PNG Tags

Tags extracted from PNG images. See http://www.libpng.org/pub/png/spec/1.2/ for the official PNG 1.2 specification.

According to the specification, a PNG file should end at the IEND chunk, however ExifTool will preserve any data found after this when writing unless it is specifically deleted with -Trailer:All=. When reading, a minor warning is issued if this trailer exists, and ExifTool will attempt to parse this data as additional PNG chunks.

Tag IDTag Name WritableValues / Notes
'IHDR' ImageHeader - --> PNG ImageHeader Tags
'PLTE' Palette no  
'acTL' AnimationControl - --> PNG AnimationControl Tags
'bKGD' BackgroundColor no  
'cHRM' PrimaryChromaticities - --> PNG PrimaryChromaticities Tags
'dSIG' DigitalSignature no  
'exIf' exIf - --> EXIF Tags
(proposed but not yet registered. This is where ExifTool will create new EXIF without the Compress option)
'fRAc' FractalParameters no  
'gAMA' Gamma no (ExifTool reports the gamma for decoding the image, which is consistent with the EXIF convention, but is the inverse of the stored encoding gamma)
'gIFg' GIFGraphicControlExtension no  
'gIFt' GIFPlainTextExtension no  
'gIFx' GIFApplicationExtension no  
'hIST' PaletteHistogram no  
'iCCP' ICC_Profile - --> ICC_Profile Tags
(this is where ExifTool will write a new ICC_Profile)
'iCCP-name' ProfileName no (not a real tag ID, this tag represents the iCCP profile name)
'iTXt' InternationalText - --> PNG TextualData Tags
'oFFs' ImageOffset no  
'pCAL' PixelCalibration no  
'pHYs' PhysicalPixel - --> PNG PhysicalPixel Tags
'sBIT' SignificantBits no  
'sCAL' SubjectScale - --> PNG SubjectScale Tags
'sPLT' SuggestedPalette no  
'sRGB' SRGBRendering no 0 = Perceptual
1 = Relative Colorimetric
2 = Saturation
3 = Absolute Colorimetric
'sTER' StereoImage - --> PNG StereoImage Tags
'tEXt' TextualData - --> PNG TextualData Tags
'tIME' ModifyDate yes  
'tRNS' Transparency no  
'tXMP' XMP - --> XMP Tags
(obsolete location specified by a September 2001 XMP draft)
'vpAg' VirtualPage - --> PNG VirtualPage Tags
'zTXt' CompressedText - --> PNG TextualData Tags
'zxIf' zxIf - --> EXIF Tags
(proposed but not yet registered. This is where ExifTool will create new EXIF with the Compress option)

PNG ImageHeader Tags

Index1Tag Name WritableValues / Notes
0 ImageWidth no  
4 ImageHeight no  
8 BitDepth no  
9 ColorType no 0 = Grayscale
2 = RGB
3 = Palette
4 = Grayscale with Alpha
6 = RGB with Alpha
10 Compression no 0 = Deflate/Inflate
11 Filter no 0 = Adaptive
12 Interlace no 0 = Noninterlaced
1 = Adam7 Interlace

PNG AnimationControl Tags

Tags found in the Animation Conrol chunk. See https://wiki.mozilla.org/APNG_Specification for details.

Index4Tag Name WritableValues / Notes
0 AnimationFrames no  
1 AnimationPlays no  

PNG PrimaryChromaticities Tags

Index4Tag Name WritableValues / Notes
0 WhitePointX no  
1 WhitePointY no  
2 RedX no  
3 RedY no  
4 GreenX no  
5 GreenY no  
6 BlueX no  
7 BlueY no  

PNG TextualData Tags

The PNG TextualData format allows arbitrary tag names to be used. The tags listed below are the only ones that can be written (unless new user-defined tags are added via the configuration file), however ExifTool will extract any other TextualData tags that are found. All TextualData tags (including tags not listed below) are removed when deleting all PNG tags.

These tags may be stored as tEXt, zTXt or iTXt chunks in the PNG image. By default ExifTool writes new string-value tags as as uncompressed tEXt, or compressed zTXt if the Compress (-z) option is used and Compress::Zlib is available. Alternate language tags and values containing special characters (unless the Latin character set is used) are written as iTXt, and compressed if the Compress option is used and Compress::Zlib is available. Raw profile information is always created as compressed zTXt if Compress::Zlib is available, or tEXt otherwise. Standard XMP is written as uncompressed iTXt.

Alternate languages are accessed by suffixing the tag name with a '-', followed by an RFC 3066 language code (eg. "PNG:Comment-fr", or "Title-en-US"). See http://www.ietf.org/rfc/rfc3066.txt for the RFC 3066 specification.

Some of the tags below are not registered as part of the PNG specification, but are included here because they are generated by other software such as ImageMagick.

Tag IDTag Name WritableValues / Notes
'Artist' Artist string (unregistered)
'Author' Author string  
'Comment' Comment string  
'Copyright' Copyright string  
'Creation Time' CreationTime string  
'Description' Description string  
'Disclaimer' Disclaimer string  
'Document' Document string (unregistered)
'Label' Label string (unregistered)
'Make' Make string (unregistered)
'Model' Model string (unregistered)
'Raw profile type 8bim' Photoshop_Profile - --> Photoshop Tags
(unregistered)
'Raw profile type APP1' APP1_Profile - --> EXIF Tags
--> XMP Tags
(unregistered)
'Raw profile type exif' EXIF_Profile - --> EXIF Tags
(unregistered)
'Raw profile type icc' ICC_Profile - --> ICC_Profile Tags
(unregistered)
'Raw profile type icm' ICC_Profile - --> ICC_Profile Tags
(unregistered)
'Raw profile type iptc' IPTC_Profile - --> Photoshop Tags
(unregistered. May be either IPTC IIM or Photoshop IRB format. This is where ExifTool will add new IPTC, inside a Photoshop IRB container)
'Raw profile type xmp' XMP_Profile - --> XMP Tags
(unregistered)
'Software' Software string  
'Source' Source string  
'TimeStamp' TimeStamp string (unregistered)
'Title' Title string  
'URL' URL string (unregistered)
'Warning' PNGWarning string  
'XML:com.adobe.xmp' XMP - --> XMP Tags
(unregistered, but this is the location according to the June 2002 or later XMP specification, and is where ExifTool will add a new XMP chunk if the image didn't already contain XMP)
'create-date' CreateDate string (unregistered)
'modify-date' ModDate string (unregistered)

PNG PhysicalPixel Tags

These tags are found in the PNG pHYs chunk and belong to the PNG-pHYs family 1 group. They are all created together with default values if necessary when any of these tags is written, and may only be deleted as a group.

Index1Tag Name WritableValues / Notes
0 PixelsPerUnitX int32u  
4 PixelsPerUnitY int32u  
8 PixelUnits int8u 0 = Unknown
1 = meters

PNG SubjectScale Tags

Index1Tag Name WritableValues / Notes
0 SubjectUnits no 1 = meters
2 = radians
1 SubjectPixelWidth no  
2 SubjectPixelHeight no  

PNG StereoImage Tags

Index1Tag Name WritableValues / Notes
0 StereoMode no 0 = Cross-fuse Layout
1 = Diverging-fuse Layout

PNG VirtualPage Tags

Index4Tag Name WritableValues / Notes
0 VirtualImageWidth no  
1 VirtualImageHeight no  
2 VirtualPageUnits no  

(This document generated automatically by Image::ExifTool::BuildTagLookup)
Last revised Apr 5, 2017

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