Update: this function is now available at github.com/maxim/smart_resize_image.
Fork away!
Should be easy to find, right? All you want is a function that resizes an image to constraints (doesn’t care if it should scale up or down), with possibility to select if you want to keep it proportional, and possibility to use either width or height as the constraint. Also, you want it to preserve transparency damn it! Surprisingly, I was unable to find a good function that does all that, so I decided to attempt writing it. This should do it.
Features/Usage:
-
If you pass width as 0 (zero) — this function will disregard width, and use height as constraint. Same vice versa.
If you set “proportional” to false – the function will simply stretch (or shrink) the image to its full constraints.
If one of the dimensions is set to zero, and proportional set to “false” – then the image will be forced to stretch or shrink the other dimension, and disregard the zeroed dimension (leave it the same).
If proportional is set to true – the image will resize to constraints proportionally, once again, with possibility to have either width or height set to zero.
The function can use either linux “rm” command, or php @unlink. Most probably you don’t need to ever use that flag, but on some setups – @unlink won’t work due to user access restrictions.
The function will simply replace the file that you give it, with the resized file.
The function supports gif, png, and jpeg, and preserves the transparency of gif and png images.
Tested on GD version 2.0.28 only.
Essentially, everything happens just as logically expected. Please, if you see anything wrong, and you know ways to enhance, or optimize it, let me know.
Update: Thank you Joanne for finding a bug with proportional resize, and providing a great, more concise and clear solution to proportional resize. (see comments)
Update: The image transparency code was updated to a more thorough solution. See comments for info.
Update: There is a new parameter “output” which can be set to either
- “file” – overwrite the given file (default)
- “browser” – output image through http – with correct mime type
- “return” – return GD Library Image object
- or any filename of choice – save changed version to output path
Update: There is another new parameter “delete_original”. Speaks for itself.
Please, excuse a few code misalignments. Bug with coloring filter.
{
if ( $height <= 0 && $width <= 0 ) {
return false;
}
$info = getimagesize($file);
$image = '';
$final_width = 0;
$final_height = 0;
list($width_old, $height_old) = $info;
if ($proportional) {
if ($width == 0) $factor = $height/$height_old;
elseif ($height == 0) $factor = $width/$width_old;
else $factor = min ( $width / $width_old, $height / $height_old);
$final_width = round ($width_old * $factor);
$final_height = round ($height_old * $factor);
}
else {
$final_width = ( $width <= 0 ) ? $width_old : $width;
$final_height = ( $height <= 0 ) ? $height_old : $height;
}
switch ( $info[2] ) {
case IMAGETYPE_GIF:
$image = imagecreatefromgif($file);
break;
case IMAGETYPE_JPEG:
$image = imagecreatefromjpeg($file);
break;
case IMAGETYPE_PNG:
$image = imagecreatefrompng($file);
break;
default:
return false;
}
$image_resized = imagecreatetruecolor( $final_width, $final_height );
if ( ($info[2] == IMAGETYPE_GIF) || ($info[2] == IMAGETYPE_PNG) ) {
$trnprt_indx = imagecolortransparent($image);
// If we have a specific transparent color
if ($trnprt_indx >= 0) {
// Get the original image's transparent color's RGB values
$trnprt_color = imagecolorsforindex($image, $trnprt_indx);
// Allocate the same color in the new image resource
$trnprt_indx = imagecolorallocate($image_resized, $trnprt_color['red'], $trnprt_color['green'], $trnprt_color['blue']);
// Completely fill the background of the new image with allocated color.
imagefill($image_resized, 0, 0, $trnprt_indx);
// Set the background color for new image to transparent
imagecolortransparent($image_resized, $trnprt_indx);
}
// Always make a transparent background color for PNGs that don't have one allocated already
elseif ($info[2] == IMAGETYPE_PNG) {
// Turn off transparency blending (temporarily)
imagealphablending($image_resized, false);
// Create a new transparent color for image
$color = imagecolorallocatealpha($image_resized, 0, 0, 0, 127);
// Completely fill the background of the new image with allocated color.
imagefill($image_resized, 0, 0, $color);
// Restore transparency blending
imagesavealpha($image_resized, true);
}
}
imagecopyresampled($image_resized, $image, 0, 0, 0, 0, $final_width, $final_height, $width_old, $height_old);
if ( $delete_original ) {
if ( $use_linux_commands )
exec('rm '.$file);
else
@unlink($file);
}
switch ( strtolower($output) ) {
case 'browser':
$mime = image_type_to_mime_type($info[2]);
header("Content-type: $mime");
$output = NULL;
break;
case 'file':
$output = $file;
break;
case 'return':
return $image_resized;
break;
default:
break;
}
switch ( $info[2] ) {
case IMAGETYPE_GIF:
imagegif($image_resized, $output);
break;
case IMAGETYPE_JPEG:
imagejpeg($image_resized, $output);
break;
case IMAGETYPE_PNG:
imagepng($image_resized, $output);
break;
default:
return false;
}
return true;
}
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
$image_resized = imagecreate( $final_width, $final_height );
else
$image_resized = imagecreatetruecolor( $final_width, $final_height );
If someone is able to get imagecreatetruecolor() to work on gifs let me know, but I keep getting a filled in background.
a second option for dealing with GIFs is to add
imagetruecolortopalette($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).
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!
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
The parameter named
$outputaccepts any arbitrary filesystem paths.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!
Struggled with inconsistent transparency-results on a resized PNG for two hours… Solved my problem in 5min after i found your routine/example… THANKS!
Excellent work. I am using your function (along with Aaron’s fix) and it works great.
Awesome stuff! Thanks!
Now to add a watermark/branding parameter ;)
This function is good and all, but I have been looking for 3 days now on how to fill the transparent portion with a specific color. As you can probably guess, I am not all that familiar with GD.
Thanks! It works like a champ!
Ok, so I’m uploading PNG files and they are resizing correctly but coming out with a black background instead of transparency. Is that due to the way the original PNG was created or is there something I need to tweek with your code. Unfortunately I don’t know a lot about working with images like this. Any help is greatly appreciated.
Thanks!
For those who get a black background, this works perfectly with images saved as PNG 24 rather than 8. If you still get a black background and you are merging the image returned from this function on to another image then heres the problem. It took me days to figure this out and I hope it saves someone else lots of time. imagecopymerge() does NOT preserve the transparency, that is what makes it a black background, not this function, instead use imagecopy() and it will work perfectly.
There are also 2 typos in this function if you get the version from GitHub, $trnprt_indx should be $transparency and $trnprt_color should be $transparent_color
If i’d like to resize my image with 50% ? How I manage that? $width = $width/2 –> doesn’t work..
Grts
[...] [...]
An excellent function! Thanks a lot!
The only thing missing is the ability to preserve animation of animated gifs.
Very good application. I am benefited so much
I added the transparency code into my own resize function and it worked like a charm.
Thanks a lot!
it’s a really great function, but i got some problem when trying to resize big image. Here’s my code:
$id = $_GET['id']; if (is_uploaded_file($_FILES['Filedata']['tmp_name'])){
}
the idea is to duplicate the image and resize it. It’s work great with small image, but when i try to upload the image such as 3508×4961 px, it’s doesn’t work. the image size only 138kb. I’m not sure what i doing incorrectly. Please help me! Thanks a lot.
Try this before calling the resize function
ini_set(‘memory_limit’, ’128M’);
I added a couple of options it could really use like image quality and final destination path. By default your script works great but the resulting quality was pretty pixilated after the resize so I had to add the native php image quality percentage and it’s perfect now.
function smart_resize_image( $file, $width = 0, $height = 0, $proportional = true, $output = ‘file’, $delete_original = true, $use_linux_commands = false, $resizedfilename = ‘c:\photos\large’, $quality = 95)
Add $quality to:
switch ( $info[2] ) { case IMAGETYPE_GIF: imagegif($image_resized, $output, $quality); break; case IMAGETYPE_JPEG: imagejpeg($image_resized, $output, $quality); break; case IMAGETYPE_PNG: imagepng($image_resized, $output, $quality); break; default: return false; }
Thanks for the code assist, the transparency issue was one thing I was struggling with.
Declare function => function smart_resize_image( $file, $width = 0, $height = 0, $proportional = false, $output = ‘file’, $delete_original = true, $use_linux_commands = false, $degrees = 0, $rotate = false )
existing code => switch ( strtolower($output) ) { case ‘browser’: $mime = image_type_to_mime_type($info[2]); header(“Content-type: $mime”); $output = NULL; break; case ‘file’: $output = $file; break; case ‘return’: return $image_resized; break; default: break; }
New code =>
if($rotate == ‘true’ & is_numeric($degrees)){
}
useage with rotation =>
smart_resize_image( $image, $width = 200, $height = 150, $proportional = true, $output = ‘browser’, $delete_original = false, $use_linux_commands = false, $degrees = ’90′, $rotate = true );
quite simple to add really thank you for the original code though
I love you.
About to test this code out. Thanks so much, bud!
if I set the $output to file and it’s a PNG image, the save image result is a blank image. can you help me out here?
Great works cheers
take a look: http://www.codicefacile.it/smartimage/SmartImage096.zip
i’ve corrected this class with your function:
$new = imagecreatetruecolor($newwidth, $newheight);
$new = $this->saveTransparence($newwidth, $newheight);
$new = imagecreatetruecolor($w, $h);
$new = $this->saveTransparence($w, $h);
// your function: private function saveTransparence($width, $height) { $image_resized = imagecreatetruecolor($width, $height); $image = $this->gdID; if ($this->info[2] == 1 || $this->info[2] == 3) { $trnprt_indx = imagecolortransparent($image);
} return $image_resized;
}
What do you think about? P.S. the above class it's not mine... (sorry for my english i'm italian...)
i’ve commented this lines but the text-editor have removed <#>
/* $new = imagecreatetruecolor($newwidth, $newheight); */
/* $new = imagecreatetruecolor($w, $h); */
Great…!!! Its work for CodeIgniter Library.
Thanks a lot.
[...] 实际应用时，我们发现有时候小百合BBS中的图片都是几百万像素的照片原图，在校园网内访问这些图片自然是毫无压力的，而且Web版BBS中有JavaScript来自动将过大的图片强制缩小显示，以免撑破版面。但是到了外站，如此大的图片就显得有些夸张了，利用PHP中的GD图形库，我们可以方便地进行图片的二次处理，首要的需求自然是将过大的图片缩小。GD库并没有直接按比例缩小图片的功能（如果有也太高级了），好在网上早已有许多现成的代码片段，我们便无需再次发明轮子了。参考了Maxim Chernyak的代码片段，我们可以很轻松地实现这一功能。需要说明的是，原始的代码片段中对于小图片也会进行放大处理，而且它对GIF动画的处理会让它变成静止图片，因此需要对其进行小小的修改来满足我们的需要。 [...]
[...] http://mediumexposure.com/smart-image-resizing-while-preserving-transparency-php-and-gd-library/ [...]
thanks for the code dude, really helps.
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Class doesn’t work on my server. I get the following error message:
Parse error: syntax error, unexpected T_STRING, expecting T_OLD_FUNCTION or T_FUNCTION or T_VAR or ‘}’ in /home/vhosts/mysite.nl/httpdocs/096/SmartImage.class.php on line 16
You saved the day sir! thank you so much for posting this online! You’re the only person who has posted a script that actually works on PNGs with full opacity.
hearty thanks for you…
[...] Smart Image Resizing while Preserving Transparency With PHP and GD Library [...]
GREAT!!
Very good work. Thank you. :)
Nice work, thanks a lot!
Very cool, thank you so much!
There’s a typo in the code on github, instead of:
it should be:
Thanks anyway :)
Great work.. Thanks for your code.. it saved my time… :)
Are you getting black background? I was getting it for like 3 hours before I found solution. I had this problem just with some images. Some were good, some had black background. I tried to dump $trnprt_indx variable with these bad images and I was getting values less than zero! Condition if ($trnprt_indx >= 0) is meaningless. Note: I was dealing just with PNGs. Don’t know if it affects GIFs.
Works like a charm, thanks a lot.. it helped me. (y)
Thank you guys for the great posts.
You saved a lot of my hairs, I love you all :P
Thanks, your function is saved my hours. Can you added to works with gif animated please?