There are very few such configuration options now. I'll keep this on the back
burner, but I guess if I did the work now to make this general, it wouldn't
have any widespread use.
Glad the workaround seems to do the trick.
-- lg
On Jun 13, 2014, at 11:08 AM, Nicolas Burtnyk <[email protected]> wrote:
> For us it's not particularly common and the workaround is simple enough, so I
> would say it's low priority to provide a direct way to do this with ImageBuf.
> That being said, if there are spec attributes that affect how images are
> read, IMO it's reasonable to assume you could specify those attributes when
> using ImageBuf.
>
>
>
> On Fri, Jun 13, 2014 at 11:05 AM, Larry Gritz <[email protected]> wrote:
> Great.
>
> Is this a common enough problem that we should have a direct way to tell
> ImageBuf to do this upon load? Or is it a one-time edge case you just needed
> a workaround for and will probably not recur?
>
> -- lg
>
>
> On Jun 13, 2014, at 11:02 AM, Nicolas Burtnyk <[email protected]> wrote:
>
>> Thanks Larry,
>>
>> We went with a variation on technique #2.
>>
>> Cheers,
>>
>> -Nicolas
>>
>> On Thu, Jun 12, 2014 at 10:12 AM, Larry Gritz <[email protected]> wrote:
>> There is a way to do this with plain ImageInput. One variety of
>> ImageInput::open take a "configuration", which you can seed with an
>> attribute called "oiio:UnassociatedAlpha" (set to 1) that instructs the TGA
>> reader to not premultiply the RGB by the A.
>>
>> ImageSpec config;
>> config.attribute ("oiio:UnassociatedAlpha", 1);
>> ImageInput *in = ImageInput::open (filename, &config);
>> const ImageSpec &spec = in->spec();
>> std::vector<unsigned char> pixels
>> (spec.width*spec.height*spec.channels);
>> in->read_image (TypeDesc::UINT8, &pixels[0]);
>> in->close ();
>> delete in;
>>
>> There's not a very clean way to do this with an ImageBuf.
>>
>> I suppose one strategy is to create a blank ImageBuf, then read into it in a
>> variation of the above. Instead of declaring that std::vector, you could do
>> this:
>>
>> ImageSpec config;
>> config.attribute ("oiio:UnassociatedAlpha", 1);
>> ImageInput *in = ImageInput::open (filename, &config);
>> const ImageSpec &spec = in->spec();
>> ImageBuf buf;
>> buf.alloc (spec); // size it based on the input image
>> in->read_image (TypeDesc::UINT8, buf.localpixels());
>> in->close ();
>> delete in;
>>
>> And then proceed to use the ImageBuf as you always would.
>>
>> I admit this is kind of clunky. It's probably better to add some kind of
>> method to ImageBuf that lets you specify a "configuration" that will be
>> applied when the file is opened and read.
>>
>>
>>
>> On Jun 9, 2014, at 8:56 PM, Nicolas Burtnyk <[email protected]> wrote:
>>
>>> We're running into an issue with where we're using ImageBuf to read a TGA
>>> file which happens to have an alpha channel filled with zeros. We want to
>>> grab the data in the red and green channels without an premultiplication
>>> (otherwise they're just all 0). Is this currently possible with ImageBuf?
>>>
>>> Thanks!
>>>
>>> Nicolas
>>
>>
>
> --
> Larry Gritz
> [email protected]
>
>
>
>
> _______________________________________________
> Oiio-dev mailing list
> [email protected]
> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org
>
>
> _______________________________________________
> Oiio-dev mailing list
> [email protected]
> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org
--
Larry Gritz
[email protected]
_______________________________________________
Oiio-dev mailing list
[email protected]
http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org
