3

I am using opencv in python to rotate an image and the original and the resulted images are differrent is somethings, I am doing my transformation through this part of code:

img = cv2.imread("image.tif")    
new_image = cv2.getRotationMatrix2D((cols / 2, rows / 2), correction_angle, 1)
dst = cv2.warpAffine(img, new_image , (cols, rows))
cv2.imwrite("Rotated_image.tif", dst)
  • The original image's size is 1.7 Mb, The image's resolution is 300 dpi, and the color space is YCbCr.
  • The issue is that the resulting image with 12.5 Mb size, 96 dpi, the color space is RGB, and with compression "LZW"!

My question is that: Can I keep the main properties of the original image? and why rotating an image changes the size this way?

Note: The bit depth is 24 in both images.

Neweshy
  • 31
  • 4

1 Answers1

0

Calling cv2.imread with only the name of the file uses the default value cv.IMREAD_COLOR for the second parameter, about which the documentation says:

If set, always convert image to the 3 channel BGR color image.

So, your image is always converted to RGB. You can try using cv.IMREAD_ANYCOLOR for the second parameter of imread, but I don't think you can use cv2.warpAffine on it trivially then.

The difference in the stored DPI information stems from the fact that you write the new image without any meta data. imwrite allows you to specify parameters (see here), but, unfortunately, they are not very well documented. I am not sure if this kind of data can be written out of the box with OpenCV.

Andreas Unterweger
  • 585
  • 4
  • 16