[vtkusers] Linear interpolation as implemented by vtkImageReslice

[Luca Pamparana]

Hi everyone,

I had asked this question a few days back but did not receive any
help. Asking it again hoping someone would answer my query!

Just trying to understand the linear interpolation algorithm as
implemented in the vtkImageReslice class. I tried looking at the
source code but it is
really complicated and I could not understand much :(

Anyway, I am zooming my image by a factor of 2. The image is a
synthetic image which has a thick edge going along its diagonal (the
value is changing
from 0 to 255) and I am trying to look at how the values are
interpolated in that region.

One thing I noticed is that there are 2 pixels being inserted in the
horizontal direction. So, I get the values 255, 191, 64 and 0 (255 and
0 are
the old values and the two new values are being generated by taking a
weighted average).  Is this correct? I thought that if I zoom by a
factor of
2.0 than one pixel should be inserted between successive pixels. I am
not sure what happens at the edge pixels though.

Also, what happens in the vertical direction? I cannot really figure
out how this works...

So if I have pixel values as follows:

255    0    1    2
0      255  0    1

How is the lienar interpolation being done on a zoom of 2.0?

I would really appreciate it if someone can clarify these doubts for
me.... I have spend a lot of time trying to understand this but have
not yet been able to comprehend this implementation.

Thanks,

Luca
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