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I've recently written a Python module that writes meta tags and values to PNG images using PIL, with the intent to have a webpage read the tags and sort the images accordingly (I'm not interested in the default stuff like Camera Type, I attach tags like "CarModel" if I've just been to a rally for example.

Does anyone recommend a way of reading the PNG meta? I'm using PHP at the moment (http://stackoverflow.com/questions/2190236/how-can-i-read-png-metadata-from-php at the bottom) which is great for the reason that it only pics up the tags I've added, but annoying as I can't figure away of building a neat array with the data for many pictures. Can javascript do this?

Sorry If I've been rubbish at explaining, but I'll re-explain if needs be.

MPelletier
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joedborg
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4 Answers4

2

you should have a look at the following php function - exif_read_data

PS: javascript can't do that as far as I know

Oliver M Grech
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1

i had a similar task. I had to write physical dimensions and additional metadata to PNG files. I have found some solutions and combined it into one small library. png-metadata

it could read and write PNG metadata. it could be used on client and server side. May be it will help somebody.

Here how you can read PNG metadata in the Browser: 

        function loadFileAsBlob(url){
            return new Promise((resolve, reject) => {
                var xhr = new XMLHttpRequest();
                xhr.open('GET', url, true);
                xhr.responseType = 'blob';
                xhr.onload = function(e) {
                    if (this.status === 200) {
                        resolve(this.response);
                        // myBlob is now the blob that the object URL pointed to.
                    }else{
                        reject(this.response);
                    }
                };
                xhr.send();
            })
        };

        const blob = await loadFileAsBlob('1000ppcm.png');
        metadata = readMetadataB(blob);
Denis Ponomarev
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The nihilogic Javascript libraries are indeed very useful for client-side EXIF reading and parsing; but that only applies to JPEG images, as the metadata is supported only in the JPEG and TIFF format (and the TIFF format only supported natively by Safari browser). PNG can include metadata but not in the form of IPTC or EXIF fields as JPEG or TIFF formats allow.

user2780218
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Here is a link to a Javascript library that claims to be able to read image metadata:

http://blog.nihilogic.dk/2008/08/imageinfo-reading-image-metadata-with.html

Spudley
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