When applying levels to greyscale image nothing happens

[dma_k]

While playing with this image I have found out the following strange behaviour:

• Convert the image to grayscale 265.
• Call Image → Adjust → Levels. Enable "Show preview" and "Apply to image".
• Set "Black point" to value 192.

Result: The preview shows the image as expected. But for the original image the operation is applied with no visible changes.

The reason is that preview applies leves to smaller (resized) image. I think that preview is confusing the user as it does not reflect the reality.

[xnview]

Yes, preview is not always good...