Yep, I'm good with that. Thanks again for teasing this apart Larry/HP
~Andrew On Fri, Feb 19, 2016 at 10:09 AM, Larry Gritz <[email protected]> wrote: > OK, that sounds reasonable. So we have: > > * If you ask for a specific type, convert and return an array of that > type. If you ask for HALF, the half bit pattern gets returned in a uint16 > array, since there is no true half type. > > * If you ask for UNKNOWN (explicitly "give me raw data"), it returns an > array of unsigned chars containing the raw data. > > Everybody can live with that? > > > On Feb 19, 2016, at 8:08 AM, Haarm-Pieter Duiker <[email protected]> > wrote: > > Of the options "pass half values disguised as an unsigned short array" > feels the cleanest to me. You keep the right number of components in the > array, if you have any checks for that, and the data to be convert to halfs > is already grouped appropriately. > > Converting to halfs is also a one line call to numpy: > np.frombuffer(np.getbuffer(np.uint16(uint16Value)), dtype=np.float16) > Ex. https://github.com/hpd/CLF/blob/master/python/aces/clf/Common.py#L92 > > HP > > > > > > On Thu, Feb 18, 2016 at 4:06 PM, Larry Gritz <[email protected]> wrote: > >> In C++, asking for UNKNOWN just copies the native format data and leaves >> it for you to sort out. But to C++, a buffer is a buffer, you're passing it >> a void* in any case. >> >> In Python, it's dynamic typing, so read_image RETURNS an array, and it >> has to be an array of some type. Which type? >> >> I think we all are coming to agree that if you ask for UNKNOWN, probably >> the most analogous thing (to C++) is to return an unsigned char array, >> filled with the raw data, and leave you to sort it out. That's as close to >> "untyped raw buffer" as we can get. >> >> If you *ask* for HALF, it's nonsensical, because you can't make an actual >> half array in Python. You could promote and convert it to float. Or you >> could return raw values in unsigned char array (like if you'd passed >> UNKNOWN). Or, yeah, another possibility is to pass half values disguised as >> an unsigned short array? >> >> I'm not super fond of the last choice. >> >> Right now, we do something stupider than any of those -- which is to pack >> raw half values into a buffer, but the buffer advertises itself as being a >> float array. That clearly needs to change. It was never intentional; I just >> never thought carefully about that case because I never imagined anybody >> asking for a type that didn't exist in Python. >> >> So, current proposal on the table: >> >> * If you ask for a type that can be a valid Python array type, convert >> and return an array of that type. >> >> * If you ask for UNKNOWN (explicitly "give me raw data") or HALF >> (implicitly so, because it doesn't exist in Python), it returns an array of >> unsigned chars containing the raw data. >> >> >> >> On Feb 18, 2016, at 3:36 PM, Haarm-Pieter Duiker <[email protected]> >> wrote: >> >> Returning a series of unsigned 16 bit ints for a call with the type half >> feels like a nice middle ground. The consumer will have to know that halfs >> aren't natively supported in Python, and how to convert from unsigned short >> to half, but that doesn't feel like a large burden. >> >> I can't speak to the expected behavior of the UNKNOWN in Python. I >> haven't used that path in Python or C++. >> >> HP >> >> >> >> >> >> >> >> >> On Thu, Feb 18, 2016 at 1:23 PM, Larry Gritz <[email protected]> wrote: >> >>> I don't have especially strong feelings about this one way or the other. >>> >>> Just returning a raw data byte array matches the C++ behavior more >>> closely, no argument there. >>> >>> On the "con" side, perhaps I was thinking of compatibility? We're really >>> talking about changing the meaning of oiio.UNKNOWN from "use spec.format" >>> to "return raw data", which differ in the case of mixed channel types. >>> >>> Are there Python programs out there that pass UNKNOWN (or pass nothing, >>> defaulting to UNKNOWN) and rely on getting the right kind of array back >>> that matches spec.format? >>> >>> >>> >>> >>> On Feb 18, 2016, at 12:58 PM, Andrew Gartner <[email protected]> >>> wrote: >>> >>> "Second, I could collapse 2a and 2b, and just say that if you ask for >>> UNKNOWN, you get an array of uint8 back with the native raw data" >>> >>> Just out of curiosity, what are the drawbacks to doing this? I admit I >>> like having some way of getting at the raw data at any time (hence my >>> original method of exposing the native calls). That allowed me to check my >>> imagespec and regardless of whether I had a mixed format image or all half >>> data I could get everything in one read call. Granted I'm used to keeping >>> track of and manipulating the strides of those arrays in bytes just out of >>> old habit (and C++ usage) so maybe I'm the minority opinion. >>> >>> Even so, your current thinking still works if that's where the consensus >>> is I'm happy to use it as such. >>> >>> Thanks again >>> >>> ~Andrew >>> >>> On Thu, Feb 18, 2016 at 12:21 PM, Larry Gritz <[email protected]> wrote: >>> >>>> I think that the only format that we can encounter as pixel data, which >>>> does not exist in Python arrays, is 'half'. >>>> >>>> So let me rephrase my current thinking: >>>> >>>> 1. If you ask for a specific type (except HALF), you'll get a Python >>>> array of that type holding the converted values. >>>> >>>> 2. Otherwise (i.e., you ask for UNKNOWN or HALF), you will get the >>>> native (raw) data. >>>> (a) If all channels are the same data type and it's anything but half, >>>> you'll get the data as a Python array of that type. >>>> (b) Otherwise (half, or mixed channel types), you'll get the data as a >>>> Python array of unsigned bytes. >>>> >>>> Note that (1) is the easy case to deal with: ask for the type you want, >>>> let it do the conversion. If you go for option (2) by asking for native >>>> data, you get a blob and it's up to you to figure out what to do with it. >>>> >>>> There are two other choices we could make. I'm not inclined to at the >>>> moment, but would be happy to do so if people think it's helpful. First, if >>>> you ask for HALF, I could have it return float. Second, I could collapse 2a >>>> and 2b, and just say that if you ask for UNKNOWN, you get an array of uint8 >>>> back with the native raw data, even if it happened to be all channels of >>>> the same type, a type that you could have made into a Python array of the >>>> right type. >>>> >>>> >>>> On Feb 17, 2016, at 11:16 PM, Haarm-Pieter Duiker < >>>> [email protected]> wrote: >>>> >>>> Picking this up a little later in the day. Sorry about that. Adding >>>> quotes from earlier in the thread just so it's clear what I'm responding >>>> to. >>>> >>>> The current status: >>>> " >>>> If you read_image(oiio.FLOAT) of a half image (on disk), you get floats >>>> back? >>>> " >>>> Yes. >>>> >>>> " >>>> But if you read_image(oiio.HALF) of a half image, you get what appears >>>> to be an array of floats, but they are actually packed half values? >>>> " >>>> Yes. >>>> >>>> The proposal: >>>> " >>>> 1. If you ask for a (non-UNKNOWN) format that exists in Python, it >>>> converts to and returns an array of that format. >>>> " >>>> This is the current behavior, no? >>>> >>>> " >>>> 2. If you ask for UNKNOWN, or a format that doesn't exist, it returns >>>> the raw data in an unsigned char array. >>>> " >>>> It feels like this is two proposals (Trying not to clash with your >>>> earlier 2a and 2b): >>>> 2c. If you ask for UNKNOWN, return raw data in an unsigned char array >>>> 2d. If you ask for a format that doesn't exist, return raw data in an >>>> unsigned char array >>>> >>>> 2c. feels right. It should work for the case of typical RGB or RGBA >>>> images but also for multi-layer EXRs. The consumer can convert the channels >>>> to their intended types using methods from the ImageSpec. I'd suggest that >>>> asking for UNKNOWN lead unequivocally to a raw unsigned char array. >>>> Supporting the special cases described in the 2a and 2b listed earlier >>>> would require additional logic on the consuming code side to account for >>>> those cases. Feels like a recipe for lots of brittle special case logic. >>>> >>>> 2d. is less clear. How is the change in behavior from returning real >>>> values for known types to returning raw char array data for unknown types >>>> signaled to the consumer? Is this still something that programmers have to >>>> just know a priori? How is this different from the current behavior? >>>> >>>> I suppose the list of types known to OIIO but not Python is finite and >>>> likely to shrink over time. Having special cases like we have in that >>>> example code, isn't such a big deal in the mean time, but then that's just >>>> saying the the current behavior is fine. >>>> >>>> Hope that's helpful in some way. Aside from agreeing that adding an >>>> UNKNOWN option is a good idea, we're still left without a good way to >>>> consume half data without accounting for it explicitly. >>>> >>>> HP >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> On Wed, Feb 17, 2016 at 4:35 PM, Andrew Gartner < >>>> [email protected]> wrote: >>>> >>>>> That would certainly take care of things for me. Hopefully not too >>>>> much of an impact on others as well. >>>>> >>>>> ~Andrew >>>>> >>>>> >>>>> >>>>> On Wed, Feb 17, 2016 at 4:20 PM, Larry Gritz <[email protected]> >>>>> wrote: >>>>> >>>>>> So I'm proposing: >>>>>> >>>>>> 1. If you ask for a (non-UNKNOWN) format that exists in Python, it >>>>>> converts to and returns an array of that format. >>>>>> >>>>>> 2. If you ask for UNKNOWN, or a format that doesn't exist, it returns >>>>>> the raw data in an unsigned char array. >>>>>> >>>>>> >>>>>> There is a variation: >>>>>> >>>>>> 2a. If you ask for UNKNOWN, and all channels are the same format and >>>>>> it's a type that exists in Python, return that type. >>>>>> 2b. If you ask for UNKNOWN and it's a "mixed type" file, or a single >>>>>> type but one that doesn't exist in Python, or the type you ask for >>>>>> doesn't >>>>>> exist in Python, return raw data packed into an unsigned char array. >>>>>> >>>>>> >>>>>> >>>>>> On Feb 17, 2016, at 4:10 PM, Andrew Gartner <[email protected]> >>>>>> wrote: >>>>>> >>>>>> Yea the C++ implementation works well with oiio.UNKNOWN, I kinda miss >>>>>> that in the python side to be honest. Right now it looks like things >>>>>> revert >>>>>> back to spec.format if oiio.UNKNOWN is supplied to read_scanlines, that >>>>>> can >>>>>> be problematic if you have multiple formats in a single image so I've >>>>>> avoided it. >>>>>> >>>>>> @Larry, to you question about returning an unsigned char array, I >>>>>> like the idea on principle in that it preserves the decoupling as you >>>>>> said. >>>>>> I'm wondering if there would be any weirdness if you had to grab multiple >>>>>> channels of an image that had different data types one of which isn't >>>>>> representable in python? Would it default to just unsigned char yet again >>>>>> in that case? >>>>>> >>>>>> @Haarm: interesting, I didn't realize they were concatenated/packed >>>>>> like that! I just saw the 'f' in the python array and assumed I was >>>>>> seeing >>>>>> promoted values :) I'm still scratching my head over the multiple format >>>>>> reads though, same as for Larry's idea. >>>>>> >>>>>> Thanks for the replies, Cheers, >>>>>> >>>>>> ~Andrew >>>>>> >>>>>> >>>>>> >>>>>> On Wed, Feb 17, 2016 at 3:49 PM, Haarm-Pieter Duiker < >>>>>> [email protected]> wrote: >>>>>> >>>>>>> If you're up for using numpy, this will get you the half float >>>>>>> values without too much extra work: >>>>>>> oiioFloats = inputImage.read_image(oiio.HALF) >>>>>>> oiioHalfs = np.frombuffer(np.getbuffer(np.float32(oiioFloats)), >>>>>>> dtype=np.float16) >>>>>>> >>>>>>> One note, the current OIIO Python implementation doesn't promote the >>>>>>> halfs to float on read. The 'float' values in the returned buffer are >>>>>>> actually each two concatenated half values, and the float buffer will >>>>>>> have >>>>>>> half as many entries as you would expect. >>>>>>> >>>>>>> Example usage for reading here: >>>>>>> >>>>>>> https://github.com/hpd/CLF/blob/master/python/aces/filterImageWithCLF.py#L126 >>>>>>> and the reverse for writing: >>>>>>> >>>>>>> https://github.com/hpd/CLF/blob/master/python/aces/filterImageWithCLF.py#L193 >>>>>>> >>>>>>> HP >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Wed, Feb 17, 2016 at 3:25 PM, Larry Gritz <[email protected]> >>>>>>> wrote: >>>>>>> >>>>>>>> In C++, you can just call read_scanlines and pass format=UNKNOWN to >>>>>>>> get back the raw data in its original format. >>>>>>>> >>>>>>>> The problem is that in Python, there is no 'half' so it's not quite >>>>>>>> sure what to return. >>>>>>>> >>>>>>>> I kinda like the decoupling of the raw reads (read_native_*) which >>>>>>>> are the part overloaded by the individual format readers, from the >>>>>>>> app-callable read_*. So perhaps rather than exposing read_native_*, we >>>>>>>> should just modify the Python bindings for read_* to notice that if the >>>>>>>> native raw data is not a type representable in Python, to return it as >>>>>>>> an >>>>>>>> unsigned character array? >>>>>>>> >>>>>>>> >>>>>>>> > On Feb 17, 2016, at 2:55 PM, Andrew Gartner < >>>>>>>> [email protected]> wrote: >>>>>>>> > >>>>>>>> > Hey all, >>>>>>>> > >>>>>>>> > Apologies if this has come up before, but I'm curious if anyone >>>>>>>> had considered exposing ImageInput.read_native_scanlines() on the >>>>>>>> python >>>>>>>> side before. The reason I ask is mainly because the half datatype >>>>>>>> doesn't >>>>>>>> exist in the native python array class which OIIO uses for python >>>>>>>> reads. >>>>>>>> Currently the python array will punt and for anything to float (which >>>>>>>> I'd >>>>>>>> rather avoid). >>>>>>>> > >>>>>>>> > I had put together an implementation in OIIO 1.5 that simply took >>>>>>>> the pixel size as a parameter and exposed read_native_scanlines that >>>>>>>> way >>>>>>>> and that allowed me to get the right data properly into either numpy >>>>>>>> or a >>>>>>>> raw char python array. However, I'd rather not be forked off like that >>>>>>>> as >>>>>>>> it's a headache trying to remain current with the mainline, plus >>>>>>>> others may >>>>>>>> find it useful. >>>>>>>> > >>>>>>>> > Does anyone think exposing the function in general makes sense? >>>>>>>> I'm happy to send the implementation if anyone cares to see it as well. >>>>>>>> > >>>>>>>> > Cheers, >>>>>>>> > >>>>>>>> > ~Andrew >>>>>>>> > >>>>>>>> >>>>>>>> -- >>>>>>>> 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 >>>>>>> >>>>>>> >>>>>> _______________________________________________ >>>>>> 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 >>>>>> >>>>>> >>>>> >>>>> _______________________________________________ >>>>> 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 >>>> >>>> >>> _______________________________________________ >>> 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 >>> >>> >> _______________________________________________ >> 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 >> >> > _______________________________________________ > 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 > >
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