I want to compare two images to check if they are equal or not, but for that i need to compare a specific region (ROI) of both images.
I've cropped the areas i want to compare, but now i would like to know how can i do that process, because i can't directly compare the cropped images.
How can i for example get the average pixels values of both cropped images and compare them?
Update: I've solved the situation.
Current code:
import cv2
import numpy as np
from skimage.measure import compare_ssim as ssim
def mse(imageA, imageB):
# the 'Mean Squared Error' between the two images is the sum of the squared difference between the two images;
err = np.sum((imageA.astype("float") - imageB.astype("float")) ** 2)
err /= float(imageA.shape[0] * imageA.shape[1])
polarity_ok = cv2.resize(cv2.imread("polarity_OK_edited.jpg"),None,fx=0.2, fy=0.2) #resize the image to be smaller
polarity_nok = cv2.resize(cv2.imread("Polarity_NOK1.JPG"), None,fx=0.2, fy=0.2) #resize the image to be smaller
polarity_ok_cropped = polarity_ok[350:408, 97:111]
polarity_nok_cropped = polarity_nok[350:408, 97:111]
polarity_ok_cropped1 = polarity_ok[359:409, 232:240]
polarity_nok_cropped1 = polarity_nok[359:409, 232:240]
polarity_ok_cropped2 = polarity_ok[118:153, 44:69]
polarity_nok_cropped2 = polarity_nok[118:153, 44:69]
polarity_ok_cropped3 = polarity_ok[94:142, 192:197]
polarity_nok_cropped3 = polarity_nok[94:142, 192:197]
m = mse(polarity_ok_cropped, polarity_nok_cropped)
s = ssim(polarity_ok_cropped, polarity_nok_cropped, multichannel=True)
diff = cv2.subtract(polarity_ok_cropped, polarity_nok_cropped)
result = not np.any(diff)
m1 = mse(polarity_ok_cropped1, polarity_nok_cropped1)
s1 = ssim(polarity_ok_cropped1, polarity_nok_cropped1, multichannel=True)
diff1 = cv2.subtract(polarity_ok_cropped1, polarity_nok_cropped1)
result1 = not np.any(diff1)
m2 = mse(polarity_ok_cropped2, polarity_nok_cropped2)
s2 = ssim(polarity_ok_cropped2, polarity_nok_cropped2, multichannel=True)
diff2 = cv2.subtract(polarity_ok_cropped2, polarity_nok_cropped2)
result2 = not np.any(diff2)
m3 = mse(polarity_ok_cropped2, polarity_nok_cropped2)
s3 = ssim(polarity_ok_cropped2, polarity_nok_cropped2, multichannel=True)
diff3 = cv2.subtract(polarity_ok_cropped3, polarity_nok_cropped3)
result3 = not np.any(diff3)
if (result and result1 and result2 and result3):
print ("The polarity is correct. Awesome :)")
else:
print ("Nice try, but the polarity is incorrect. Take another chance!")
If you know exactly where the objects you want to compare are, simple and fast method using OpenCV to compare two images is to extract histograms using calcHistogram() for each channel (RGB or HSV) and then compare them using compareHist().
Further infos and examples might be found here: Histogram comparsion.
You can use the Structural Similarity Index (SSIM) as giving the 2 images as input and returning a score value in the range [-1, 1]. A score of 1 indicating a perfect similarity between 2 input images (In case of both images are equal)
from skimage.measure import compare_ssim
(score, diff) = compare_ssim(image1, image2, full=True)
Btw Converting the input images before comparison into grayscale is prefered.
One more way to do the same :
from PIL import Image
import math, operator
i1 = Image.open('./image1.png')
i2 = Image.open('./image2.png')
#this will resize any format of image file
assert i1.mode == i2.mode, "Different kinds of images."
assert i1.size == i2.size, "Different sizes."
pairs = zip(i1.getdata(), i2.getdata())
if len(i1.getbands()) == 1:
# for gray-scale jpegs
dif = sum(abs(p1-p2) for p1,p2 in pairs)
else:
dif = sum(abs(c1-c2) for p1,p2 in pairs for c1,c2 in zip(p1,p2))
ncomponents = i1.size[0] * i1.size[1] * 3
print ("Difference (percentage):", (dif / 255.0 * 100) / ncomponents)
You need to install pillow.
hope this will help you.
I'm trying to interpolate between two images in Python.
Images are of shapes (188, 188)
I wish to interpolate the image 'in-between' these two images. Say Image_1 is at location z=0 and Image_2 is at location z=2. I want the interpolated image at location z=1.
I believe this answer (MATLAB) contains a similar problem and solution.
Creating intermediate slices in a 3D MRI volume with MATLAB
I've tried to convert this code to Python as follows:
from scipy.interpolate import interpn
from scipy.interpolate import griddata
# Construct 3D volume from images
# arr.shape = (2, 182, 182)
arr = np.r_['0,3', image_1, image_2]
slices,rows,cols = arr.shape
# Construct meshgrids
[X,Y,Z] = np.meshgrid(np.arange(cols), np.arange(rows), np.arange(slices));
[X2,Y2,Z2] = np.meshgrid(np.arange(cols), np.arange(rows), np.arange(slices*2));
# Run n-dim interpolation
Vi = interpn([X,Y,Z], arr, np.array([X1,Y1,Z1]).T)
However, this produces an error:
ValueError: The points in dimension 0 must be strictly ascending
I suspect I am not constructing my meshgrid(s) properly but am kind of lost on whether or not this approach is correct.
Any ideas?
---------- Edit -----------
Found some MATLAB code that appears to solve this problem:
Interpolating Between Two Planes in 3d space
I attempted to convert this to Python:
from scipy.ndimage.morphology import distance_transform_edt
from scipy.interpolate import interpn
def ndgrid(*args,**kwargs):
"""
Same as calling ``meshgrid`` with *indexing* = ``'ij'`` (see
``meshgrid`` for documentation).
"""
kwargs['indexing'] = 'ij'
return np.meshgrid(*args,**kwargs)
def bwperim(bw, n=4):
"""
perim = bwperim(bw, n=4)
Find the perimeter of objects in binary images.
A pixel is part of an object perimeter if its value is one and there
is at least one zero-valued pixel in its neighborhood.
By default the neighborhood of a pixel is 4 nearest pixels, but
if `n` is set to 8 the 8 nearest pixels will be considered.
Parameters
----------
bw : A black-and-white image
n : Connectivity. Must be 4 or 8 (default: 8)
Returns
-------
perim : A boolean image
From Mahotas: http://nullege.com/codes/search/mahotas.bwperim
"""
if n not in (4,8):
raise ValueError('mahotas.bwperim: n must be 4 or 8')
rows,cols = bw.shape
# Translate image by one pixel in all directions
north = np.zeros((rows,cols))
south = np.zeros((rows,cols))
west = np.zeros((rows,cols))
east = np.zeros((rows,cols))
north[:-1,:] = bw[1:,:]
south[1:,:] = bw[:-1,:]
west[:,:-1] = bw[:,1:]
east[:,1:] = bw[:,:-1]
idx = (north == bw) & \
(south == bw) & \
(west == bw) & \
(east == bw)
if n == 8:
north_east = np.zeros((rows, cols))
north_west = np.zeros((rows, cols))
south_east = np.zeros((rows, cols))
south_west = np.zeros((rows, cols))
north_east[:-1, 1:] = bw[1:, :-1]
north_west[:-1, :-1] = bw[1:, 1:]
south_east[1:, 1:] = bw[:-1, :-1]
south_west[1:, :-1] = bw[:-1, 1:]
idx &= (north_east == bw) & \
(south_east == bw) & \
(south_west == bw) & \
(north_west == bw)
return ~idx * bw
def signed_bwdist(im):
'''
Find perim and return masked image (signed/reversed)
'''
im = -bwdist(bwperim(im))*np.logical_not(im) + bwdist(bwperim(im))*im
return im
def bwdist(im):
'''
Find distance map of image
'''
dist_im = distance_transform_edt(1-im)
return dist_im
def interp_shape(top, bottom, num):
if num<0 and round(num) == num:
print("Error: number of slices to be interpolated must be integer>0")
top = signed_bwdist(top)
bottom = signed_bwdist(bottom)
r, c = top.shape
t = num+2
print("Rows - Cols - Slices")
print(r, c, t)
print("")
# rejoin top, bottom into a single array of shape (2, r, c)
# MATLAB: cat(3,bottom,top)
top_and_bottom = np.r_['0,3', top, bottom]
#top_and_bottom = np.rollaxis(top_and_bottom, 0, 3)
# create ndgrids
x,y,z = np.mgrid[0:r, 0:c, 0:t-1] # existing data
x1,y1,z1 = np.mgrid[0:r, 0:c, 0:t] # including new slice
print("Shape x y z:", x.shape, y.shape, z.shape)
print("Shape x1 y1 z1:", x1.shape, y1.shape, z1.shape)
print(top_and_bottom.shape, len(x), len(y), len(z))
# Do interpolation
out = interpn((x,y,z), top_and_bottom, (x1,y1,z1))
# MATLAB: out = out(:,:,2:end-1)>=0;
array_lim = out[-1]-1
out[out[:,:,2:out] >= 0] = 1
return out
I call this as follows:
new_image = interp_shape(image_1,image_2, 1)
Im pretty sure this is 80% of the way there but I still get this error when running:
ValueError: The points in dimension 0 must be strictly ascending
Again, I am probably not constructing my meshes correctly. I believe np.mgrid should produce the same result as MATLABs ndgrid though.
Is there a better way to construct the ndgrid equivalents?
I figured this out. Or at least a method that produces desirable results.
Based on: Interpolating Between Two Planes in 3d space
def signed_bwdist(im):
'''
Find perim and return masked image (signed/reversed)
'''
im = -bwdist(bwperim(im))*np.logical_not(im) + bwdist(bwperim(im))*im
return im
def bwdist(im):
'''
Find distance map of image
'''
dist_im = distance_transform_edt(1-im)
return dist_im
def interp_shape(top, bottom, precision):
'''
Interpolate between two contours
Input: top
[X,Y] - Image of top contour (mask)
bottom
[X,Y] - Image of bottom contour (mask)
precision
float - % between the images to interpolate
Ex: num=0.5 - Interpolate the middle image between top and bottom image
Output: out
[X,Y] - Interpolated image at num (%) between top and bottom
'''
if precision>2:
print("Error: Precision must be between 0 and 1 (float)")
top = signed_bwdist(top)
bottom = signed_bwdist(bottom)
# row,cols definition
r, c = top.shape
# Reverse % indexing
precision = 1+precision
# rejoin top, bottom into a single array of shape (2, r, c)
top_and_bottom = np.stack((top, bottom))
# create ndgrids
points = (np.r_[0, 2], np.arange(r), np.arange(c))
xi = np.rollaxis(np.mgrid[:r, :c], 0, 3).reshape((r**2, 2))
xi = np.c_[np.full((r**2),precision), xi]
# Interpolate for new plane
out = interpn(points, top_and_bottom, xi)
out = out.reshape((r, c))
# Threshold distmap to values above 0
out = out > 0
return out
# Run interpolation
out = interp_shape(image_1,image_2, 0.5)
Example output:
I came across a similar problem where I needed to interpolate the shift between frames where the change did not merely constitute a translation but also changes to the shape itself . I solved this problem by :
Using center_of_mass from scipy.ndimage.measurements to calculate the center of the object we want to move in each frame
Defining a continuous parameter t where t=0 first and t=1 last frame
Interpolate the motion between two nearest frames (with regard to a specific t value) by shifting the image back/forward via shift from scipy.ndimage.interpolation and overlaying them.
Here is the code:
def inter(images,t):
#input:
# images: list of arrays/frames ordered according to motion
# t: parameter ranging from 0 to 1 corresponding to first and last frame
#returns: interpolated image
#direction of movement, assumed to be approx. linear
a=np.array(center_of_mass(images[0]))
b=np.array(center_of_mass(images[-1]))
#find index of two nearest frames
arr=np.array([center_of_mass(images[i]) for i in range(len(images))])
v=a+t*(b-a) #convert t into vector
idx1 = (np.linalg.norm((arr - v),axis=1)).argmin()
arr[idx1]=np.array([0,0]) #this is sloppy, should be changed if relevant values are near [0,0]
idx2 = (np.linalg.norm((arr - v),axis=1)).argmin()
if idx1>idx2:
b=np.array(center_of_mass(images[idx1])) #center of mass of nearest contour
a=np.array(center_of_mass(images[idx2])) #center of mass of second nearest contour
tstar=np.linalg.norm(v-a)/np.linalg.norm(b-a) #define parameter ranging from 0 to 1 for interpolation between two nearest frames
im1_shift=shift(images[idx2],(b-a)*tstar) #shift frame 1
im2_shift=shift(images[idx1],-(b-a)*(1-tstar)) #shift frame 2
return im1_shift+im2_shift #return average
if idx1<idx2:
b=np.array(center_of_mass(images[idx2]))
a=np.array(center_of_mass(images[idx1]))
tstar=np.linalg.norm(v-a)/np.linalg.norm(b-a)
im1_shift=shift(images[idx2],-(b-a)*(1-tstar))
im2_shift=shift(images[idx1],(b-a)*(tstar))
return im1_shift+im2_shift
Result example
I don't know the solution to your problem, but I don't think it's possible to do this with interpn.
I corrected the code that you tried, and used the following input images:
But the result is:
Here's the corrected code:
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.cm as cm
from scipy import interpolate
n = 8
img1 = np.zeros((n, n))
img2 = np.zeros((n, n))
img1[2:4, 2:4] = 1
img2[4:6, 4:6] = 1
plt.figure()
plt.imshow(img1, cmap=cm.Greys)
plt.figure()
plt.imshow(img2, cmap=cm.Greys)
points = (np.r_[0, 2], np.arange(n), np.arange(n))
values = np.stack((img1, img2))
xi = np.rollaxis(np.mgrid[:n, :n], 0, 3).reshape((n**2, 2))
xi = np.c_[np.ones(n**2), xi]
values_x = interpolate.interpn(points, values, xi, method='linear')
values_x = values_x.reshape((n, n))
print(values_x)
plt.figure()
plt.imshow(values_x, cmap=cm.Greys)
plt.clim((0, 1))
plt.show()
I think the main difference between your code and mine is in the specification of xi. interpn tends to be somewhat confusing to use, and I've explained it in greater detail in an older answer. If you're curious about the mechanics of how I've specified xi, see this answer of mine explaining what I've done.
This result is not entirely surprising, because interpn just linearly interpolated between the two images: so the parts which had 1 in one image and 0 in the other simply became 0.5.
Over here, since one image is the translation of the other, it's clear that we want an image that's translated "in-between". But how would interpn interpolate two general images? If you had one small circle and one big circle, is it in any way clear that there should be a circle of intermediate size "between" them? What about interpolating between a dog and a cat? Or a dog and a building?
I think you are essentially trying to "draw lines" connecting the edges of the two images and then trying to figure out the image in between. This is similar to sampling a moving video at a half-frame. You might want to check out something like optical flow, which connects adjacent frames using vectors. I'm not aware if and what python packages/implementations are available though.
What technique do you recommend to segment the characters in this image to be ready to fed a model like the ones use with MNIST dataset; because they take one character at a time. This question is regadless the importance of transforming the image and the binarization of it.
Thanks!
As a starting point i would try the following:
Use OTSU threshold.
Than do some morphological operations to get rid of noise and to isolate each digit.
Run connected component labling.
Fed each connected component to your classifier to get recognize the digit if the classification score is low discard.
Final validation you expect all the digit to be more or less on line and in more or less some constant distance from each other.
Here are the first 4 stages. Now you need to add your recognition software to recognize the digits.
import cv2
import numpy as np
from matplotlib import pyplot as plt
# Params
EPSSILON = 0.4
MIN_AREA = 10
BIG_AREA = 75
# Read img
img = cv2.imread('i.jpg',0)
# Otzu threshold
a,thI = cv2.threshold(img,0,255,cv2.THRESH_BINARY_INV+cv2.THRESH_OTSU)
# Morpholgical
se = cv2.getStructuringElement(cv2.MORPH_ELLIPSE,(1,1))
thIMor = cv2.morphologyEx(thI,cv2.MORPH_CLOSE,se)
# Connected compoent labling
stats = cv2.connectedComponentsWithStats(thIMor,connectivity=8)
num_labels = stats[0]
labels = stats[1]
labelStats = stats[2]
# We expect the conneccted compoennt of the numbers to be more or less with a constats ratio
# So we find the medina ratio of all the comeonets because the majorty of connected compoent are numbers
ratios = []
for label in range(num_labels):
connectedCompoentWidth = labelStats[label,cv2.CC_STAT_WIDTH]
connectedCompoentHeight = labelStats[label, cv2.CC_STAT_HEIGHT]
ratios.append(float(connectedCompoentWidth)/float(connectedCompoentHeight))
# Find median ratio
medianRatio = np.median(np.asarray(ratios))
# Go over all the connected component again and filter out compoennt that are far from the ratio
filterdI = np.zeros_like(thIMor)
filterdI[labels!=0] = 255
for label in range(num_labels):
# Ignore biggest label
if(label==1):
filterdI[labels == label] = 0
continue
connectedCompoentWidth = labelStats[label,cv2.CC_STAT_WIDTH]
connectedCompoentHeight = labelStats[label, cv2.CC_STAT_HEIGHT]
ratio = float(connectedCompoentWidth)/float(connectedCompoentHeight)
if ratio > medianRatio + EPSSILON or ratio < medianRatio - EPSSILON:
filterdI[labels==label] = 0
# Filter small or large compoennt
if labelStats[label,cv2.CC_STAT_AREA] < MIN_AREA or labelStats[label,cv2.CC_STAT_AREA] > BIG_AREA:
filterdI[labels == label] = 0
plt.imshow(filterdI)
# Now go over each of the left compoenet and run the number recognotion
stats = cv2.connectedComponentsWithStats(filterdI,connectivity=8)
num_labels = stats[0]
labels = stats[1]
labelStats = stats[2]
for label in range(num_labels):
# Crop the bounding box around the component
left = labelStats[label,cv2.CC_STAT_LEFT]
top = labelStats[label, cv2.CC_STAT_TOP]
width = labelStats[label, cv2.CC_STAT_WIDTH]
height = labelStats[label, cv2.CC_STAT_HEIGHT]
candidateDigit = labels[top:top+height,left:left+width]
# plt.figure(label)
# plt.imshow(candidateDigit)
I connect to the Amitay answer.
For the 2:
I would use thinning as morphological operation (look thinning algorithm in opencv)
For the 3:
And in OpenCV 3.0 there is already a function called cv::connectedComponents)
Hope it helps
This is a program for face recognition using pca logic. Everything went fine except for the index error that came up at the end of the program.
When I run the code I get an index error at the fourth last line of my program.
distances.append((dist, y[i]))
IndexError: list index out of range
can anyone just help in this. I am newbie into python, so am I not so expert in solving.
Here is my code :
from sklearn.decomposition import RandomizedPCA
import numpy as np
import glob
import cv2
import math
import os.path
import string
#function to get ID from filename
def ID_from_filename(filename):
part = string.split(filename, '/')
return part[1].replace("s", "")
#function to convert image to right format
def prepare_image(filename):
img_color = cv2.imread(filename)
img_gray = cv2.cvtColor(img_color, cv2.cv.CV_RGB2GRAY)
img_gray = cv2.equalizeHist(img_gray)
return img_gray.flat
IMG_RES = 92 * 112 # img resolution
NUM_EIGENFACES = 10 # images per train person
NUM_TRAINIMAGES = 110 # total images in training set
#loading training set from folder train_faces
folders = glob.glob('train_faces/*')
# Create an array with flattened images X
# and an array with ID of the people on each image y
X = np.zeros([NUM_TRAINIMAGES, IMG_RES], dtype='int8')
y = []
# Populate training array with flattened imags from subfolders of
train_faces and names
c = 0
for x, folder in enumerate(folders):
train_faces = glob.glob(folder + '/*')
for i, face in enumerate(train_faces):
X[c,:] = prepare_image(face)
y.append(ID_from_filename(face))
c = c + 1
# perform principal component analysis on the images
pca = RandomizedPCA(n_components=NUM_EIGENFACES, whiten=True).fit(X)
X_pca = pca.transform(X)
# load test faces (usually one), located in folder test_faces
test_faces = glob.glob('test_faces/*')
# Create an array with flattened images X
X = np.zeros([len(test_faces), IMG_RES], dtype='int8')
# Populate test array with flattened imags from subfolders of train_faces
for i, face in enumerate(test_faces):
X[i,:] = prepare_image(face)
# run through test images (usually one)
for j, ref_pca in enumerate(pca.transform(X)):
distances = []
# Calculate euclidian distance from test image to each of the known
images and save distances
for i, test_pca in enumerate(X_pca):
dist = math.sqrt(sum([diff**2 for diff in (ref_pca - test_pca)]))
distances.append((dist, y[i]))
found_ID = min(distances)[1]
print "Identified (result: "+ str(found_ID) +" - dist - " +
str(min(distances)[0]) + ")"
Your i in the loop below goes up to the length of X_pca - 1
for i, test_pca in enumerate(X_pca):
dist = math.sqrt(sum([diff**2 for diff in (ref_pca - test_pca)]))
distances.append((dist, y[i]))
However, your y is not built to have that length necessarily:
for x, folder in enumerate(folders):
train_faces = glob.glob(folder + '/*')
for i, face in enumerate(train_faces):
X[c,:] = prepare_image(face)
y.append(ID_from_filename(face))
So you are using an index i which is greater than the bounds of your list y.