[Gimp-developer] Proposed usabillity enhancement for PNG handling

[Alexia Death]

On Mon, Oct 13, 2008 at 9:07 PM, Sven Neumann <sven at gimp.org> wrote:

> On Sun, 2008-10-12 at 21:26 +0300, Alexia Death wrote:
>
> > PNG-s support offset for whatever renders them in the file format.
>
> What's the purpose of these offsets? I find it difficult to judge your
> proposal without knowing what the spec says about this.
>
I looked up the PNG spec about this already when first trying to decide if
it was a bug or a feature.

To the letter spec says:
"The oFFs chunk gives the position on a printed page at which the image
should be output when printed alone. It can also be used to define the
image's location with respect to a larger screen or other
application-specific coordinate system."

I see it mainly as a a directive to the rendering engine to place the image
at a offset. Its useful in contexts where PNG-s are used for rendering an UI
etc. and supporting it is good. But in current implementation it is a
hindrance to editing without any added benefits even to the user that WANTS
to use it(see described use case in the first ). Now looking at spec,
specially the last sentence, as I understand it these fields could be used
to define an offset in a coordiante system totaly different of PNG-s own,
with makes the way gimp handles it now totally incorrect for those usecases.
The image can be unedtable because the system using it has a larger
coordinate system and it ends up 100% outside canvas.

--Alexia
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