Unable to strip metadata with keep

[hugopeek]

Hi! Thanks, first of all, for this amazing library. It saved my ass when the Squoosh project was (rather quietly) abandoned.

I'm using PHP now to resize the images, and for web-facing thumbnails I'm trying to remove the EXIF data.. But I'm having some difficulties figuring it out.

$image = Vips\Image::thumbnail($srcPath, $width, ['height' => $height]);
$image
    ->jpegsave($tempFile, [
        'Q' => $quality,
        'keep' => ['none'],
    ]
);

It seems to be expecting an array, but whatever I feed it: nothing gets stripped.

I did stumble upon the 'strip' property just now, and that takes care of it, albeit bluntly. What am I missing that I can't use the more selective 'keep' method? I tried using the 2 in conjuction, but that only seems to bypass strip altogether.

[hugopeek]

Hmm. Without the array, it does strip metadata.. But it always seems to be all of it, regardless of using 'keep' => 'all' or a similar setting.

[jcupitt]

Hi @hugopeek, we added flag parsing to the string -> enum converter to avoid having to change any of the language bindings. Try 'keep' => 'exif|icc'.

[jcupitt]

I made a test program:

require dirname(__DIR__) . '/vendor/autoload.php';

use Jcupitt\Vips;

function printMetadata($im) {
    foreach ($im->getFields() as &$name) {
        $value = $im->get($name);
        if (str_ends_with($name, "-data")) { 
            $len = strlen($value);
            $value = "<$len bytes of binary data>";
        }
        echo "   $name: $value\n";
    }
}

$im = Vips\Image::newFromFile($argv[1]);
echo "$argv[1]\n";
printMetadata($im);

$buf = $im->tiffsave_buffer(['keep' => 'icc']);
$im2 = Vips\Image::newFromBuffer($buf, "");
echo "\nafter keep => icc\n";
printMetadata($im2);

$buf = $im->tiffsave_buffer(['keep' => 'exif:icc']);
$im2 = Vips\Image::newFromBuffer($buf, "");
echo "\nafter keep => exif:icc\n";
printMetadata($im2);

But it doesn't seem to work! I'll investigate.

[jcupitt]

There are some changes needed for php-vips to support symbolic flag values, I'll make a PR.

In the meantime, you can always pass an int, for example:

abstract class ForeignKeep
{
    const NONE = 0;
    const EXIF = 1;
    const XMP = 2;
    const IPTC = 4;
    const ICC = 8;
    const OTHER = 16;
    const ALL = 31;
}

$buf = $im->tiffsave_buffer(['keep' => ForeignKeep.EXIF | ForeignKeep.ICC]);

[hugopeek]

Hi @jcupitt, thanks for the swift reply!

Ah, so it's an enum.. That's still relatively new for us PHP folk :) Using the int numbers seems to work without issue in my own code, but not in your example. Anyway, thanks a bunch for the quick workaround!

[jcupitt]

It should be fixed in master, and I added an example:

https://github.com/libvips/php-vips/blob/master/examples/keep.php

Thanks for reporting this!