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## Transformers -- Structural changes (data re-arrangements)
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## Warping by means of a general projective transform
operator op::transform::by {
section transform structure warp
example {
bframe [dot red {10 50} [butterfly]] |
aktive transform rotate by 30 around {10 50} | -matrix -label rotate by 30 around {10 50}
@2 @1 | bframe
}
example {
butterfly |
aktive transform scale x 0.5 y 1.5 | -matrix -label scale x 0.5 y 1.5
@2 @1
}
example {
butterfly |
aktive transform shear x 20 y 10 | -matrix -label shear x 20 y 10
@2 @1
}
example {
butterfly |
aktive transform reflect x | -matrix -label reflect x
@2 @1
}
example {
butterfly |
aktive transform reflect y | -matrix -label reflect y
@2 @1
}
example {
bframe [line red {50 260} {150 -10} [butterfly]] |
aktive transform reflect line a {50 260} b {150 -10} | -matrix -label reflect line {50 260} b {150 -10}
@2 @1 | bframe
}
# !xref-mark affine location marker
# !xref-mark affine
example {
dot green {190 10} [dot blue {210 80} [dot red {47 62} [poly red {{47 62} {190 10} {210 80} {100 125} {47 62}} [butterfly]]]] |
aktive transform quad 2quad a {47 62} b {190 10} c {210 80} d {100 125} e {0 0} f {100 0} g {100 100} h {0 100} | -matrix -label quadrilateral
aktive op transform by @2 @1
aktive op view @3 port {0 0 100 100}
}
# !xref-mark /end
note Applies the projective __forward__ `transform` to the source image, \
using some kind of pixel interpolation, and returns the result. \
The default interpolation is `bilinear`.
note The necessary backward transformation is computed internally.
note The result's domain is set to the domain of the \
forward transform applied to the input domain. \
Fractions are rounded to integers such that the actual \
bounding box is kept enclosed.
note The result has depth of the image.
note See "<!xref: aktive transform affine>" and its relatives \
for a set of operations creating transformations acceptable \
here.
note The "<!xref: aktive op view>" operator is a useful means of focusing \
on the desired part of a transformation result.
strict 1st \
The projective matrix is materialized for the calculation of \
the backward transform.
str? bilinear interpolate Interpolation method to use
input transform Affine forward transformation.
input src The image to transform.
body {
lassign [aktive transform domain $transform $src] x y w h
set backward [aktive transform invert $transform]
set origin [aktive warp matrix $backward x $x y $y width $w height $h]
aktive op warp $interpolate $origin $src
}
}
##
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::return