Resize PNGs with php Imagick preserving background

Question

I am trying to resize images using cropThumbnailImage. I use cropThumbnailImage as it resizes to the shorter length of the original image and crops the image on the longer side equally on both sides so that center portion of the image remains uncropped. This works fine for jpg images but for png images, the resized pngs get a black background.

Following is the code I use.

    $image = new \Imagick($src);

    // resize & crop
    $image->cropThumbnailImage($width, $height);

    // save new resized file
    $image->writeImage($dest);

Run this code for the following png image.

http://tuxpaint.org/stamps/stamps/animals/birds/cartoon/tux.png http://www.cs.csubak.edu/~mcabrera/CS211/transparent.png http://www.tcarms.com/media/assets/productPhotos/006_G2%20Contender/png/Pistol_12in_Ribbed_Blued_2720.png

The output image is resized as required but the png image gets black background.

Tried adding below lines from herebut did not work.

imagealphablending( $image, false );
imagesavealpha( $image, true );

There are other solutions out there in the web which achieve resizing of png images, but I did not find a solution that resizes image the way cropThumbnailImage does.

Aaaand what exactly do you expect? There is no transparency in JPEGs. — Carsten, Jun 25 '13 at 11:53
Google harder? I just did a Google search and came up with a few useful results on my first try. Check your version number as well. And as Carsten said, you're using jPEG compression of PNG image. JPEG does not support transparency. — BLaZuRE, Jun 25 '13 at 11:54
JPGs are not transparent... Please refer to PNGs and Gifs files... — NETCreator Hosting - WebDesign, Jun 25 '13 at 11:55
Your code: COMPRESSION_JPEG - JPEG is not PNG, it is without transparency. With this code you convert the PNG into JPEG. You MUST maintan the extension if you want to have transparency... — NETCreator Hosting - WebDesign, Jun 25 '13 at 12:05
Thanks all for pointing out the compression. I removed it and tested. the image still seems to be getting a black background. — Venkat Kotra, Jun 25 '13 at 12:12
Thanks @BLaZuRE for pointing out the jpeg compression issue. I should probably check the image format before doing this. Any ways I still get the issue. — Venkat Kotra, Jun 25 '13 at 12:13
@ITChristian I have edited my code. Not compressing with COMPRESSION_JPEG. Can you please point me in right direction for resizing transparent png images. — Venkat Kotra, Jun 25 '13 at 12:21
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/32337/discussion-between-venkat-kotra-and-itchristian) — Venkat Kotra, Jun 25 '13 at 12:44
Why is this question closed ? Am willing to add more details to get the question answered. — Venkat Kotra, Jun 25 '13 at 14:03
@ITChristian Thanks for your time. This code doesnt seem to be working yet. — Venkat Kotra, Jun 25 '13 at 14:35

score 2 · Answer 1 · answered Sep 07 '16 at 17:38

2

Transparency is preserved using the following snippet:

$im = new Imagick($imgPath);
$im->setImageFormat('png');
$im->writeImage('/files/thumbnails/new_title.png');

answered Sep 07 '16 at 17:38

zeros-and-ones

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score 0 · Accepted Answer · edited Jun 20 '20 at 09:12

There is not transparency in your JPG... The JPG is not a transparent image... PNG and GIF are necessary here.
If you are refering to PNG, there is a PHP code who will help you to resize PNGs with transparency:

$x = "COORDINATES - X for crop";

$y = "COORDINATES - y for crop";

$w = "width";

$h = "height";

$img = imagecreatefrompng($img_path);

imagealphablending($img, true);

$img_cropped = imagecreatetruecolor($w, $h);

imagesavealpha($img_cropped, true);

imagealphablending($img_cropped, false);

$transparent = imagecolorallocatealpha($img_cropped, 0, 0, 0, 127);

imagefill($img_cropped, 0, 0, $transparent);

imagecopyresampled($img_cropped, $img, 0, 0, $x, $y, $w, $h, $w, $h); // you can also use imagecopy() here

imagepng($img_cropped, "your_image_cropped.png", 2);

imagedestroy($img);

imagedestroy($img_cropped);

EDIT: Try this:

$image = imagecreatefrompng ( $filename );

$new_image = imagecreatetruecolor ( $width, $height ); // new wigth and height

imagealphablending($new_image , false);

imagesavealpha($new_image , true);

imagecopyresampled ( $new_image, $image, 0, 0, 0, 0, $width, $height, imagesx ( $image ), imagesy ( $image ) );

$image = $new_image;

// saving

imagealphablending($image , false);

imagesavealpha($image , true);

imagepng ( $image, $filename );

Don't forget to define $filename, $width, $height!!!!

The question asks how to resize png's using Imagick, not GD library. — zeros-and-ones, Sep 07 '16 at 17:21
this will cause a grey border when resizing images with semi transparent pixels — Ruttyj, Aug 31 '18 at 01:58

Resize PNGs with php Imagick preserving background

2 Answers2