If I have an image like below, how can I add border all around the image such that the overall height and width of the final image increases but the height and width of the original image stays as-is in the middle.
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6How about cv2.copyMakeBorder ?Dan Mašek– Dan Mašek2016-03-28 03:49:00 +00:00Commented Mar 28, 2016 at 3:49
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1By the way, opencv official documentation provides a tutorial how to append a border to am image using cv2.copyMakeBorder.Evgeny Bobkin– Evgeny Bobkin2019-06-05 09:58:14 +00:00Commented Jun 5, 2019 at 9:58
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4 Answers
The following code adds a constant border of size 10 pixels to all four sides of your original image.
For the colour, I have assumed that you want to use the average gray value of the background, which I have calculated from the mean value of bottom two lines of your image. Sorry, somewhat hard coded, but shows the general how-to and can be adapted to your needs.
If you leave border_size values for bottom and right at 0, you even get a symmetric border.
Other values for BORDER_TYPE are possible, such as BORDER_DEFAULT, BORDER_REPLICATE, BORDER_WRAP.
For more details cf: http://docs.opencv.org/trunk/d3/df2/tutorial_py_basic_ops.html#gsc.tab=0
import numpy as np
import cv2
im = cv2.imread('image.jpg')
row, col = im.shape[:2]
bottom = im[row-2:row, 0:col]
mean = cv2.mean(bottom)[0]
border_size = 10
border = cv2.copyMakeBorder(
im,
top=border_size,
bottom=border_size,
left=border_size,
right=border_size,
borderType=cv2.BORDER_CONSTANT,
value=[mean, mean, mean]
)
cv2.imshow('image', im)
cv2.imshow('bottom', bottom)
cv2.imshow('border', border)
cv2.waitKey(0)
cv2.destroyAllWindows()
1 Comment
hum3
Using the tutorial I thought that the value for Red (confusingly labelled Blue) should be [255, 0, 0]. But actually it was [1.0, 0, 0] with floats as the image value colours.
Answer in one line
outputImage = cv2.copyMakeBorder(
inputImage,
topBorderWidth,
bottomBorderWidth,
leftBorderWidth,
rightBorderWidth,
cv2.BORDER_CONSTANT,
value=color of border
)
Comments
Try This:
import cv2
import numpy as np
img=cv2.imread("img_src.jpg")
h,w=img.shape[0:2]
base_size=h+20,w+20,3
# make a 3 channel image for base which is slightly larger than target img
base=np.zeros(base_size,dtype=np.uint8)
cv2.rectangle(base,(0,0),(w+20,h+20),(255,255,255),30) # really thick white rectangle
base[10:h+10,10:w+10]=img # this works
Comments
Add border using openCV
import cv2
white = [255,255,255]
img1 = cv2.imread('input.png')
constant= cv2.copyMakeBorder(img1,20,20,20,20,cv2.BORDER_CONSTANT,value=white)
cv2.imwrite('output.png',constant)
