RawTherapee tiff compression?

Software RawTherapee
1

If I save my RAW file in .tiff format “compression” mode, is this lossless comperssion or not?

2

It’s lossless.

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3

From the test that I carried out it does not seem lossless at least at 16 bit

4

What test? Please provide some evidence of this.

That would indicate a very severe bug if it is indeed the case.

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5

Sorry, I could not reproduce it today with 5.8, maybe there was a problem with my profile.
The test that I usually carry out uses a under exposed image:

I export the image as it is at 16 bit with compression or not.

I perform an exposure compensation (e.g. 9) on the derivative files. I do a visual check (yesterday it was visible) and then a programmatic test using this Python script that uses PIL external library:

from PIL import Image, ImageChops
img1 = Image.open("_DSC0315noncomp.tif")
img2 = Image.open("_DSC0315comp.tif")
diff = ImageChops.difference(img1, img2)
# findig extrema in this case diff should be zero. 
if diff.getextrema() != ((0, 0), (0, 0), (0, 0)):
    print("Different images")
# showing the difference
diff.show()

Sorry for this false alarm, I’ll let you know if it happens again.

6

Pillow does not work w/ 16-bit RGB files of any kind, it converts internally to 8-bits (i.e. throws away LSBs). It only supports 16-bit grayscale.

Try e.g. w/ OpenCV’s cv2.imread instead.

1 Like
7

Or tifffile

8

Or ImageMagick’s compare.

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