Image::Magick scale smaller makes file size bigger

[Gary Mayor]

Hi,
I know this should be in the modules group but as there seems to be a
lack of anyone else having this problem I thought i'de better give it
better coverage.
The problem is i'm using Image Magick to create thumbnails smaller
images out of large ones. 99% of the time this works great but there's
1% where the thumbnail has a bigger file size then the original image
and that I can't understand. The code i'm using is below and I hope
someone knows what this might be. I've tried resizing and saving the
images in gimp and the sizes turn out correct. Also if I compress the
image the size does decrease but why would a image with no compression
turn out bigger than the original. I also tried adding the icmp or
whatever it was to the code but that didn't make any difference. How can
this be anyone know?

Thanks

Gary

my $imager = Image::Magick->new;
die unless ref $imager;

my $status = $imager->Read("$infile");
print "Read: $status\n" if $status;

$height = $imager->Get('height');
$width = $imager->Get('width');

my $ttwidth = 100;

my $tbheight=1;
my $tbwidth=1;
my $fixed=$ttwidth;
my $scalefix=1;
my $scalefactor=$width/$fixed;
$tbheight=$height/$scalefactor;
$tbwidth=$fixed;

$count++;
$original[$count] = $cfile;
$status = $imager->Write(filename=>"$dir/$cfile");

$imager->Scale( width=>$tbwidth, height=>$tbheight );

$imager->Set(Quality=>$compression);

$new[$count] = "$outfile";
$status = $imager->Write(filename=>"$dir/$outfile",compression=>'JPEG');

 

[gnari]

Hi,
I know this should be in the modules group but as there seems to be a
lack of anyone else having this problem I thought i'de better give it
better coverage.

there are a lot of other groups with much greater coverage, where these
questions are equally off-topic.

The problem is i'm using Image Magick to create thumbnails smaller
images out of large ones. 99% of the time this works great but there's
1% where the thumbnail has a bigger file size then the original image
and that I can't understand.

that is entirely possible. when making a thumbnail, the sofware might
be doing a lot of processing to make the smaller image recognizable.
this may include playing with color depth or dithering. the rsulting
image may not compress as effectively as the original

... Also if I compress the
image the size does decrease but why would a image with no compression
turn out bigger than the original.

i do not know what you are talking about. was the original jpeg with
0 compression?

anyways some of the graphics newsgroups might be a better place
for this kind of questions. (unless, of course, if this only happens
with Image::Magick , but not the Imagemagick commandline tools)


gnari