Perl Image Resize using GD and maintain image quality

Question

I am trying to resize the image using GD image library and perl, but when it is resized the quality of image is not same as original uploaded image.. Do you guys have any suggestion?

Below is my code

my $dest_w = $width;
my $dest_h = $width * ($h / $w);

my $dest = GD::Image->new($dest_w, $dest_h, 1);

$dest->copyResampled($src, 0, 0, 0, 0, $dest_w, $dest_h, $w, $h);

open OUT, ">$target" or die "Could not save to $target";
binmode OUT;
print OUT $img->jpeg($quality); 
close OUT;

Anything wrong with my code? thanks for advice

Note: I uploaded .png image. Even if uploaded .jpeg image, the quality of the image is also dropped

You're doing a no-op resize of a JPEG. Yes, this is going to cause quality degredation, because it's a JPEG. — Charles, Dec 10 '13 at 03:29
Hi Charles, what should I do with my code? thanks for advice — Lucky-Ong Ong, Dec 10 '13 at 03:37
What's your *source* image type? If it's a palette based image, the result will be worse than if it's a trueColor image. You should set GD to default to trueColor images. — Joe Z, Dec 10 '13 at 04:35
I tried .png and .jpeg image, both give me same result (bad image quality).. — Lucky-Ong Ong, Dec 10 '13 at 04:52
@Lucky-OngOng: When you loaded the JPEG, did you tell GD to load it as trueColor? — Joe Z, Dec 10 '13 at 06:21
yes... GD::Image->new($dest_w, $dest_h, 1); parameter 1 is telling GD to load as true color — Lucky-Ong Ong, Dec 10 '13 at 10:25

score 1 · Answer 1 · answered Dec 20 '15 at 18:57

Do you have to use GD? If you use GD to resize an input image eg a .jpg in Perl even with

my $quality = 100;
print OUT $resultimage->jpeg($quality);

then at least in its present versions, as I have tested them just now, both GD and Imlib2 (also there quality set to 100) produced somewhat more blur than such as ImageMagick in Perl. In addition, best results come if resized jpg image is saved to .gif (or .png), eg:

#! /usr/bin/perl
use Image::Magick;
my($inimage, $resultimage, $info);
$inimage = Image::Magick->new;
$info = $inimage->Read('exampleimagebig.jpg');
warn "$info" if "$info";
$info = $inimage->Resize(geometry=>'500x500', blur=>0.9);
warn "$info" if "$info";
# In the next line you can write .png or if you must, .jpg:
$info = $inimage->Write('exampleimage500.gif');
warn "$info" if "$info";

score 0 · Answer 2 · answered Jan 07 '14 at 07:10

0

Try define $quality as in my example and try it with png on input.

binmode OUT;
$quality=100; 
print OUT $img->jpeg($quality);

answered Jan 07 '14 at 07:10

Sergiy Zaschipas

134
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Perl Image Resize using GD and maintain image quality

2 Answers2