| Subject: | det operator for transform2 + sample |
| Date: | Thu, 6 Dec 2007 10:32:08 +1100 |
| To: | bugs-Imager [...] rt.cpan.org |
| From: | Tony Cook <tony [...] develop-help.com> |
----- Forwarded message from Richard Fairhurst <richard@systemeD.net> -----
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Date: Wed, 05 Dec 2007 22:09:33 +0000
From: Richard Fairhurst <richard@xxx>
To: tony@imager.perl.org
Subject: Straightening images with transform2
X-MIME-Autoconverted: from quoted-printable to 8bit by develop-help.com id lB5M9lnj009169
Hello again Tony,
Thought I'd let you know what I've been doing with Imager now it's
working on my Mac!
I've been using it to rectify ("square up") a load of roughly scanned
maps, so that an arbitrary quadrilateral is resized into a square. The
transform2 function is ideal for that.
To make the expression shorter, I added a simple determinant function
to the parser:
* in regmach.h:
rbc_det, /* det(ra, rb, rc, rd) -> r */
* in regmach.c:
case rbc_det:
nout = na*nd-nb*nc;
break;
Then this code to transform it:
---cut---
#!/usr/bin/perl -w
# Convert quadrilateral to square
use Imager;
$src=Imager->new();
$src->open(file=>"oldmap_200px.jpg");
# example co-ordinates of quadrilateral
$x0=12; $y0=4; # top left
$x1=157; $y1=0; # top right
$x2=140; $y2=150; # bottom right
$x3=27; $y3=159; # bottom left
$code=<<EOF;
xa=((h-y)*x0+y*x3)/h; ya=((h-y)*y0+y*y3)/h;
xb=((h-y)*x1+y*x2)/h; yb=((h-y)*y1+y*y2)/h;
xc=((w-x)*x0+x*x1)/w; yc=((w-x)*y0+x*y1)/w;
xd=((w-x)*x3+x*x2)/w; yd=((w-x)*y3+x*y2)/w;
d=det(xa-xb,ya-yb,xc-xd,yc-yd);
d=if(d==0,1,d);
px=det(det(xa,ya,xb,yb),xa-xb,det(xc,yc,xd,yd),xc-xd)/d;
py=det(det(xa,ya,xb,yb),ya-yb,det(xc,yc,xd,yd),yc-yd)/d;
return getp1(px,py);
EOF
$newimg=Imager::transform2({
expr=>$code,
width=>200,
height=>200,
constants=>{x0=>$x0,y0=>$y0,
x1=>$x1,y1=>$y1,
x2=>$x2,y2=>$y2,
x3=>$x3,y3=>$y3}},
($src));
$newimg->write(file=>"output_imager.jpg");
---cut---
Thought you might be interested to see what people are doing with
Imager - feel free to include this in the sample code.
Best wishes
Richard
Show quoted text
----- End forwarded message -----