Re: EXIF support in PNG - PngSuite image with EXIF chunk

Glenn Randers-Pehrson <[email protected]> Mon, 30 Jan 2017 21:46:28 -0600
Newsgroups	gmane.comp.graphics.png.general
Message-ID	<CA+PdXctf3_AWpXniZOD0hkJF7pvoBvgBOJGjFTXqBXjL+NB34A@mail.gmail.com>
What's illogical?  As is, the profile survives a conversion to PNG+exIF and
back.  ImageMagick expects the Exif00 to be present, and there might be
trouble if it disappeared unexpectedly.  Maybe it wouldn't, but I haven't
tested what happens in that case.

In ImageMagick/GraphicsMagick, the exIf chunk works.  So does zxIf (read
only).

Glenn

On Mon, Jan 30, 2017 at 9:37 PM, Willem van Schaik <[email protected]>
wrote:

>
> Mmm, tough call ...
>
> Doesn't sound all logical, but maybe with a night sleep?  :-)
>
> Willem
>
>
>
> On 2017-01-30 16:18, Glenn Randers-Pehrson wrote:
> > ImageMagick is reporting correctly.  It needs the "Exif00" so the decoder
> > injects it back in again while reading the chunk.  It's in the *profile*
> > not in
> > the exIf chunk.
> >
> > Glenn
> >
> > On Mon, Jan 30, 2017 at 4:59 PM, Willem van Schaik <[email protected]
> > <mailto:[email protected]>> wrote:
> >
> >
> >     looks pretty OK, however ...
> >
> >     when the exif chunk still started with "Exif\0\0" the length of the
> >     chunk was 984 bytes, but after taking out that header the length is
> now
> >     978 bytes
> >
> >     but ImageMagick does report 984, so either there is something wrong
> with
> >     my file, or IM is reporting wrong
> >
> >     we better figure this out :)
> >
> >     Willem
> >
> >
> >     On 2017-01-30 15:10, Glenn Randers-Pehrson wrote:
> >     > On Mon, Jan 30, 2017 at 4:23 PM, Willem van Schaik <
> [email protected] <mailto:[email protected]>
> >     > <mailto:[email protected] <mailto:[email protected]>>> wrote:
> >     >
> >     >
> >     >     has anybody been able to run these two images through their
> (png
> >     >     reading) software to verify that these contain valid exif
> chunks?
> >     >
> >     >
> >     > Here's the output of ImageMagick's "identify -verbose exif2c08.png
> >     > exif3p08.png":
> >     >
> >     > Image: exif2c08.png
> >     >   Format: PNG (Portable Network Graphics)
> >     >   Type: Palette
> >     >   Properties:
> >     >     date:create: 2017-01-30T16:59:38-05:00
> >     >     date:modify: 2017-01-30T16:58:06-05:00
> >     >     exif:ColorSpace: 65535
> >     >     exif:ComponentsConfiguration: 1, 2, 3, 0
> >     >     exif:Copyright: 2017 Willem van Schaik
> >     >     exif:ExifOffset: 138
> >     >     exif:ExifVersion: 48, 50, 50, 48
> >     >     exif:FlashPixVersion: 48, 49, 48, 48
> >     >     exif:Orientation: 1
> >     >     exif:ResolutionUnit: 2
> >     >     exif:thumbnail:Compression: 6
> >     >     exif:thumbnail:JPEGInterchangeFormat: 314
> >     >     exif:thumbnail:JPEGInterchangeFormatLength: 663
> >     >     exif:thumbnail:ResolutionUnit: 2
> >     >     exif:thumbnail:XResolution: 72/1
> >     >     exif:thumbnail:YResolution: 72/1
> >     >     exif:UserComment: 65, 83, 67, 73, 73, 0, 0, 0, 80, 110, 103,
> 83,
> >     > 117, 105, 116, 101
> >     >     exif:XResolution: 72/1
> >     >     exif:YCbCrPositioning: 1
> >     >     exif:YResolution: 72/1
> >     >     png:IHDR.bit-depth-orig: 8
> >     >     png:IHDR.bit_depth: 8
> >     >     png:IHDR.color-type-orig: 2
> >     >     png:IHDR.color_type: 2 (Truecolor)
> >     >     png:IHDR.interlace_method: 0 (Not interlaced)
> >     >     png:IHDR.width,height: 32, 32
> >     >     png:sRGB: intent=0 (Perceptual Intent)
> >     >     signature:
> >     > 783704a680ad00e885dc84076dc26dfa3159c376798f2644afa4aa6a47f2c0cb
> >     >   Profiles:
> >     >     Profile-exif: 984 bytes
> >     >   Version: ImageMagick 7.0.4-6 Q16 x86_64 2017-01-28
> >     > http://www.imagemagick.org
> >     > Image: exif3p08.png
> >     >   Format: PNG (Portable Network Graphics)
> >     >   Type: Palette
> >     >   Properties:
> >     >     date:create: 2017-01-30T16:59:38-05:00
> >     >     date:modify: 2017-01-30T16:58:26-05:00
> >     >     exif:ColorSpace: 65535
> >     >     exif:ComponentsConfiguration: 1, 2, 3, 0
> >     >     exif:Copyright: 2017 Willem van Schaik
> >     >     exif:ExifOffset: 138
> >     >     exif:ExifVersion: 48, 50, 50, 48
> >     >     exif:FlashPixVersion: 48, 49, 48, 48
> >     >     exif:Orientation: 1
> >     >     exif:ResolutionUnit: 2
> >     >     exif:thumbnail:Compression: 6
> >     >     exif:thumbnail:JPEGInterchangeFormat: 314
> >     >     exif:thumbnail:JPEGInterchangeFormatLength: 663
> >     >     exif:thumbnail:ResolutionUnit: 2
> >     >     exif:thumbnail:XResolution: 72/1
> >     >     exif:thumbnail:YResolution: 72/1
> >     >     exif:UserComment: 65, 83, 67, 73, 73, 0, 0, 0, 80, 110, 103,
> 83,
> >     > 117, 105, 116, 101
> >     >     exif:XResolution: 72/1
> >     >     exif:YCbCrPositioning: 1
> >     >     exif:YResolution: 72/1
> >     >     png:IHDR.bit-depth-orig: 8
> >     >     png:IHDR.bit_depth: 8
> >     >     png:IHDR.color-type-orig: 3
> >     >     png:IHDR.color_type: 3 (Indexed)
> >     >     png:IHDR.interlace_method: 0 (Not interlaced)
> >     >     png:IHDR.width,height: 32, 32
> >     >     png:PLTE.number_colors: 134
> >     >     png:sRGB: intent=0 (Perceptual Intent)
> >     >     signature:
> >     > e4818fcc46a06587c1ba53cf753e938ce6ae63a116946a8a5fe7a20741d61d9e
> >     >   Profiles:
> >     >     Profile-exif: 984 bytes
> >     >
> >     > glenn.rp>
> >     >
> >     >
> >     >
> >     >
> >     >
> >     > ------------------------------------------------------------
> ------------------
> >     > Check out the vibrant tech community on one of the world's most
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> >     >
> >     >
> >     >
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> >     >
> >
> >     --
> >     Willem van Schaik
> >     [email protected] <mailto:[email protected]>
> >
> >     ------------------------------------------------------------
> ------------------
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> >
> >
> >
> >
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>
> --
> Willem van Schaik
> [email protected]
>
> ------------------------------------------------------------
> ------------------
> Check out the vibrant tech community on one of the world's most
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