Sorry, didn't notice the 50% *shrinkage* in the other direction.
You'll of course
want to use "pdl(0.5,2)" in the bottom example, or add the
appropriate line in the top
example.
You may want to play with the different resampling algorithms in map
(), to highlight
the weirdnesses of the Baker transform -- vertical Fourier components
are shoved way,
way up above the Nyquist frequency, so you ought to get some
interesting effects with the
"sample" method, while the "hanning" or "gaussian" methods ought to
be more correct but
less interesting.
On Aug 31, 2007, at 8:13 AM, Craig DeForest wrote:
Hi, Hernan,
You can specify scale independently by feeding a vector into the
"scale=>"
field of the t_linear parameters. More easily, you can use
PDL::Transform's
autoscaling features:
$x = rim("my_image_original.png");
$xdims = [$x->dims];
$xdims->[1] *= 2;
$y = $x->map( t_identity, $xdims );
You can compress the last three lines into one:
$y = $x->match( [(pdl($x->dims)*pdl(1,2))->list] );
Cheers,
Craig
On Aug 31, 2007, at 7:10 AM, Hernán De Angelis wrote:
Dear listers,
I am trying to write a small program in PDL that performs the "baker"
transformation on a sample image. I am a relatiovely new PDL user and
the objective of this is to learn more The basic steps, given an
image, are:
1. 100% stretch in the X direction, e.g. from 100 pixels to 200.
2. 50% contract in the Y direction, e.g. from 100 pixels to 50.
3. divide in two halves along X and create a new image by putting the
right halve above the left one (the new image has the same size as
the
input one).
I know how to do step number 3, but my attempts to use PDL::Transform
to do steps 1 and 2 have failed. Basically, I cannot figure out
how to
define a transformation (using t_linear) that applies different
scales
to X and Y. Any hint will be appreciated.
Thanks in advance
Hernán
--
Hernán De Angelis
Linux user # 397217
_______________________________________________
Perldl mailing list
[email protected]
http://mailman.jach.hawaii.edu/mailman/listinfo/perldl
_______________________________________________
Perldl mailing list
[email protected]
http://mailman.jach.hawaii.edu/mailman/listinfo/perldl
