Re: TIFFRepresentation, different TIFF format under Snow Leopard
Re: TIFFRepresentation, different TIFF format under Snow Leopard
- Subject: Re: TIFFRepresentation, different TIFF format under Snow Leopard
- From: Ken Ferry <email@hidden>
- Date: Tue, 13 Oct 2009 08:22:27 -0700
On Mon, Oct 12, 2009 at 11:48 AM, Sander Stoks <email@hidden> wrote:
> I have a related question. The various image file formats have their own
> options and settings (compression levels, color space, interlacing, etc.);
> is there a generic way to access these from within my application?
>
> For those who still remember BeOS (where the grass was green and the girls
> were pretty), there was a concept called "Translators" (which BeOS, in turn,
> borrowed from the Amiga). Each Translator was basically an Image I/O codec,
> but you could also query them for a "configuration view" which you could
> simply show in your own application. That way, the app doesn't have to know
> the ins and outs of all the file formats.
>
> Does something like this exist on MacOS or do I have to create these
> settings views myself?
>
Yes, though I'm sure it isn't precisely the same.
Take a look at IKSaveOptions.
Ken Ferry
Cocoa Frameworks
>
> Regards,
> Sander
>
>
> Actually, that occurred under 10.5 as well - what happens is that some
>> operations, it would seem those involving Core Image, cause the
>> internal representation to go to RGBA. Which is fine, but there
>> doesn't seem to be a way to write a plain RGB format TIFF. I had to
>> incorporate a third-party TIFF module to do that, as RGBA TIFF files
>> aren't very compatible with anything other than Apple.
>>
>> Sandy
>>
>>
>> On Oct 12, 2009, at 5:07 PM, Ken Ferry wrote:
>>
>> On Mon, Oct 12, 2009 at 4:36 AM, Peter C <email@hidden>
>>> wrote:
>>>
>>> I just stumble into a feature (or a bug ?), NSImage
>>>> TIFFRepresentation
>>>> produce RGB TIFF with a layer (when open under Photoshop).
>>>> Previously it
>>>> produce plain RGB TIFF under OS 10.5 and below. This cause some
>>>> part of my
>>>> programs interpret wrong RGB data, expecting 3 bytes instead of 4
>>>> bytes for
>>>> a RGB pixel. There is no mention in the documents about this
>>>> "feature".
>>>>
>>>> Is there a way to restore the previous behavior of
>>>> TIFFRepresentation ?
>>>>
>>>
>>>
>>> You can look at CGImageDestination to get more options, but I don't
>>> think
>>> there's anything that provides control at that level.
>>>
>>> In many cases there _must_ be data munging between the in memory pixel
>>> format and the on-disk file format. The precise munging is not
>>> defined on
>>> either input or output.
>>>
>>> That is, don't make pixel format assumptions. The AppKit release
>>> notes<
>>> http://developer.apple.com/mac/library/releasenotes/Cocoa/AppKit.html
>>>
>>>> discuss
>>>>
>>> how to avoid making pixel format assumptions in the section
>>> "NSBitmapImageRep: CoreGraphics impedence matching and performance
>>> notes".
>>>
>>> -Ken
>>>
>>
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