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)
imagecreatefrompng — Creează o imagine nouă din fișier sau din URL
Descrierea
imagecreatefrompng
( string
$filename
) : resourceimagecreatefrompng() returns an image identifier representing the image obtained from the given filename.
Sfat
Un URL poate fi utilizat în calitate de denumire a fișierului în această funcție dacă învelișurile fopen au fost activate. Accesați fopen() pentru mai multe detalii despre modul de specificare a denumirii fișierului. Accesați Supported Protocols and Wrappers pentru referințe la informații despre posibilitățile pe care le oferă diferite învelișuri, note despre utilizarea lor și informații despre variabile predefinite pe care le oferă.
Parametri
-
filename -
Path to the PNG image.
Valorile întoarse
Întoarce un identificator de resursă de tip
imagine în cazul succesului, false în caz de erori.
Exemple
Example #1 Example to handle an error during loading of a PNG
<?php
function LoadPNG($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);
?>
Exemplul de mai sus va afișa ceva similar cu:
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User Contributed Notes 7 notes
Anonymous ¶
20 years ago
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");
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;
}
?>
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 $src image.
This will create a true colour image then copy the png image to this true colour image and retain alpha blending.
Cyrille37 ¶
9 years ago
The image size (width x height) should not exceed INT_MAX ... It's still thrue on a 64 bits computer.
katalin at knittedforyou dot com ¶
7 years ago
I have this code:
if (exif_imagetype($this->img_name) == IMAGETYPE_PNG) {
try {
$this->image = imagecreatefrompng($this->img_name);
Error::log('It is a png: '.$this->img_name);
} catch (Exception $e) {
echo "The image file has some strange charachters. Probably not a png image?";
$this->image = '';
$this->img_name = '';
}
}
And I get this error in the error.log:
PHP Unknown error: imagecreatefrompng(): gd-png: fatal libpng error: Extra compressed data\n in Unknown on line 0
The file that I try to open is a generated .png image which I can open from gimp and Geeqie.
What is the problem? Could you please help me?
jboyd1189 at yahoo dot com ¶
18 years ago
I was having a terrible time with the imagecreatefrompng function as it was working perfectly for one image and not at all for another. After many hours of frustration, I discovered that the problem was the image size (number of pixels). It appears that the maximum number of pixels this function will process is 1,040,000. So, be sure that the pixel resolution of the image (eg. 1040 x 1000) does not exceed this value.
