Aha, there does seem to be a bug. The docs say that render_text ought to be
doing an "over", but you are right, it's not behaving that way at all!
Your understanding of what *should* happen is also how I thought it worked.
It's just a mistake somewhere, I will try to find a fix.
-- lg
> On May 27, 2021, at 12:35 AM, Daniel Flehner Heen <flehnerhee...@gmail.com>
> wrote:
>
> Hi Larry!
>
> Apologize for the lack of response.
>
> Inspecting the values indeed show variations in the alpha channel, so it
> works and this turns out to be a case of misconception from my side.
> I assumed that render_text would do an "over" and that by setting alpha of
> text color to values below 1 would yield "see through" text rather than
> directly manipulating the pixels in the buffer.
>
> Thank you for your help!
>
>
>
> On Tue, May 25, 2021 at 9:31 PM Larry Gritz <l...@larrygritz.com
> <mailto:l...@larrygritz.com>> wrote:
> Sorry, of course I meant (1+0.6*something). The 0.4 is opacity, not
> transparency.
>
> A over B = A + (1-A.alpha)*B
>
>
>> On May 25, 2021, at 12:30 PM, Larry Gritz <l...@larrygritz.com
>> <mailto:l...@larrygritz.com>> wrote:
>>
>> Well, you have set the text color to (1,1,1,0.4), so if you put that "over"
>> an image, then write to (or display on) a LDR device or file, the resulting
>> "clamp" to the full intensity of the output will not be distinguishable from
>> if it were opaque. But if you are inspecting values in an HDR format like
>> OpenEXR, then the values of text (1,1,1,0.4) over "something" will be
>> (1+0.4*something, ...), whereas opaque (1,1,1,1) over "something" will be
>> exactly (1.0, ...) no matter what the something is. Note that for both of
>> those, if clamped to a max of 1.0, they will look the same.
>>
>>
>>> On May 25, 2021, at 12:18 PM, Daniel Flehner Heen <flehnerhee...@gmail.com
>>> <mailto:flehnerhee...@gmail.com>> wrote:
>>>
>>> Hmmm. I've only checked visually, but when rendering on an image I can't
>>> see through the text. If you get transparency I must be doing something
>>> wrong.
>>> I'm not in front of a computer at the moment, but I'll try and break down
>>> my process and see if I can figure it out.
>>> I'll let you know what I find.
>>>
>>> Thanks,
>>>
>>>
>>>
>>>
>>>
>>> On Tue, May 25, 2021, 21:01 Larry Gritz <l...@larrygritz.com
>>> <mailto:l...@larrygritz.com>> wrote:
>>> Works for me. How are you determining that there is "no difference in
>>> transparency"? Are you inspecting the alpha values in the output file? Are
>>> you compositing on top of something?
>>>
>>>
>>>> On May 25, 2021, at 11:58 AM, Daniel Flehner Heen <flehnerhee...@gmail.com
>>>> <mailto:flehnerhee...@gmail.com>> wrote:
>>>>
>>>> Sorry, should have been more specific.
>>>> There seems to be no difference in the text's transparency for values
>>>> between 0.1 and 1.0 for the alpha channel.
>>>>
>>>> On Tue, May 25, 2021, 20:48 Larry Gritz <l...@larrygritz.com
>>>> <mailto:l...@larrygritz.com>> wrote:
>>>> What happens, specifically?
>>>>
>>>>
>>>>> On May 25, 2021, at 6:31 AM, Daniel Flehner Heen <flehnerhee...@gmail.com
>>>>> <mailto:flehnerhee...@gmail.com>> wrote:
>>>>>
>>>>> Hi!
>>>>>
>>>>> I'm attempting to render text with 40% opacity in python without success.
>>>>> OIIO 2.2.10.1
>>>>>
>>>>> ``` python
>>>>> import OpenImageIO as oiio
>>>>> buf = oiio.ImageBuf(oiio.ImageSpec(640, 480, 4 oiio.FLOAT))
>>>>> oiio.ImageBufAlgo.render_text(buf, 100, 200, "Hello, World!", 60,
>>>>> "FreeSans", (1, 1, 1, 0.4))
>>>>> buf.write('transparent_text_test.exr')
>>>>> ```
>>>>>
>>>>> Am I doing something wrong?
>>>>> Any pointers would be greatly appreciated.
>>>>>
>>>>> Thanks,
>>>>>
>>>>> --
>>>>> -Daniel
>>>>> _______________________________________________
>>>>> Oiio-dev mailing list
>>>>> Oiio-dev@lists.openimageio.org <mailto:Oiio-dev@lists.openimageio.org>
>>>>> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org
>>>>> <http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org>
>>>>
>>>> --
>>>> Larry Gritz
>>>> l...@larrygritz.com <mailto:l...@larrygritz.com>
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
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>>>
>>> --
>>> Larry Gritz
>>> l...@larrygritz.com <mailto:l...@larrygritz.com>
>>>
>>>
>>>
>>>
>>> _______________________________________________
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>>
>> --
>> Larry Gritz
>> l...@larrygritz.com <mailto:l...@larrygritz.com>
>>
>>
>>
>>
>
> --
> Larry Gritz
> l...@larrygritz.com <mailto:l...@larrygritz.com>
>
>
>
>
> _______________________________________________
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>
>
> --
> -Daniel
> _______________________________________________
> Oiio-dev mailing list
> Oiio-dev@lists.openimageio.org
> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org
--
Larry Gritz
l...@larrygritz.com
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