[Oiio-dev] multi page vs multi layered tiff, or ps compatible tiff

Larry Gritz lg at larrygritz.com
Tue Aug 18 23:13:19 PDT 2020


I had found that, yes.

Right, I did understand that much -- that the TIFF file contains in its header a tag 37724 which is PhotoShop specific information and contains a blob of information written by PS which encodes all the layering information.

But...

The documentation about what exactly is in that data block, what it all means, and how OIIO would encode a compliant layer information data block while writing a TIFF file that would reliably be interpreted correctly by PhotoShop... that is not at all clear.

	-- lg


> On Aug 18, 2020, at 1:14 PM, Johannes Hezer <johannes.hezer at googlemail.com> wrote:
> 
> Hey Larry, 
> thank you for looking into this. 
> https://www.imagemagick.org/discourse-server/viewtopic.php?t=26785 <https://www.imagemagick.org/discourse-server/viewtopic.php?t=26785>
> This old thread from imgmagick reflects the same...
> 
> https://www.adobe.io/content/dam/udp/en/open/standards/tiff/TIFFphotoshop.pdf <https://www.adobe.io/content/dam/udp/en/open/standards/tiff/TIFFphotoshop.pdf>
> Page 11 mentions Layers...
> 
> This is the text from page 11
> """
> Image Source Data Introduction This section describes the Adobe Photoshop specific image source data tag. This section has the layer and mask information found in a typical layered Photoshop file. Field: ImageSourceData Tag: 37724 (935C.H) Type: UNDEFINED Count: number of bytes for section The section starts with a character string of "Adobe Photoshop Document Data Block" including the null termination character. The remainder of the count, after subtracting the length of the above mentioned string, is a series of tagged data types in the following format: 4 bytes Signature ‘8BIM’ 4 bytes Type various types (see below) 4 bytes Length length in bytes, variable for each type, padded to a 4 byte offset The various types are mentioned here with further documentation in the Photoshop File Formats.pdf. The available types are: ‘Layr’ Layer Data ‘LMsk’ User Mask Same as Global layer mask info table ‘Patt’ Pattern ‘Anno’ Annotations
> 
> """
> Does this eventually help at least understanding what adobe is doing there ?
> 
> All the best
> 
> Johannes
> 
> 
> 
> Am 15.08.20 um 8:10 am schrieb Larry Gritz:
>> OK, the layered.tif is definitely not a multi-subimage file. It seems that it's just one subimage (maybe the merged layers?) but there is a special data block in the header containing encoded PhotoShop information, which presumably contains whatever PS needs to represent the layer information. But unfortunately, it's a proprietary tag that is not documented. I'm not sure how we could reliably write TIFF files and embed that data.
>> 
>> 	-- lg
>> 
>> 
>>> On Aug 12, 2020, at 11:18 PM, Johannes Hezer <johannes.hezer at googlemail.com <mailto:johannes.hezer at googlemail.com>> wrote:
>>> 
>>> Hey Larry,
>>> 
>>> attached is an archive with 5 files, one layered.tif from PS, then all three seperate and one created with oiio --siappendall, called multipage_tif...
>>> Thanks, for looking into this.
>>> 
>>> All the best
>>> Johannes
>>> 
>>> Am 12.08.20 um 17:16 pm schrieb Larry Gritz:
>>>> I'm not quite sure what a "multi layered tiff" is, from PS's perspective. Do you have an example of a TIFF file (doesn't have to have been written by OIIO) that does correctly behave in the way you want when opened by PS? Send it to me and maybe I can see how exactly it's laid out and figure out what is the missing ingredient.
>>>> 
>>>> 	-- lg
>>>> 
>>>> 
>>>>> On Aug 12, 2020, at 6:09 AM, Johannes Hezer <johannes.hezer at googlemail.com <mailto:johannes.hezer at googlemail.com>> wrote:
>>>>> 
>>>>> Hey,
>>>>> 
>>>>> I was wondering if anybody has achieved writing a tiff that works in PS as a multi layered tiff.
>>>>> 
>>>>> oiiotool a.tif b.tif c.tif --siappendall -o out.tif creates a multipage tif, which apparently opens fine in almost any tif enabled program on the planet, but ps only reads in the first page...
>>>>> 
>>>>> Any ideas?
>>>>> 
>>>>> All the best
>>>>> 
>>>>> Johannes
>>>> 
>>>> --
>>>> Larry Gritz
>>>> lg at larrygritz.com <mailto:lg at larrygritz.com>
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
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>>> 
>>> <tif_test.zip>_______________________________________________
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>> 
>> --
>> Larry Gritz
>> lg at larrygritz.com <mailto:lg at larrygritz.com>
>> 
>> 
>> 
>> 
>> 
>> 
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> 
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--
Larry Gritz
lg at larrygritz.com




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