Error when showing image with GD

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Error when showing image with GD

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#1 by (2 votes)

-4

I'm trying to display a PNG image on the client browser screen using PHP, but only a black screen with a comic in the center appears.

What am I doing wrong? Here is my code:

<?php

        $file  = "img.png";
        $width = 500;
        $height= 500;

        list($width_origin,$height_origin) = getimagesize($file);
        $ratio = $width_origin / $height_origin;

        if ($width/$height > $ratio) {
            $width = $height * $ratio;
        }else{
            $height = $width / $ratio;
        }

        $image_final  = imagecreatetruecolor($width, $height);
        $imagem_origin= imagecreatefrompng($file);
        imagecopyresampled($image_final,$imagem_origin,0,0,0,0,$width,$height,$width_origin,$height_origin);
        header("Content-type: image/png");
        imagepng($image_final,"imagem_nova.png");


    ?>

php gd

asked by anonymous 27.01.2017 / 08:16

1 answer

Check which is greater using a formula in python [closed] Error executing mysql_query [closed]

score 2 · Accepted Answer

If you put the second parameter in imagepng it will not display and save, it's as described in the documentation link

If not set or NULL, the raw image stream will be outputted directly.

In other words, if the second parameter is not set or it is NULL it will display, otherwise it will save to a file.

So whenever in doubt, search the documentation and read how to use each parameter and see the examples. In case your code should look like this:

<?php

$file  = "img.png";
$width = 500;
$height= 500;

list($width_origin, $height_origin) = getimagesize($file);

$ratio = $width_origin / $height_origin;

if ($width/$height > $ratio) {
    $width = $height * $ratio;
}else{
    $height = $width / $ratio;
}

$image_final  = imagecreatetruecolor($width, $height);
$imagem_origin= imagecreatefrompng($file);
imagecopyresampled($image_final,$imagem_origin, 0, 0, 0, 0, $width, $height, $width_origin, $height_origin);
header("Content-Type: image/png");

imagepng($image_final); //Exibe a imagem

If you want to view and save at the same time, you can use several methods, such as saving to a stream or file directly:

Using readfile :

if (imagepng($image_final, $file)) //salva para um arquivo
{
    header("Content-Type: image/png");
    readfile($file);
} else {
    echo 'Erro ao salvar';
}

fopen + stream_get_contents

This is a little more complicated, but if you need to do some manipulation in the stream it might be interesting to use it.

$handle = fopen($handle, 'wb');

if (!$handle) {
    die('Erro ao abrir o arquivo para escrita');
}

if (imagepng($image_final, $handle)) //salva para um arquivo
{
    header("Content-Type: image/png");
    echo stream_get_contents($handle);
} else {
    echo 'Erro ao salvar';
}

fclose($handle);

What each parameter does:

The function is basically

bool imagepng ( resource $image [, mixed $to [, int $quality [, int $filters ]]] )

$image

It should be an resource of an image, returned by image-authoring functions, for example imagecreatetruecolor() , imagecreatefrompng() , etc.
$to

The path or an open stream (which will be automatically closed when the function returns) to save the file. If not set or is NULL , the image will be displayed in the output.
$quality

Compression level: if 0 (no compression) up to 9.
$filters

Lets you reduce the size of the PNG file. This is a bitmask field which you can set any combination of constants PNG_FILTER_XXX . If you use PNG_NO_FILTER or PNG_ALL_FILTERS or use them respectively will disable or enable all filters.