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determining size of image

by Anonymous Monk
on Feb 22, 2007 at 17:00 UTC ( #601588=perlquestion: print w/replies, xml ) Need Help??

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I know how to get the size of an image via Image::Info, but I want to add a little snippet that does a little more.

I have a picture posting site where users can upload images to and some are too large and ends up making horizontal scrollbards on the browser (not acceptable!). I can now detect which images are larger than 800x600, which is what I want to test against, but how can I dynamically resize the HTML renderation of the image?

I'm NOT trying to resize the image itself, just the HTML code of the image. Ie. <code> I'm just using HTML to make it appear smaller on screen so the user can click the image to make it appear full in a new window.

So let's say the image was 1100x900, I want to use the HTML image size to show the image at the first size in which both dimensions are smaller than my required size (800x600). In short, I want the resize to be proportioned to the size of the image itself. I COULD just resize everything that's too large to 800x600 but that'd cause a lot of crappy images, I want to keep the same proportions.

Can anyone help me with this?

Replies are listed 'Best First'.
Re: determining size of image
by ikegami (Patriarch) on Feb 22, 2007 at 17:06 UTC
    my ($width, $height ) = ...; my ($max_width, $max_height ) = (800, 600); my ($width_factor, $height_factor) = ($max_width/$width, $max_height/$ +height); if ($width_factor < 1 || $height_factor < 1) { my $factor = ($width_factor < $height_factor ? $width_factor : $height_factor ); $width = int($width * $factor + 0.5); $height = int($height * $factor + 0.5); }

    The above was extracted from a script I use to resize images.

Re: determining size of image
by zentara (Archbishop) on Feb 22, 2007 at 17:22 UTC
    Just as an aside, the ImageMagick ping method is the most efficient way to get size.
    #!/usr/bin/perl -w use Image::Magick; my $x = $ARGV[0]; my $image = Image::Magick->new; #$image->Read($x); #my ($w,$h)= $image->Get('columns','height'); #print $x,' is ',$w.'x'.$h,"\n"; #this is very inneficient memory wise, use Ping ($width, $height, $size, $format) = $image->Ping($x); print $width,"\n", $height,"\n" ,$size,"\n", $format,"\n";
    and here is a script I had in my library to do an actual distortion free resize.
    #!/usr/bin/perl # I need to adjust an image to a minimum size, but without distoring i +t, # so I basically want to add space evenly around the existing image. # Using Resize is out since that will distort the image, so I gave # "Composite" a shot, use Image::Magick; use strict; use warnings; my $im = Image::Magick->new(); my $bg = Image::Magick->new(size => "200x400"); my $rc = $bg->Read("xc:white"); $rc = $im->Read($ARGV[0]); die $rc if $rc; $rc = $im->Resize("200x400"); warn $rc if $rc; $rc = $bg->Composite(gravity => "Center", image => $im); warn $rc if $rc; $rc = $bg->Write("$ARGV[0]-resized.png"); die $rc if $rc;

    I'm not really a human, but I play one on earth. Cogito ergo sum a bum
Re: determining size of image
by dorward (Curate) on Feb 22, 2007 at 17:19 UTC

    I'm NOT trying to resize the image itself, just the HTML code of the image.

    I suggest not doing that. Browsers suck at scaling images, and transfering all those bytes across a network just to have detail thrown away is a waste of bandwidth.

Re: determining size of image
by kwaping (Priest) on Feb 22, 2007 at 17:42 UTC
    Of course, there's always Image::Size. :)

    ---
    It's all fine and dandy until someone has to look at the code.
Re: determining size of image
by mreece (Friar) on Feb 22, 2007 at 18:53 UTC
    i typically use something like the following (using Image::Size)
    use Image::Size; my ($w, $h) = imgsize("blort.jpg"); if ($w > 800) { my $f = $w / 800; $w = int($w/$f); $h = int($h/$f) }; if ($h > 600) { my $f = $h / 600; $w = int($w/$f); $h = int($h/$f) };

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