Compress PNG files in PHP

Question

I am generating PNG file with cairo extension of PHP. The image contains a background and a text. Now I want to compress these images by PHP after its generated by cairo. Is there any library to do this?

I found pngcrush tool. But its a command line tool. I dont want to invoke system call. If there is not PHP solution a C solution would do. In that case I'll make a PHP extension.

I have read this related question. But there is no answer in it.

score 3 · Answer 1 · answered Mar 30 '12 at 17:47

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You can use imagepng() ...

//If you don't already have a handle to the image and it's just on the file system...
$im = imagecreatefrompng("yourGenerateFile.png");
$quality = 5; //0 - 9 (0= no compression, 9 = high compression)
imagepng($im, 'file/to/save.png', $quality);  //leave out filename if you want it to output to the buffer
imagedestroy($im);

answered Mar 30 '12 at 17:47

Brad Harris

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I have already a cairo handle but not a gd handle. I'll try your code and let you know. – Shiplu Mokaddim Mar 30 '12 at 17:55
The quality is not preserved. Transparency lost completely! – Shiplu Mokaddim Mar 30 '12 at 18:09
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For transparency use : `imageAlphaBlending($im, true); imageSaveAlpha($im, true);` like said here : http://php.net/manual/en/function.imagecreatefrompng.php#43024 – Nicolas Boisteault Jul 28 '16 at 15:15

score 1 · Accepted Answer · answered Mar 30 '12 at 19:48

I would take a look at PngOptimizer. You can get the source for it at the bottom of the page, and it has a separated CLI version too.

Only problem is that source is C++ , not ANSI C. I have never made a PHP extension, so i don't know if it makes a difference.

score 0 · Answer 3 · answered Mar 30 '12 at 17:43

0

For C code take a look at ImageMagick. It looks like there is a PHP extension too.

answered Mar 30 '12 at 17:43

RunHolt

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Read http://stackoverflow.com/questions/7462827/phpimagick-png-compression it does not work that way. – Shiplu Mokaddim Mar 30 '12 at 17:45
Aha! It looks like a PHP problem not an ImageMagick issue. You could either add the flag to the PHP-ImageMagick extension or create your own. [MagickCore](http://www.imagemagick.org/script/magick-core.php) has an example (search for 'example') of how to convert a gif to a png in code. – RunHolt Mar 30 '12 at 17:54
If you see the related question, there OP tried it with PHP but I tried in command line too. in both case I achieve no more than 10% compression. – Shiplu Mokaddim Mar 31 '12 at 03:16

Compress PNG files in PHP

3 Answers3