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.

Also according to the PNG specification, there is no restriction on the location of text-type chunks (tEXt, zTXt and iTXt). However, certain utilities (including some Apple and Adobe utilities) won't read the XMP iTXt chunk if it comes after the IDAT chunk, and at least one utility won't read other text chunks here. For this reason, when writing, ExifTool 11.63 and later create new text chunks (including XMP) before IDAT, and move existing text chunks to before IDAT.

The PNG format contains CRC checksums that are validated when reading with either the Verbose or Validate option. When writing, these checksums are validated by default, but the FastScan option may be used to bypass this check if speed is more of a concern.

Tag ID Tag Name Writable Values / Notes

'IHDR' ImageHeader - --> PNG ImageHeader Tags

'PLTE' Palette no

'acTL' AnimationControl - --> PNG AnimationControl Tags

'bKGD' BackgroundColor no

'cHRM' PrimaryChromaticities - --> PNG PrimaryChromaticities Tags

'cICP' CICodePoints - --> PNG CICodePoints Tags

'caBX' JUMBF - --> Jpeg2000 Tags

'dSIG' DigitalSignature no

'eXIf' eXIf - --> EXIF Tags
(this is where ExifTool will create new EXIF)

'fRAc' FractalParameters no

'gAMA' Gamma yes! (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. When creating a new ICC_Profile, the SRGBRendering tag should be deleted if it exists)

'iCCP-name' ProfileName yes (not a real tag ID, this tag represents the iCCP profile name, and may only be written when the ICC_Profile is written)

'iDOT' AppleDataOffsets no

'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 yes! (this chunk should not be present if an iCCP chunk exists)
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
(a once-proposed chunk for compressed EXIF)

PNG ImageHeader Tags

Index1 Tag Name Writable Values / 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 Control chunk. See https://wiki.mozilla.org/APNG_Specification for details.

Index4 Tag Name Writable Values / Notes

0 AnimationFrames no

1 AnimationPlays no

PNG PrimaryChromaticities Tags

Index4 Tag Name Writable Values / 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 CICodePoints Tags

These tags are found in the PNG cICP chunk and belong to the PNG-cICP family 1 group.

Index1 Tag Name Writable Values / Notes

0 ColorPrimaries no 1 = BT.709
2 = Unspecified
4 = BT.470 System M (historical)
5 = BT.470 System B, G (historical)
6 = BT.601
7 = SMPTE 240
8 = Generic film (color filters using illuminant C)
9 = BT.2020, BT.2100
10 = SMPTE 428 (CIE 1921 XYZ)
11 = SMPTE RP 431-2
12 = SMPTE EG 432-1
22 = EBU Tech. 3213-E

1 TransferCharacteristics no
0 = For future use (0)
1 = BT.709
2 = Unspecified
3 = For future use (3)
4 = BT.470 System M (historical)
5 = BT.470 System B, G (historical)
6 = BT.601
7 = SMPTE 240 M
8 = Linear
9 = Logarithmic (100 : 1 range)
10 = Logarithmic (100 * Sqrt(10) : 1 range)
11 = IEC 61966-2-4
12 = BT.1361
13 = sRGB or sYCC
14 = BT.2020 10-bit systems
15 = BT.2020 12-bit systems
16 = SMPTE ST 2084, ITU BT.2100 PQ
17 = SMPTE ST 428
18 = BT.2100 HLG, ARIB STD-B67

2 MatrixCoefficients no 0 = Identity matrix
1 = BT.709
2 = Unspecified
3 = For future use (3)
4 = US FCC 73.628
5 = BT.470 System B, G (historical)
6 = BT.601
7 = SMPTE 240 M
8 = YCgCo
9 = BT.2020 non-constant luminance, BT.2100 YCbCr
10 = BT.2020 constant luminance
11 = SMPTE ST 2085 YDzDx
12 = Chromaticity-derived non-constant luminance
13 = Chromaticity-derived constant luminance
14 = BT.2100 ICtCp

3 VideoFullRangeFlag 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. User-defined tags may set an 'iTXt' flag in the tag definition to be written only as 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 ID Tag Name Writable Values / Notes

'Artist' Artist string (unregistered)

'Author' Author string

'Collection' Collection string

'Comment' Comment string

'Copyright' Copyright string

'Creation Time' CreationTime string (stored in RFC-1123 format and converted to/from EXIF format by ExifTool)

'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.

Index1 Tag Name Writable Values / Notes

0 PixelsPerUnitX int32u (default 2834)

4 PixelsPerUnitY int32u (default 2834)

8 PixelUnits int8u (default meters)
0 = Unknown
1 = meters

PNG SubjectScale Tags

Index1 Tag Name Writable Values / Notes

0 SubjectUnits no 1 = meters
2 = radians

1 SubjectPixelWidth no

2 SubjectPixelHeight no

PNG StereoImage Tags

Index1 Tag Name Writable Values / Notes

0 StereoMode no 0 = Cross-fuse Layout
1 = Diverging-fuse Layout

PNG VirtualPage Tags

Index4 Tag Name Writable Values / Notes

0 VirtualImageWidth no

1 VirtualImageHeight no

2 VirtualPageUnits no

(This document generated automatically by Image::ExifTool::BuildTagLookup)
Last revised Feb 9, 2023

<-- ExifTool Tag Names