David Burren <[EMAIL PROTECTED]> writes:

> Adjusting the white point will scale all the colours in the image.
> For example if you had green writing on yellow paper, adjusting the
> white point like this would change the green to cyan (and red to
> magenta, but not affect any blue writing).
> Mind you, for Steve's receipts and his use of them, the final result
> in B&W might be OK.
> Adjusting the white point is a very useful technique for colours
> _within_ an image, but it's a bit flawed as a general method for
> rendering the surrounding paper as white (unless the ink is pure
> black).

Right, unless the ink is pure black, which is very common for scanned
documents. With a scanned document, what you usually want to achieve
is to have black text on white background. Unless the scan is
perfectly adjusted, you usually have dark gray text on light gray
background. Picking the white and black points fixes this very
conveniently. If there are photos on the same page, the photo should
be handled separately from the text anyway. It's best put on a
separate layer and treated independently from the text.

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