Letters blurry / fuzzy after crop function

问题

after attempting to crop my image in several locations by saving the list of coordinates to an array the letters in the cropped area become extremely blurry and I cannot figure out why.

The original image looks like

After cropping the image looks like

The code in questions is as follows:

import numpy as np
import cv2

im2 = cv2.imread('1.jpg')
im = im2.copy()

gray = cv2.cvtColor(im,cv2.COLOR_BGR2GRAY)
blur = cv2.GaussianBlur(gray,(5,5),0)
thresh = cv2.adaptiveThreshold(blur,255,1,1,11,2)


contours,hierarchy = cv2.findContours(thresh,cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)


squares = []

for cnt in contours:
    if cv2.contourArea(cnt)>50:
        [x,y,w,h] = cv2.boundingRect(cnt)

        if  h>28 and h<34:
            rect = (cv2.rectangle(im,(x,y),(x+w,y+h),(255,255,255),3))
            squares.append(cv2.boundingRect(cnt))
            cv2.imwrite('norm1.jpg',im)

crop_img = [[[255, 255, 255] for x in xrange(377)] for x in xrange(377) ]

for s in squares:
    x = s[0]
    y = s[1]
    w = s[2]
    h = s[3]
    img = im[y:y+h,x:x+w]
    for col in range(y,y+h):
        for row in range(x,x+w):
            if img[col - y][row - x].tolist() == [0,0,0]:
                crop_img[col][row] = [0,0,0]
cv2.imwrite("cropped.jpg", np.array(crop_img))

Any help would be greatly appreciated!

回答1:

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

im2 = cv2.imread('norm1_zps89266edb.jpg')
im = im2.copy()

gray = cv2.cvtColor(im,cv2.COLOR_BGR2GRAY)
blur = cv2.GaussianBlur(gray,(5,5),0)
ret3,thresh = cv2.threshold(blur,0,255,cv2.THRESH_BINARY+cv2.THRESH_OTSU)

#we ony want the external contours
contours,hierarchy = cv2.findContours(thresh.copy(),cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE) 
#extract the countours with area > 50
squares = [cnt for cnt in contours if cv2.contourArea(cnt) > 50]

#mask array with the same shape as img (but only 1 channel)
mask = np.zeros((im.shape[0], im.shape[1]))
#draw the contours filled with 255 values. 
cv2.drawContours(mask,squares,-1,255,-1)

newImage = np.where(mask==255, thresh, 255)

plt.imshow(newImage)
plt.show()

cv2.imwrite("cropped.jpg", newImage)

output:

来源：https://stackoverflow.com/questions/21153466/letters-blurry-fuzzy-after-crop-function

标签

python

OpenCV

crop