
toappendarr = np.append(toappendarr, value, axis=1)
print(toappendarr.shape)
imgout = Image.fromarray(arr)
imgout.save("output.jpg")
I expected an image but instead I got:
ValueError: all the input arrays must have same number of dimensions

skimage treshold_local does not work with pictures loaded using io.imread

I am was trying out one of the sample Python scripts available from the web site of Scikit Image. This script demonstrates Otsu segmentation at a local level. The script works with pictures loaded using
data.page()
but not using
io.imread
. Any suggestions?
https://scikit-image.org/docs/dev/auto_examples/applications/plot_thresholding.html#sphx-glr-auto-examples-applications-plot-thresholding-py
Picture file
Actual output - the Local thresholding window is empty
As you can see, Global thresholding has worked.But Local Thresholding has failed to produce any results.
Strangely, if I use data.page() then everything works fine.
Script
from skimage import io
from skimage.color import rgb2gray
import matplotlib.pyplot as plt
from skimage.filters import threshold_otsu,threshold_local
import matplotlib
from skimage import data
from skimage.util import img_as_ubyte
filename="C:\\Lenna.png"
mypic= img_as_ubyte (io.imread(filename))
#image = data.page() #This works - why not io.imread ?
imagefromfile=io.imread(filename)
image = rgb2gray(imagefromfile)
global_thresh = threshold_otsu(image)
binary_global = image > global_thresh
block_size = 35
local_thresh = threshold_local(image, block_size, offset=10)
binary_local = image > local_thresh
fig, axes = plt.subplots(nrows=3, figsize=(7, 8))
ax = axes.ravel()
plt.gray()
ax[0].imshow(image)
ax[0].set_title('Original')
ax[1].imshow(binary_global)
ax[1].set_title('Global thresholding')
ax[2].imshow(binary_local)
ax[2].set_title('Local thresholding')
for a in ax:
a.axis('off')
plt.show()
If you load the lenna.png and print its shape you will see it is a 4-channel RGBA image rather than a 3-channel RGB image.
print mypic.shape
(512, 512, 4)
I am not sure which parts of your code apply to which image, so I am not sure where to go next, but I guess you want to just get the RGB part and discard the alpha:
RGB = mypic[...,:3]

pyplot.imsave() saves image correctly but cv2.imwrite() saved the same image as black

from scipy.misc import imread
from matplotlib import pyplot
import cv2
from cv2 import cv
from SRM import SRM ## Module for Statistical Regional Segmentation
im = imread("lena.png")
im2 = cv2.imread("lena.png")
print type(im), type(im2), im.shape, im2.shape
## Prints <type 'numpy.ndarray'> <type 'numpy.ndarray'> (120, 120, 3) (120, 120, 3)
srm = SRM(im, 256)
segmented = srm.run()
srm2 = SRM(im2, 256)
segmented2 = srm2.run()
pic = segmented/256
pic2 = segmented2/256
pyplot.imshow(pic)
pyplot.imsave("onePic.jpg", pic)
pic = pic.astype('uint8')
cv2.imwrite("onePic2.jpg", pic2)
pyplot.show()
onePic.jpg gives the correct segmented image but onePic2.jpg gives a complete black image.
Converting the datatype to uint8 using pic = pic.astype('uint8') did not help. I still gives a black image!
onePic.jpg using pyplot.imsave():
onePic2.jpg using cv2.imwrite():
Please help!
Before converting pic to uint8, you need to multiply it by 255 to get the correct range.
Although I agree with #sansuiso, in my case I found a possible edge case where my images were being shifted either one bit up in the scale or one bit down.
Since we're dealing with unsigned ints, a single shift means a possible underflow/overflow, and this can corrupt the whole image.
I found cv2's convertScaleAbs with an alpha value of 255.0 to yield better results.
def write_image(path, img):
# img = img*(2**16-1)
# img = img.astype(np.uint16)
# img = img.astype(np.uint8)
img = cv.convertScaleAbs(img, alpha=(255.0))
cv.imwrite(path, img)
This answer goes into more detail.
I encountered a similar situation with face detection, I wonder if there is a better way to execute this, here is my solution here as a reference.
from deepface import DeepFace
import cv2
import matplotlib.pyplot as plt
# import image and output
img_path = "image.jpg"
detected_face = DeepFace.detectFace(img_path, target_size = (128, 128))
plt.imshow(detected_face)
# image color scaling and saving
detected_face = cv2.cvtColor( detected_face,cv2.COLOR_BGR2RGB)
detected_face = cv2.convertScaleAbs(detected_face, alpha=(255.0))
cv2.imwrite("image_thumbnail.jpg", detected_face)

Is it possible to have black and white and color image on same window by using opencv?

Is it possible to have black-and-white and color image on same window by using opencv libraray? How can I have both of these images on same window?
fraxel's answer has solved the problem with old cv interface. I would like to show it using cv2 interface, just to understand how this easy in new cv2 module. (May be it would be helpful for future visitors). Below is the code:
import cv2
import numpy as np
im = cv2.imread('kick.jpg')
img = cv2.imread('kick.jpg',0)
# Convert grayscale image to 3-channel image,so that they can be stacked together
imgc = cv2.cvtColor(img,cv2.COLOR_GRAY2BGR)
both = np.hstack((im,imgc))
cv2.imshow('imgc',both)
cv2.waitKey(0)
cv2.destroyAllWindows()
And below is the output I got:
Yes it is, here is an example, expaination in the comments:
import cv
#open color and b/w images
im = cv.LoadImageM('1_tree_small.jpg')
im2 = cv.LoadImageM('1_tree_small.jpg',cv.CV_LOAD_IMAGE_GRAYSCALE)
#set up our output and b/w in rgb space arrays:
bw = cv.CreateImage((im.width,im.height), cv.IPL_DEPTH_8U, 3)
new = cv.CreateImage((im.width*2,im.height), cv.IPL_DEPTH_8U, 3)
#create a b/w image in rgb space
cv.Merge(im2, im2, im2, None, bw)
#set up and add the color image to the left half of our output image
cv.SetImageROI(new, (0,0,im.width,im.height))
cv.Add(new, im, new)
#set up and add the b/w image to the right half of output image
cv.SetImageROI(new, (im.width,0,im.width,im.height))
cv.Add(new, bw, new)
cv.ResetImageROI(new)
cv.ShowImage('double', new)
cv.SaveImage('double.jpg', new)
cv.WaitKey(0)
Its in python, but easy to convert to whatever..
Small improvement to the code with modern writing
concatenate
instead of
hstack
that is discontinued (stack can also be used)
import cv2
import numpy as np
im = cv2.imread('kick.jpg')
img = cv2.imread('kick.jpg',0)
# Convert grayscale image to 3-channel image,so that they can be stacked together
imgc = cv2.cvtColor(img,cv2.COLOR_GRAY2BGR)
both = np.concatenate((im,imgc), axis=1) #1 : horz, 0 : Vert.
cv2.imshow('imgc',both)
cv2.waitKey(0)
cv2.destroyAllWindows()
import cv2
img = cv2.imread("image.jpg" , cv2.IMREAD_GRAYSCALE)
cv2.imshow("my image",img)
cv2.waitkey(0)
cv2.destroyAllWindow
#The image file should be in the application folder.
#The output file will be 'my image' name.
#The bottom line is to free up memory.

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