imgscale

#!/usr/bin/perl

# Usage: imgscale w h wr hr
# w = starting image width
# h = starting image height
# wr:hr = desired ratio of final scaled size
# Use case: You want to take an image, say of 939 x 627 pixels,
# and scale it to exactly wr:wh ratio.
#
# Example:
# $ ./imgscale 939 627 6 4
# Starting with 'even' w:h = 936:624
# This ratio works perfectly: 936 wide by 624 high
#
# $ ./imgscale 939 623 6 4
# Starting with 'even' w:h = 936:620
# This ratio works perfectly: 930 wide by 620 high
#
# $ ./imgscale 939 627 3 2
# Starting with 'even' w:h = 939:626
# This ratio works perfectly: 939 wide by 626 high

my $w = shift(@ARGV);
my $h = shift(@ARGV);
my $wr = shift(@ARGV);
my $hr = shift(@ARGV);
$done = 0;

# First, get $w to be perfectly divisible by $wr
while ($w % $wr != 0) {
    $w = $w-1;
}

# And get $h to be perfectly divisible by $hr
while ($h % $hr != 0) {
    $h = $h-1;
}

print "Starting with 'even' w:h = $w:$h\n";

while (($done == 0) && ($w >= 0)) {
    # Check if the ratio works out perfectly; if so, stop
    if ($w * $hr == $h * $wr) {
	print "This ratio works perfectly: $w wide by $h high\n";
	$done = 1;
    }
    else {
	$w = $w - $wr;
    }
}