Preserve PNG transparency while resizing with out the black background

Question

I have a small class which handles image manipulation.

I use following to resize a image

$this->image = imagecreatefrompng($filename);
....
$new_image = imagecreatetruecolor($width, $height);
imagecopyresampled($new_image, $this->image, 0, 0, 0, 0, $width, $height, $this->getWidth(), $this->getHeight());
...
$this->image = $new_image; 
imagepng($this->image,$filename)) { return true; }

But the resized image is not preserving transparency, instead black is comming, how can i preserve the transparency.

Update

After, using @Manuel's code, black portion has decreased, but still black background are still present. The source image and the resulting image are

Source & Sub corresponding

main http://www.freeimagehosting.net/newuploads/820a0.png sub http://www.freeimagehosting.net/newuploads/30526.png

you should check [this post](http://stackoverflow.com/questions/313070/png-transparency-with-php) — , Oct 18 '11 at 11:56

score 3 · Answer 1 · edited Jul 16 '16 at 17:21

3

The newest comment, posted on the 8th of May, on the manual page for imagecopyresampled, tells you how to do this.

imagecolortransparent($new_image, imagecolorallocatealpha($new_image, 0, 0, 0, 127));
imagealphablending($new_image, false);
imagesavealpha($new_image, true);

Put that right after creating $new_image.

edited Jul 16 '16 at 17:21

answered Oct 18 '11 at 11:58

Niet the Dark Absol

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what doesw that $new contain. will this work for all types, or just pngs – mrN Oct 18 '11 at 12:15

score 1 · Answer 2 · answered Oct 18 '11 at 11:58

1

add this before the imagecopyresampled(...)

// preserve transparency
imagecolortransparent($new_image , imagecolorallocatealpha($new_image , 0, 0, 0, 127));
imagealphablending($new_image , false);
imagesavealpha($new_image , true);

answered Oct 18 '11 at 11:58

Manuel van Rijn

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but i am still getting black bgs, but is less amount that before – mrN Oct 18 '11 at 12:42
Ok, you can check the update, thats the result after using your code. – mrN Oct 18 '11 at 14:28

Preserve PNG transparency while resizing with out the black background

Update

2 Answers2