## PNG Tags

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

> Tag ID | Tag Name | Writable | Values / Notes
> --- | --- | --- | ---
> 'IHDR' | ImageHeader | - | --> PNG ImageHeader Tags
> 'PLTE' | Palette | N |
> 'bKGD' | BackgroundColor | N |
> 'cHRM' | PrimaryChromaticities | - | --> PNG PrimaryChromaticities Tags
> 'dSIG' | DigitalSignature | N |
> 'fRAc' | FractalParameters | N |
> 'gAMA' | Gamma | N |
> 'gIFg' | GIFGraphicControlExtension | N |
> 'gIFt' | GIFPlainTextExtension | N |
> 'gIFx' | GIFApplicationExtension | N |
> 'hIST' | PaletteHistogram | N |
> 'iCCP' | ICC_Profile | - | --> ICC_Profile Tags
> 'iTXt' | InternationalText | - | --> PNG TextualData Tags
> 'oFFs' | ImageOffset | N |
> 'pCAL' | PixelCalibration | N |
> 'pHYs' | PhysicalPixel | - | --> PNG PhysicalPixel Tags
> 'sBIT' | SignificantBits | N |
> 'sCAL' | SubjectScale | - | --> PNG SubjectScale Tags
> 'sPLT' | SuggestedPalette | N |
> 'sRGB' | SRGBRendering | N | 0 = Perceptual 1 = Relative Colorimetric 2 = Saturation 3 = Absolute Colorimetric
> 'sTER' | StereoImage | - | --> PNG StereoImage Tags
> 'tEXt' | TextualData | - | --> PNG TextualData Tags
> 'tIME' | ModifyDate | Y |
> 'tRNS' | Transparency | N |
> 'tXMP' | XMP | - | --> XMP Tags (obsolete location specified by older XMP draft)
> 'vpAg' | VirtualPage | - | --> PNG VirtualPage Tags
> 'zTXt' | CompressedText | - | --> PNG TextualData Tags

## PNG ImageHeader Tags

> Index | Tag Name | Writable | Values / Notes
> --- | --- | --- | ---
> 0 | ImageWidth | N |
> 4 | ImageHeight | N |
> 8 | BitDepth | N |
> 9 | ColorType | N | 0 = Grayscale 2 = RGB 3 = Palette 4 = Grayscale with Alpha 6 = RGB with Alpha
> 10 | Compression | N | 0 = Deflate/Inflate
> 11 | Filter | N | 0 = Adaptive
> 12 | Interlace | N | 0 = Noninterlaced 1 = Adam7 Interlace

## PNG PrimaryChromaticities Tags

> Index | Tag Name | Writable | Values / Notes
> --- | --- | --- | ---
> 0 | WhitePointX | N |
> 1 | WhitePointY | N |
> 2 | RedX | N |
> 3 | RedY | N |
> 4 | GreenX | N |
> 5 | GreenY | N |
> 6 | BlueX | N |
> 7 | BlueY | N |

## 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.

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 (ie. "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 ID | Tag Name | Writable | Values / 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 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)
> '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 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

> Index | Tag Name | Writable | Values / Notes
> --- | --- | --- | ---
> 0 | PixelsPerUnitX | N |
> 4 | PixelsPerUnitY | N |
> 8 | PixelUnits | N | 0 = Unknown 1 = Meters

## PNG SubjectScale Tags

> Index | Tag Name | Writable | Values / Notes
> --- | --- | --- | ---
> 0 | SubjectUnits | N | 1 = Meters 2 = Radians
> 1 | SubjectPixelWidth | N |
> 2 | SubjectPixelHeight | N |

## PNG StereoImage Tags

> Index | Tag Name | Writable | Values / Notes
> --- | --- | --- | ---
> 0 | StereoMode | N | 0 = Cross-fuse Layout 1 = Diverging-fuse Layout

## PNG VirtualPage Tags

> Index | Tag Name | Writable | Values / Notes
> --- | --- | --- | ---
> 0 | VirtualImageWidth | N |
> 1 | VirtualImageHeight | N |
> 2 | VirtualPageUnits | N |

(This document generated automatically by Image::ExifTool::BuildTagLookup)
Last revised Jul 13, 2010

<-- ExifTool Tag Names