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Access to the window
The window controlling the resampling can be
opened with the menu « Image  Resampling ».
You need to select beforehand the image to
resample in the stack. In the window, you need
to specify the reference image, whether you
wish to keep or not the “full” pixels, or just the
“grey levels” code on 8 bits (quicker), choose
the estimation method for the pixel values and
at the end, say whether the original image
needs to be replaced by the newly sampled
image, or kept in the stack.
Attention: Please note that the resampling methods in Aladin do no preserve the flux,
i.e. the sum of the pixel values before the resampling is not the same as the one
afterwards.
Note: An image that was resampled shows the following logo in the view:
Trick: Using the translucence of images (cf. ) is a quicker and more flexible alternative
to resampling. It is however less precise since it does not act pixel-by-pixel, but only
based on the four corners and does a global approximation for the other pixels location.
5.12Arithmetic operations on images
Menu: Image  Arithmetic operations …
Image  Convolution
Image  Pixel normalisation [0..1]
Addition, subtraction, multiplication and
division
Aladin offers a simple interface to compute simple
basic operations on a couple of images: addition,
subtraction, multiplication, and division. The
control window can be opened with the menu
« Image  Arithmetic operations » (accessed only if at
least two images are in the stack). Aladin will
proceed pixel by pixel by doing, if needed, a resampling of the second image so that it
corresponds to the grid of the first image (cf. 5.11). One can ask to do first a
normalisation of the pixels in the two images so that their values are located between 0
and 1 (real format). The result from the operation will be seen as a new image plane in
the pile.
Trick: If you wish to use a scalar as the second operant rather that an image –e.g. add a
given value to all pixels – you can use scripts commands: +, -, *, /(cf. )
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