Comments on: Smart Image Resizing while Preserving Transparency With PHP and GD Library

By: pat

pat — Tue, 23 Feb 2010 14:15:27 +0000

Struggled with inconsistent transparency-results on a resized PNG for two hours… Solved my problem in 5min after i found your routine/example… THANKS!

By: Jeff

Jeff — Sat, 06 Feb 2010 18:44:14 +0000

I was using the thumbnail resize solution from Sitepoint’s PHP Anthology (2nd edition), and I was able to integrate your transparency handling code into it easily. Thanks!

By: hakunin

hakunin — Wed, 20 Jan 2010 09:19:42 +0000

The parameter named $output accepts any arbitrary filesystem paths.

By: Marvin S.

Marvin S. — Sat, 09 Jan 2010 18:35:51 +0000

Hey you, sorry, but i've one question. If I want to save the resized image into an thumb folder like /thumbs/, where do I have to define the output path of the saved image?

Marvin

By: Tom

Tom — Wed, 04 Nov 2009 18:25:10 +0000

My own re-size function was not properly handling transparency. I was able to integrate your transparency handling section into my function in just a couple minutes and have tested both gif and png.

Works absolutely perfect!

By: Aaron

Aaron — Wed, 28 Oct 2009 21:21:13 +0000

a second option for dealing with GIFs is to add

imagetruecolortopalette($image_resized, true, imagecolorstotal($image) );

after

imagecolortransparent( $image_resized, $trnprt_indx );

this will convert the truecolor image to a palette with the same number of colors as the original image.

FYI: GIFs are images based on the 256 color palette, imagecreatetruecolor() creates an image based on 1.6 million colors (or so).

By: Aaron

Aaron — Wed, 28 Oct 2009 20:03:19 +0000

Thank you for providing some great code… However, after trying to resize some transparent gifs for the past few days I finally noticed from php.net that imagecreatetruecolor() does not work with gifs.

so I added

if ( $info[2] == IMAGETYPE_GIF )
$image_resized = imagecreate( $final_width, $final_height );
else
$image_resized = imagecreatetruecolor( $final_width, $final_height );

If someone is able to get imagecreatetruecolor() to work on gifs let me know, but I keep getting a filled in background.

By: Sanjeev

Sanjeev — Thu, 08 Oct 2009 07:09:10 +0000

it really works great as i tried for png. But for gif image it dint gave the output as i expected. May be the original image 360×211 in dimension, while i was resizing to 300×300(with aspect ratio maintained) it gave kind of zigzag colored image

By: XRumerTest

XRumerTest — Thu, 17 Sep 2009 23:46:29 +0000

Hello. And Bye.

By: Anonymous

Anonymous — Thu, 17 Sep 2009 06:37:10 +0000

thanks 4 the lesson and .. you figured the stuff about transparency transfer ; that are not pointed out in the majority of php png manipulation methods.

P.S. png transparency thumbnail alpha blend png resize resizing tool function