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POMy PNG has transparency, but after saving with PHP GD, transparency is lost
 

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  1. POMy PNG has transparency, but after saving with PHP GD, transparency is lost
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    <p>I found the solution to my problem. See below the original post and completely at the bottom my solution. I made a stupid mistake :)</p> <hr> <p>First I crop an image and then save it to a png file. Right after this, I also show the image.<br> However, the saved png does not have transparency and the shown one has. What is going on?</p> <pre><code>$this-&gt;resource = imagecreatefrompng($this-&gt;url); imagealphablending($this-&gt;resource, false); imagesavealpha($this-&gt;resource, true); $newResource = imagecreatetruecolor($destWidth, $destHeight); imagealphablending($newResource, false); imagesavealpha($newResource, true); $resample = imagecopyresampled($newResource,$this-&gt;resource,0,0,$srcX1,$srcY1,$destWidth,$destHeight,$srcX2-$srcX1, $srcY2-$srcY1); imagedestroy($this-&gt;resource); $this-&gt;resource = $newResource; // SAVING imagepng($this-&gt;resource, $destination, 100); // SHOWING header('Content-type: image/png'); imagepng($this-&gt;resource); </code></pre> <p><br> The reason I also save the image is for caching. If the script is executed on a png, it saves a cached png.<br> Next time the image is requested, the png file will be shown, but it has lost its transparency.</p> <p>Even stranger:</p> <ul> <li>When I save that cached png image as (within Firefox), it saves it suddenly as a jpg, even though the extension was png.</li> <li>Downloading the cached png using chrome and opening it in Photoshop gives the error: <code>"file-format module cannot parse the file"</code>.</li> </ul> <p>Once I try to show that saved PNG with the GD library, it gives me an error.</p> <hr> <p><strong>SOLUTION</strong></p> <p>I found out what the problem was. It was a stupid mistake. The script I provided above were cut out of a class and placed as sequential code, while in real this is not what exactly happened. The save image function:</p> <pre><code>function saveImage($destination,$quality = 90) { $this-&gt;loadResource(); switch($extension){ default: case 'JPG': case 'jpg': imagejpeg($this-&gt;resource, $destination, $quality); break; case 'gif': imagegif($this-&gt;resource, $destination); break; case 'png': imagepng($this-&gt;resource, $destination); break; case 'gd2': imagegd2($this-&gt;resource, $destination); break; } } </code></pre> <p>However... $extension does not exist. I fixed it by adding:</p> <pre><code>$extension = $this-&gt;getExtension($destination); </code></pre>
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    1. USHarry Stroker
    1. USHarry Stroker
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      1. VTUpMod
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    1. COYou'd be better off simply doing `readfile($destination)` instead of making your server do the PNG compression routines twice.
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      1. USMarc B
    2. COThanks for your answer. That is not the problem here. The saved PNG does not have a transparency layer and can't be opened in photoshop for instance. I added a link in my post to show what I mean. I hope this makes it clearer... How do I reopen my question? It is not a duplicate..
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      1. USHarry Stroker
    3. COYes you're right this is isn't a duplicate so...I can re-open this provided that you move your solution into a self answer. Also mention at the start of this question that you reviewed the supposed dupe and explain as you did why it doesn't apply. Then flag for a mod to re-open.
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      1. USKev
 

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