Yes, piece of cake.
I'm going to assume that you're using ImageInput. (If you are using an
ImageBuf-based pipeline, let me know.) You probably have an open sequence that
looks something like this:
auto inp = ImageInput::open("foo.tif");
ImageSpec spec = inp->spec(0, 0);
Let's say you have allocated a 4-channel buffer,
float *buf = new float [yres * xres * 4];
and you want to read the first 3 channels of the image into the right positions
of this buffer, but leave the 4th channel of each pixel's slot in the buffer
unaltered.
All of the ImageInput::read_* functions take optional stride parameters. So you
just specify the right strides:
inp->read_image(/*subimage*/ 0, /*miplevel*/ 0, /*chbegin*/ 0, /*chend*/ 3,
OIIO::TypeFloat, buf,
/*xstride*/ 4 * sizeof(float));
this will leave the [3] positions in each pixel untouched. You can fill them in
with 1.0 or whatever on your own, maybe like
for (int i = 0; i < xres * yres; ++i)
buf[i*4 + 3] = 1.0f;
> On Sep 7, 2022, at 3:15 AM, Bartłomiej Styczeń <[email protected]> wrote:
>
> Hi,
>
> OIIO is an amazing piece of software, saving me an enormous amount of time
> and headache. In my case it unfortunately has to be interfaced with QT's
> QImage container, which is quite limited in what image formats it
> understands. The one I'm lacking is a 3-channel float image. Floats are
> crucial for the use case.
>
> I need to be able to read all kinds of images into an uniform buffer - RGBA
> float.
> For example, if an image only has 3 channels, I'd fill the A values with
> 1.0f. So far I am doing this by just copying the RGB buffer into a RGBA one
> pixel by pixel and adding the alpha values. This of course is absolutely
> wasteful and slow, it would be perfect if I could somehow instruct OCIO to
> read any images into an RGBA format buffer.
>
> Trying to simply set the ImageSpec to the desired channel number and ordering
> results in images being read improperly.
>
> Is there a straightforward way to do this? Any help is greatly appreciated.
>
> Best regards,
>
> Bart Styczen,
> CineDev
>
> _______________________________________________
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> [email protected]
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--
Larry Gritz
[email protected]
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