How to get rid of png exif metadata?

[Marsu42]

After some jpg->png concersion with ImageMagick and exiftool, I end up with png images containing copies of the jpeg exif metadata. The problem is that currently I cannot find any way to get rid of these tags. Here's a sample output of exiftool -S -G1 -sort -a -e -n

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[ExifTool] ExifToolVersion: 9.67
[System] Directory: .
[System] FileAccessDate: 2014:10:08 18:32:39+02:00
[System] FileCreateDate: 2014:10:08 18:32:41+02:00
[System] FileModifyDate: 2014:08:15 12:59:33+02:00
[System] FileName: FAU_L_EF96AA73_576x_WEB.png
[System] FilePermissions: 666
[System] FileSize: 343509
[File] ExifByteOrder: MM
[File] FileType: PNG
[File] MIMEType: image/png
[PNG] BackgroundColor: 255 255 255
[PNG] BitDepth: 8
[PNG] ColorType: 6
[PNG] Compression: 0
[PNG] Filter: 0
[PNG] ImageHeight: 384
[PNG] ImageWidth: 576
[PNG] Interlace: 0
[PNG] PixelUnits: 1
[PNG] PixelsPerUnitX: 2834
[PNG] PixelsPerUnitY: 2834
[PNG] ProfileName: icm
[PNG] SRGBRendering: 0
[PNG] datecreate: 2014-10-08T18:09:24+02:00
[PNG] datemodify: 2014-08-15T12:59:33+02:00
[PNG] exifApertureValue: 7400879/1000000
[PNG] exifColorSpace: 1
[PNG] exifCompression: 6
[PNG] exifCustomRendered: 0
[PNG] exifDateTime: 2014:08:14 23:10:35
[PNG] exifDateTimeDigitized: 2014:08:08 12:28:54
[PNG] exifDateTimeOriginal: 2014:08:08 12:28:54
[PNG] exifExifOffset: 350
[PNG] exifExifVersion: 48, 50, 51, 48
[PNG] exifExposureBiasValue: 0/1
[PNG] exifExposureMode: 1
[PNG] exifExposureProgram: 1
[PNG] exifExposureTime: 1/250
[PNG] exifFNumber: 13/1
[PNG] exifFlash: 9
[PNG] exifFocalLength: 100/1
[PNG] exifFocalPlaneResolutionUnit: 2
[PNG] exifFocalPlaneXResolution: 1036800/181
[PNG] exifFocalPlaneYResolution: 691200/119
[PNG] exifGPSInfo: 912


... and so on. Any ideas on how to access these [PNG] tags? I tried -PNG:all= which does nothing and -PNG:exifWhatever= doesn't work either, or I made some stupid mistake somewere along the way.

[Phil Harvey]

These sound like PNG TextualData tags.  The PNG tag documentation explains this.

- Phil

[Marsu42]

The PNG tag documentation explains this.

Excuse me being very slow, but as far as I understand the link it explains why I *cannot* get rid of the png tags (unless I add each and every one to my config file)? If so, probably at least a working -PNG:all= in exiftool would be nice that gets rid of everything except the core 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.

On an unrelated note and just out of interest: What's the big deal with exiftool just being able to delete every PNG TextualData I want right away w/o whitelisting them in the config file?

[Phil Harvey]

Good point.  I'll implement this in ExifTool 9.73.

- Phil