Python: Read and write TIFF 16 bit , three channel , colour images

Question

Does anyone have a method for importing a 16 bit per channel, 3 channel TIFF image in Python?

I have yet to find a method which will preserve the 16 bit depth per ch

Answer 1

The answer by @Jaime works.

In the mean time I managed to also solve the problem using cv2.imread in OpenCV.

By default cv2.imread will convert a 16 bit, three channel image in a.tif to 8 bit as shown in the question.

cv2.imread accepts a flag after the filename ( cv2.imread(filename[, flags]) ) which specifies the colour type of the loaded image cf. the documentation:

1. >0 returns a 3 channel colour image. This results in conversion to 8 bit as shown above.
2. 0 returns a greyscale image. Also results in conversion to 8 bit.
3. <0 returns the image as is. This will return a 16 bit image.

So the following will read the image without conversion:

>>> im = cv2.imread('a.tif', -1)
>>> im.dtype
dtype('uint16')
>>> im.shape
(288, 384, 3)

Note that OpenCV returns the R, G and B channels in reverse order so im[:,:,0] is the B channel, im[:,:,1] the G channel and im[:,:,2] is the R channel.

I have also found that cv2.imwrite can write 16 bit, three channel TIFF files.

>>> cv2.imwrite('out.tif', im)

Checking the bit depth with ImageMagick:

$ identify -verbose out.tif
  Format: TIFF (Tagged Image File Format)
  Class: DirectClass
  Geometry: 384x288+0+0
  Resolution: 72x72
  Print size: 5.33333x4
  Units: PixelsPerInch
  Type: TrueColor
  Base type: TrueColor
  Endianess: MSB
  Colorspace: sRGB
  Depth: 16-bit
  Channel depth:
    red: 16-bit
    green: 16-bit
    blue: 16-bit
  ....