If you're trying to load a translucent png-24 image but are finding an absence of transparency (like it's black), you need to enable alpha channel AND save the setting. I'm new to GD and it took me almost two hours to figure this out.
<?php
$imgPng = imageCreateFromPng($strImagePath);
imageAlphaBlending($imgPng, true);
imageSaveAlpha($imgPng, true);
/* Output image to browser */
header("Content-type: image/png");
imagePng($imgPng);
?>imagecreatefrompng
(PHP 4, PHP 5, PHP 7, PHP 8)
imagecreatefrompng — Create a new image from file or URL
Description
imagecreatefrompng() returns an image identifier representing the image obtained from the given filename.
Tip
A URL can be used as a filename with this function if the fopen wrappers have been enabled. See fopen() for more details on how to specify the filename. See the Supported Protocols and Wrappers for links to information about what abilities the various wrappers have, notes on their usage, and information on any predefined variables they may provide.
Parameters
filename-
Path to the PNG image.
Return Values
Returns an image object on success, false on errors.
Changelog
| Version | Description |
|---|---|
| 8.0.0 | On success, this function returns a GDImage instance now; previously, a resource was returned. |
Examples
Example #1 Example to handle an error during loading of a PNG
<?php
function LoadPNG($imgname)
{
/* Attempt to open */
$im = @imagecreatefrompng($imgname);
/* See if it failed */
if(!$im)
{
/* Create a blank image */
$im = imagecreatetruecolor(150, 30);
$bgc = imagecolorallocate($im, 255, 255, 255);
$tc = imagecolorallocate($im, 0, 0, 0);
imagefilledrectangle($im, 0, 0, 150, 30, $bgc);
/* Output an error message */
imagestring($im, 1, 5, 5, 'Error loading ' . $imgname, $tc);
}
return $im;
}
header('Content-Type: image/png');
$img = LoadPNG('bogus.image');
imagepng($img);
imagedestroy($img);
?>The above example will output something similar to:
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User Contributed Notes 4 notes
Anonymous ¶
20 years ago
sageptr at gmail dot com ¶
3 years ago
Because gd and imagick do not support animated PNG (at this moment), i wrote a simple function to determine if given PNG is APNG or not. It does not validate PNG, only checks whenever "acTL" chunk appears before "IDAT" like the specification says: https://wiki.mozilla.org/APNG_Specification
<?php
function is_apng(string $filename): bool
{
$f = new \SplFileObject($filename, 'rb');
$header = $f->fread(8);
if ($header !== "\x89PNG\r\n\x1A\n") {
return false;
}
while (!$f->eof()) {
$bytes = $f->fread(4);
if (strlen($bytes) < 4) {
return false;
}
$length = unpack('N', $bytes)[1];
$chunkname = $f->fread(4);
switch ($chunkname) {
case 'acTL':
return true;
case 'IDAT':
return false;
}
$f->fseek($length + 4, SEEK_CUR);
}
return false;
}
?>
marcos at assl-site dot net ¶
17 years ago
I had the same problem as jboyd1189 at yahoo dot com but I solve d it allocating more memory dynamically.
Usually the memory_limit var on php.ini is set to 8M. Unfortunately, the required amount of memory to manage a PNG image about 1000x1000 could be bigger !
The approach I used to solve the problem is:
1-Calculate the memory required by the image
2-Set the new memory_limit value
3-Create the PNG image and thumbnail
4-Restore the original value
1-The following value works for me:
$required_memory = Round($width * $height * $size['bits']);
Note that for JPEG the requirements are not the same:
http://es2.php.net/manual/en/function.imagecreatefromjpeg.php#60241
2-Use somthing like:
$new_limit=memory_get_usage() + $required_memory;
ini_set("memory_limit", $new_limit);
4-ini_restore ("memory_limit");
admin at wdfa dot co dot uk ¶
15 years ago
When using imagecreatepng with alpha blending you will lose the blending.
To over come this use something like the following
<?php
$dstimage=imagecreatetruecolor($width,$height);
$srcimage=imagecreatefrompng($src);
imagecopyresampled($dstimage,$srcimage,0,0,0,0, $width,$height,$width,$height);
?>
Where $width and $height are the width and height of the $src image.
This will create a true colour image then copy the png image to this true colour image and retain alpha blending.