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($imgPng);
?>
imagecreatefrompng
(PHP 4, PHP 5, PHP 7, PHP 8)
imagecreatefrompng — 新しい画像をファイルあるいは URL から作成する
説明
imagecreatefrompng()は引数 filename から得られる画像を表す画像 ID を返します。
ヒント
fopen wrappers が有効の場合、この関数のファイル名として URL を使用することができます。ファイル名の指定方法に関する詳細は fopen() を参照ください。 サポートするプロトコル/ラッパー には、さまざまなラッパーの機能やその使用法、 提供される定義済み変数などの情報がまとめられています。
パラメータ
-
filename -
PNG 画像へのパス。
戻り値
成功した場合に画像オブジェクト、エラー時に false を返します。
例
例1 PNG の作成時のエラーを処理する例
<?php
function LoadPNG($imgname)
{
/* オープンします */
$im = @imagecreatefrompng($imgname);
/* 失敗したかどうかを調べます */
if(!$im)
{
/* 空の画像を作成します */
$im = imagecreatetruecolor(150, 30);
$bgc = imagecolorallocate($im, 255, 255, 255);
$tc = imagecolorallocate($im, 0, 0, 0);
imagefilledrectangle($im, 0, 0, 150, 30, $bgc);
/* エラーメッセージを出力します */
imagestring($im, 1, 5, 5, 'Error loading ' . $imgname, $tc);
}
return $im;
}
header('Content-Type: image/png');
$img = LoadPNG('bogus.image');
imagepng($img);
imagedestroy($img);
?>上の例の出力は、 たとえば以下のようになります。
add a note
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.
