Hi Ian,
Here are a couple of references that deal with implementing Hue-Rotate:
https://beesbuzz.biz/code/hsv_color_transforms.php
http://crawlingrobotfortress.blogspot.ca/2013/06/optimizing-hue-rotation-operator.html
The basic idea is you have an image in the HSV
<https://en.wikipedia.org/wiki/HSL_and_HSV> colour space, and you change
the increment the Hue of each pixel by some amount. This has the effect of
"rotating" the hue of the image as a whole.
It is a fairly common transform in most graphical programs (like GIMP or
Photoshop).
Torben
On Fri, Jul 14, 2017 at 1:59 PM, Jody Garnett <jody.garn...@gmail.com>
wrote:
> Thanks for the correction Andrea, this would be a raster-to-raster
> rendering transform, or a new normalization algorithm.
>
> Ian - Hue rotate is used when an image has been produced with
> complementary colours (in a colour wheel sense). If you can image spinning
> the color wheel while leaving the everything in the same relative position.
> It is used in video games for example to reuse graphic assets. Torben had a
> good reference if we ask him.
>
>
>
>
> --
> Jody Garnett
>
> On 14 July 2017 at 13:18, Andrea Aime <andrea.a...@geo-solutions.it>
> wrote:
>
>> Ian,
>> Jody is calling them geometry transformations, but he really means
>> rendering transformations (geometry transformation
>> is the act of applying a function inside the geometry tag for the current
>> vector feature, has nothing to do with rasters):
>>
>> http://docs.geoserver.org/stable/en/user/styling/sld/extensi
>> ons/geometry-transformations.html
>> http://docs.geoserver.org/stable/en/user/styling/sld/extensi
>> ons/rendering-transform.html
>>
>> Cheers
>> Andrea
>>
>> On Fri, Jul 14, 2017 at 9:25 PM, Ian Turton <ijtur...@gmail.com> wrote:
>>
>>> Could you please expand on what hue rotate does? I'm not sure if I
>>> understand it well enough to decide if it is an image operation or a
>>> geometry operation.
>>>
>>> Ian
>>>
>>> On 14 Jul 2017 18:15, "Jody Garnett" <jody.garn...@gmail.com> wrote:
>>>
>>> ShadedRelief was the only other thing I could think of, in SLD spec
>>> directly.
>>>
>>> We also have our geoserver specific extension for geometry
>>> transformations. We have to ask someone here if that can be used to
>>> introduce the colorSpace operation
>>> <http://iihm.imag.fr/Docs/java/jai1_0guide/Color.doc.html#51551> to HSV
>>> and then a bandcombine operation
>>> <http://iihm.imag.fr/Docs/java/jai1_0guide/Color.doc.html#51591> for
>>> the color rotation in an efficient manner for rendering.
>>>
>>> --
>>> Jody Garnett
>>>
>>> On 14 July 2017 at 09:04, John Schulz <jsch...@boundlessgeo.com> wrote:
>>>
>>>> I looking through what additional functionality I am looking for, I
>>>> think it might be appropriate to add in a ColorEnhancement element of
>>>> sorts, to include algorithms for HueRotate and Saturation. I seems like a
>>>> lot of my work would overlap with what is already in ContrastEnhancement
>>>> and not sure how the additional efforts would payout.
>>>>
>>>> @Jody - you did mention that it might be better to implement in a
>>>> similar fashion of ShadedRelief, which would entail a new element in the
>>>> RasterLayer anyway - thoughts?
>>>>
>>>> John Schulz
>>>>
>>>> On Fri, Jul 14, 2017 at 9:17 AM, Jody Garnett <jody.garn...@gmail.com>
>>>> wrote:
>>>>
>>>>> Ian with respect to exposing new methods to the SLD, do you think Hue
>>>>> Rotate could be added as a new Color Normalization algorithm?
>>>>>
>>>>> The only other example I could think of would be as a geometry
>>>>> transformation, both options kind of make sense so I was not sure what to
>>>>> recommend.
>>>>>
>>>>> --
>>>>> Jody Garnett
>>>>>
>>>>> On 14 July 2017 at 00:47, Ian Turton <ijtur...@gmail.com> wrote:
>>>>>
>>>>>> Hi John,
>>>>>>
>>>>>> I'm not sure I'm necessarily the right person to ask about this as
>>>>>> all I did was expose the new methods to the SLD so that people could make
>>>>>> use of the new functionality. The actual code to make changes to the
>>>>>> raster
>>>>>> was writen long before I was there - https://github.com/geotools/
>>>>>> geotools/blame/master/modules/library/render/src/main/java/o
>>>>>> rg/geotools/renderer/lite/gridcoverage2d/ContrastEnhancementNode.java
>>>>>>
>>>>>> Hope that helps, if not feel free to continue to ask questions on
>>>>>> this list. Though I warn you a lot of us are travelling this week for
>>>>>> FOSS4GE and then building up to FOSS4G so there may be delays in
>>>>>> responding.
>>>>>>
>>>>>> Ian
>>>>>>
>>>>>> On 12 July 2017 at 19:29, John Schulz <jsch...@boundlessgeo.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Greeting Ian,
>>>>>>>
>>>>>>> I'm working on creating a hue rotate option for rasters processed in
>>>>>>> Geotools and with speaking with my team have come across your work with
>>>>>>> ContrastEnhancement and was hoping to get some insight into working with
>>>>>>> the normalization process and how it might be used in my endeavors.
>>>>>>>
>>>>>>> I look forward to hearing back on your thoughts.
>>>>>>>
>>>>>>> Cheers,
>>>>>>>
>>>>>>> John
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Ian Turton
>>>>>>
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>>>>>>
>>>>>
>>>>
>>>
>>>
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>>
>>
>> --
>>
>> Regards,
>>
>> Andrea Aime
>>
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