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 — Crea una nueva imagen a partir de un fichero o de una URL
Descripción
resource imagecreatefrompng
( string
$filename
)imagecreatefrompng() devuelve un identificador de imagen que representa la imagen obtenida desde el nombre de fichero dado.
Sugerencia
Se puede emplear un URL como nombre de fichero con esta función si las envolturas de fopen han sido activadas. Véase fopen() para más información de cómo especificar el nombre de fichero. Véanse las Protocolos y Envolturas soportados; continen enlaces con información sobre las diferentes capacidades que tienen las envolturas, notas sobre su empleo, e información de cualquier variable predefinida que podría proporcionarse.
Parámetros
-
filename -
Ruta de la imagen PNG.
Valores devueltos
En caso de éxito, devuelve un identificador de recurso de imagen, y FALSE en caso de error.
Ejemplos
Ejemplo #1 Ejemplo de manejar un error durante la carga de un PNG
<?php
function CargarPNG($imagen)
{
/* Intentar abrir */
$im = @imagecreatefrompng($imagen);
/* Ver si falló */
if(!$im)
{
/* Crear una imagen en blanco */
$im = imagecreatetruecolor(150, 30);
$fondo = imagecolorallocate($im, 255, 255, 255);
$ct = imagecolorallocate($im, 0, 0, 0);
imagefilledrectangle($im, 0, 0, 150, 30, $fondo);
/* Imprimir un mensaje de error */
imagestring($im, 1, 5, 5, 'Error cargando ' . $imagen, $ct);
}
return $im;
}
header('Content-Type: image/png');
$img = CargarPNG('falso.image');
imagepng($img);
imagedestroy($img);
?>
El resultado del ejemplo sería algo similar a:
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User Contributed Notes 5 notes
Anonymous ¶
13 years ago
marcos at assl-site dot net ¶
10 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 ¶
8 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 ¶
1 year ago
The image size (width x height) should not exceed INT_MAX ... It's still thrue on a 64 bits computer.
jboyd1189 at yahoo dot com ¶
11 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.
