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[RESOLVED] imagecreatefromjpeg ruins quality of images

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May 22.2010

Hello,

I’ve been using imagecreatefromjpeg to regenerate an existing image. However, I do not want the quality to be changed during this process.

This is what I currently have:

[code=php]
$imagepath = http://site.com/path/to/image.jpg;
$image = imagecreatefromjpeg($imagepath);
header(‘Content-Type: image/jpeg’);
imagejpeg($image);
[/code]

Which, as you can see, is a basic use of imagecreatefromjpeg. However, the quality is greatly diminished after this process. Is there a way to keep the quality at the same level as the original (100%)? Or is there an alternative function I can use on existing images, not to resize or anything?

I’ve been googling for hours over this and haven’t been able to find any solid answers, except a hint that “imagejpeg” might be a possibility, but from what I’ve found it’s not for existing images…?

I would really appreciate any help I can get.
Thanks!

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PHP

6 Comments(s) ↴

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@aj_nscMay 22.2010 — imagejpeg($image,$imagepath,100)

Default for the third parameter (quality) is approx. 75, according to php.net:

http://ca2.php.net/imagejpeg

By changing it to 100, you should get a higher quality.
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@boxofmochiauthorMay 22.2010 — Thank you so much for your response!

Actually I tried that code, and found it worked when I changed $imagepath to NULL:
[code=php]
$imagepath = http://site.com/path/to/image.jpg;
$image = imagecreatefromjpeg($imagepath);
header('Content-Type: image/jpeg');
imagejpeg($image, NULL, 100);
[/code]

However, the odd thing is that now the script is [I]increasing[/I] my image sizes even though the original files were optimized at smaller filesizes.

Ex: image.jpg is originally at 125kb, but after running through the script it becomes 600kb.

How is this possible?
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@boxofmochiauthorMay 24.2010 — Filesize is not necessarily proportional to Quality of the file ?.

Thanks for all your help!
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@tirnaMay 24.2010 — In Photoshop, and I assume other applications, the quaility property refers to how much jpeg compression you want to apply to the saved or created output image.

0% quality means maximum compression and 100% quality means minimum compression.

The more compression you apply, the smaller the output filesize will be relative to the original uncompressed filesize.
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@boxofmochiauthorMay 24.2010 — Right, but the thread refers to compression by php code outputting an image.
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@tirnaMay 24.2010 — But does the php function use the same or similar jpeg compression algorithm as Photoshop does? [B]I don't know.[/B]

The point I was making is that filesize (in at least Photoshop) is related to the 'quality/compression' you choose when saving a jpeg file.
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