php support for WEBP image metadata

Question

Does php support webp image metadata?

Specifically, I want to be able to read and write XMP and EXIF metadata for webp images natively in php code.

I have been experimenting with the below code and it is giving me a "File not supported in" warning.

<?php

$photoSourceThumbnail = "publicAssets/images/att_galleryWebP/A0001_LSF-PHOTOS-WM-TM-WEBP/A0001-EWF-LSF-01.webp";
$photoSourceFull = "assets/images/att_galleryWebP/A0001_LSF-PHOTOS-WM-FULL-WEBP/A0001-EWF-LSF-01.webp";

echo "$photoSourceFull:<br />\n";
$exif = exif_read_data($photoSourceFull, 'IFD0');
echo $exif===false ? "No header data found.<br />\n" : "Image contains headers<br />\n";

$exif = exif_read_data($photoSourceFull, 0, true);
echo "test2.jpg:<br />\n";
foreach ($exif as $key => $section) {
    foreach ($section as $name => $val) {
        echo "$key.$name: $val<br />\n";
    }
}

So far my website has 6000 images which I converted from jpg to webp using this online tool. https://nsspot.herokuapp.com/imagetowebp/. — Elliott Farmer, Nov 24 '21 at 18:22
With 6000 pictures I expected you to be more interested in answers to your Q... — AmigoJack, Dec 28 '21 at 19:08

score 1 · Accepted Answer · edited Dec 09 '21 at 07:53

1

It is better to use ExifTool for this.

Install ExifTool

https://exiftool.org/

PHP example

class ExifToolException extends RuntimeException{}

function getInfo(string $file) : object 
{
    $info = shell_exec('exiftool -json ' . escapeshellarg($file) . ' 2>&1');
    if(strpos($info, 'Error:') > -1) {
        throw new ExifToolException(rtrim($info, PHP_EOL));
    }
    return json_decode($info)[0];
}

try {
    var_dump(getInfo('abc.webp')->Megapixels);
} catch(ExifToolException $e) {
    var_dump($e->getMessage());
}

Update: ExifTool does not support writing webp

Instead you can look at webpmux from Google: https://developers.google.com/speed/webp/docs/webpmux

edited Dec 09 '21 at 07:53

Walf

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answered Nov 24 '21 at 17:36

Douma

2,682
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Thx for feedback about webpmux. – Elliott Farmer Jan 03 '22 at 17:11
@Douma do you have an example on how to use the webpmux? I find their example too vague. – Gellie Ann Feb 02 '22 at 05:10

AmigoJack · Answer 2 · 2021-12-05T14:43:28.550

WebP supports both Exif and XMP for years already. The format is based on RIFF and acknowledges at least the chunks EXIF, XMP and ICCP. Good software will also read an IPTC chunk.

Just because some random software does not consider carrying over metadata doesn't mean the target format doesn't support it - most software is rather sloppy than ambitious. Since the RIFFormat is rather trivial it should be easy to modify existing files to include more chunks:

Each chunk consists of 4 bytes identifier/FourCC (i.e. the ASCII characters EXIF), then 4 bytes of its size in little Endian, then the payload.
The file's first chunk is similar: it starts with the 4 bytes RIFF, then 4 bytes of its entire filesize minus 8, then 4 bytes of content identification, here WEBP (to distinguish this from other formats also using RIFF, such as WAV, AVI, Maya, AIF, MIDI...).
This means you append your new chunk at the end of the file and then patch bytes 5 through 8 of the file with the new filesize. Example:

$sExif= '...the binary data...';  // You read that off the other file, of course
$iLenExif= strlen( $sExif );  // Payload length in bytes
if( $iLenExif% 2== 1 ) $sExif.= "\0";  // RIFF needs 16bit alignment

$hFile= fopen( 'TARGET.WEBP', 'r+' );   // Read and write access
fseek( $hFile, 0, SEEK_END );  // Go to end of file

fwrite( $hFile, 'EXIF' );  // 4 bytes chunk ID
fwrite( $hFile, pack( 'V', $iLenExif ) );  // 4 bytes of payload length
fwrite( $hFile, $sExif );  // Actual data

$iFilesize= ftell( $hFile );  // Should be bigger
fseek( $hFile, 4, SEEK_SET );  // Go to 5th byte of file
fwrite( $hFile, pack( 'V', $iFilesize- 8 ) );  // Write 4 bytes, patching old filesize

fclose( $hFile );  // Store everything.

Elliott Farmer · Answer 3 · 2022-01-11T02:18:20.790

Google have recently changed the image requirements for web sites saying that they should include IPTC image rights metadata.

https://developers.google.com/search/docs/advanced/appearance/image-rights-metadata

I have successfully been able to update image XMP,EXIF and IPTC metadata for a jpg image from my SQL table using EXIFTOOL to meet these new google requirements. I have checked the test image on the IPTC tool and it does contain the desired XMP,EXIF and IPTC metadata.

https://getpmd.iptc.org/getiptcpmd.html

However.........

Extensive reading into the WEBP format and tools such as exiv2, dwebp and webpmux, can only write XMP and EXIF metadata to a webp image.

https://www.exiv2.org/manpage.html
https://developers.google.com/speed/webp/docs/cwebp
https://developers.google.com/speed/webp/docs/webpmux
https://image.online-convert.com/convert-to-webp (drag and drop web tool that converts Jpg to webp with XMP & Exif metadata)

It would seem that webp DOES NOT SUPPORT IPTC metadata therefore does not fulfil these requirements:

https://developers.google.com/search/docs/advanced/appearance/image-rights-metadata

Conclusions:

Webp as an image format for images that I want google indexed, is a dead duck unless/until google modify the RIFF header to include IPTC.
Next steps are to revert images on my website back to jpg.

For anyone interested in how I modified the image XMP,EXIF and IPTC metadata from php.

a) These are the metadata fields that I finally decided upon with the exiftool commands to update them.

exiftool -iptc:by-line="image creator" A0000-01.jpg
exiftool -xmp:creator="image creator" A0000-01.jpg
exiftool -exif:Artist="image creator" A0000-01.jpg

exiftool -iptc:CopyrightNotice="Copywrite 2022 websiteName.com" A0000-01.jpg
exiftool -xmp:rights="Copywrite 2022 websiteName.com" A0000-01.jpg
exiftool -exif:Copyright="Copywrite 2022 websiteName.com" A0000-01.jpg

exiftool -iptc:keywords="keyword1,keyword2,keyword3" A0000-01.jpg
exiftool -xmp:Subject="keyword1,keyword2,keyword3" A0000-01.jpg
exiftool -exif:UserComment="keyword1,keyword2,keyword3" A0000-01.jpg

exiftool -iptc:credit="image reproduced with permission from" A0000-01.jpg
exiftool -xmp:credit="image reproduced with permission from" A0000-01.jpg

exiftool -iptc:ObjectName="Image title" A0000-01.jpg
exiftool -xmp:Title="Image title" A0000-01.jpg

exiftool -iptc:Caption-Abstract="Image description" A0000-01.jpg
exiftool -xmp:description="Image description" A0000-01.jpg
exiftool -exif:ImageDescription="Image description" A0000-01.jpg

exiftool -iptc:Source="Url where image can be found" A0000-01.jpg
exiftool -xmp:Source="Url where image can be found" A0000-01.jpg

exiftool -exif:gpslatitude="44.081102" -exif:gpslatituderef=N A0000-01.jpg
exiftool -exif:gpslongitude="-35.489600" -exif:gpslongituderef=W A0000-01.jpg
exiftool -xmp:gpslatitude="44.081102 N" A0000-01.jpg
exiftool -gpslongitude="-35.489600 E" A0000-01.jpg

exiftool -xmp:AuthorsPosition="website owner & coder" A0000-01.jpg
exiftool -iptc:By-lineTitle="website owner & coder" A0000-01.jpg

exiftool -xmp:CaptionWriter="websiteName.com.com" A0000-01.jpg
exiftool -iptc:Writer-Editor="websiteName.com.com" A0000-01.jpg

b) In php I am using the below code to generate a string of text that contains the exiftoolcommand:

$F_XmpDescriptionSt = 'exiftool -xmp:description="'.$iptcDescription.'" "'.$absoluteImgJpgFullSizePath.'"';

where $iptcDescription and $absoluteImgJpgFullSizePath are the desired metadata values from mySQL table

c) I am then launching the command via command prompt terminal with below code:

$FullsizeExiftoolXmpDescriptionExecute = exec("$F_XmpDescriptionSt");

I repeat the above for all of the metadata fields I want to update, adjusting the php code to the exiftool command.

I am sure there is a more elegant way of doing this such as a batch script?? but I prefer to launch each exiftool command as a single line of code one by one so that I get the response message "1 files updated" for each metadata field that I update. It takes about 15 seconds to complete the code for all metadata fields so not a big issue.

This line of code outputs the exiftool response contained in variable FullsizeExiftoolXmpDescriptionExecute.

<h4>Fullsize XMP Description $FullsizeExiftoolXmpDescriptionExecute to $iptcDescription</h4>

This video tutorial explains how to install exiftool on windows 10. https://www.youtube.com/watch?v=Ku1Nx-kl7RM

According to your first link, at the time of this writing, Google recommends adding IPTC fields, not that they require it... or perhaps I'm just missing something? — Gellie Ann, Feb 02 '22 at 23:22
You ignored my answer, which even states by chance IPTC. But what makes this answer a mess is that your question never mentioned IPTC which now is mandatory to you. On top nothing in here is PHP - it's just starting external programs. — AmigoJack, Feb 03 '22 at 01:21
Hello Gellie Ann. The subject of image metadata is very vague especially on google developer support. The solution that I used in the end was to add the IPTC tags in the XMP format and where possible the EXIF format using exiftool then convert the images to webp using cwebp. WebP does not natively support IPTC tags nor have I found any tools that could generate an IPTC tag. I have asked about future IPTC tag support with the cwebp development team. I in no way present this as the correct solution but as the method I used for anyone else reading about image metatags. — Elliott Farmer, Feb 03 '22 at 10:05
AmigoJack thanks for your input which I did not ignore but was included in my overall research into image metadata. The question is about PHP support for webp image metadata PHP cannot natively read nor write image metadata for webp with the existing inbuilt functions. PHP has read only support for XMP and EXIF with read write capability for IPTC. Because of the limited support for image metadata in php I feel that the inclusion of use of external programs is relevant. — Elliott Farmer, Feb 03 '22 at 10:26
@ElliottFarmer Will the metadata from the file you have converted still be available on the webp file? Did it get converted as well? — Gellie Ann, Feb 04 '22 at 01:37
Gellie Ann - Yes! the webp files have XMP and EXIF metadata. I am checking them in GIMP. I used libwebp-1.2.1-windows-x64-no-wic.zip to convert them. other versions of cwebp did not work for me. — Elliott Farmer, Feb 04 '22 at 11:33

php support for WEBP image metadata

3 Answers3

Install ExifTool

PHP example

Update: ExifTool does not support writing webp