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playground:playground [2017/12/19 00:11] executive [Amis linguistes] |
playground:playground [2018/01/06 16:23] (current) plg move metadata to user_documentation:metadata |
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| - | ==== What's all this Metadata stuff, anyway? ==== | ||
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| - | Metadata is information about information. An example would be the album and artist information contained in the ID3 tag of an MP3 song file. In the case of image files, this includes things such as height and width, as well as EXIF and IPTC blocks, which are written to a file when a digital camera takes a photo. Also, additional metadata can be written to the image file later in software, such as keywords. Metadata can be useful to the software you use, as well as to humans. Images may contain both EXIF and IPTC tags. Metadata can be used with many different types of file formats(JPEG, TIFF, RAW etc.). The future of metadata probably lies with the [[https://en.wikipedia.org/wiki/Metadata_Working_Group|Metadata Working Group]] | ||
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| - | === Basic metadata === | ||
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| - | Basic metadata are things like filesize, width/height, color depth and sometimes even thumbnails. All images must have this data, and it is needed by browsers and other software to display the image properly. Historically, this data wasn't considered to be metadata, but in reality it is. | ||
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| - | === EXIF === | ||
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| - | [[https://en.wikipedia.org/wiki/Exif|EXIF]] (Exchangeable image file format) tags are typically used to **describe how a photo was captured**. The standard was created by a consortium of Japanese hardware manufacturers. For example, tags can contain information about the model of camera/smartphone used, lens, aperature size, focal length, exposure duration, date/time, GPS coordinates, etc. It could also contain scanner properties. There are //many// fields defined by the EXIF specification, but the ones used in a particular file will vary by the device used. Since it is an open standard, tag usage should be consistent across various software. | ||
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| - | === IPTC === | ||
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| - | [[https://iptc.org/standards/photo-metadata/iptc-standard/|IPTC]] headers are described by the Information Interchange Model (IIM). The header is named after the International Press Telecommunications Council (based in London), who created the standard in the 1990's to make it easier for news agencies to exchange information using computers. Adobe helped to bring this standard to public use. For our images, the IIM serves a purpose different from EXIF; It **describes the content of the photo**. Some cameras will allow you to record your name, and other copyright information to a digital photo, using this header. Sometimes, editing software is used to later add information like titles. headlines, captions, descriptions, keywords etc. Again, there are many possible fields described in the standard, and they are readable by most programs. | ||
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| - | === MakerNotes === | ||
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| - | IPTC and EXIF are open standards, but hardware manufacturers have their own secret sauce as well. Cameras will often record some metadata to digital photos which is proprietary, and sometimes device specific. Sometimes it is used by the cameras themselves, and sometimes by image processing software distributed by the companies with their cameras. For example, the Makernotes may include points on an image that the camera used for autofocusing, shutter sync, or noise reduction data. Since this metadata may reveal how a particular device works internally, companies do not publish the specifications to protect their business. Despite this, many Makernotes have been [[http://www.exiv2.org/makernote.html|reverse engineered]]. | ||
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| - | === How Piwigo Handles Metadata === | ||
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| - | Piwigo has many ways to display and use metadata. Since metadata is stored with each image, it remains intact even if something happens to you Piwigo database. | ||
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| - | == "Out of the Box" == | ||
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| - | By default, Piwigo displays some basic metadata in the properties list. | ||