Ultimately, because the PNG specification did not enforce more metadata tags than it did, authors of PNG software had no guarantee that tags such as "Author" would be parsed and read by other PNG implementations. This was done so that existing PNG implementations written before the introduction of the iTXt chunk could read the chunk headers and keywords, and skip over text they couldn't parse, read, or render. The iTXt chunk was eventually added, that uses the Unicode character set, sort of: the keywords in the iTXt chunks are encoded in Latin-1 character set the values in the chunks are Unicode. Thus, the tEXt chunks use the Latin-1 (ISO/IEC 8859-1) character set. Because the designers of PNG wanted to rely on stable, tested technologies when they authored the PNG specification, they made the reasonable decision to not use it. But as implemented in the 1990's, the PNG specification is not sufficient to write robust software that uses, reads, or relies on more metadata than you're seeing.Īlso from the same link to above, "Unicode UTF-8 character set was one of the items in the design of PNG that was voted down." UTF-8 was not well supported by any of the major system libraries and operating systems at the time.
Thus, the authors of the PNG specification intended a loose, flexible way of embedding all sorts of information. If the original image were a painting or other nonelectronic medium, both the original artist and the person who scanned the image might be listed. From the link to above,Īuthor The name of the author of the image.
#XNVIEWMP ADD TEXT WINDOWS#
Even if you embed an "Author" key in the text chunk(s), there's no guarantee a standard Windows user will be able to see it.Įdit: Additionally, multiple chunks can exist, using the same keyword(s) again. The Windows built-in shell extension that displays image information does not fully support "Author" keywords in tEXt/ zTXt chunks. "Author" is a reserved keyword for tEXt/ zTXt chunks, but PNG readers are not required to respect reserved keywords for those chunks. Photo.SE: How do I go about editing the metadata of a PNG file?.Superuser: What software can I use to read png metadata?.There are several applications and software libraries that can read and write embedded text chunks, including on Windows:
StackOverflow: Does PNG contain EXIF data like JPG?.PNG file, and is it possible to copy “Date Modified” to “Date Taken”? Photo.SE: Is “Date Taken” Exif data possible on.While PNG can embed metadata chunks, standard metadata formats such as EXIF, IPTC, or XMP are not supported for PNG. TL DR: PNG doesn't formerly didn't support EXIF metadata (when the question was asked) See comments by posfan12 and lukeuser below. exiftool can edit PNG chunks, but Windows explorer apparently still does not support PNG chunks. As of July 2017, PNG supports EXIF chunks.
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