On 11/24/2016 8:28 PM, Mike Horvath wrote:
> I've attached the final shape, with the outside sRGB bits trimmed off.
>
> Mike

For comparison, here is the same image with the corner bits left in.

Mike

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Attachments:
Download 'cielch_color_solid_cylinder_isosurface.png' (24 KB)

Preview of image 'cielch_color_solid_cylinder_isosurface.png'

On 11/24/2016 8:33 PM, clipka wrote:
> Don't try to go via that route; it won't work with the approach I've
> described.
>
> Instead, in the function pipeline, insert a function to explicitly
> convert from sRGB to RGB:
>
>     3D cartesian -> Lch -> sRGB -> RGB -> "distance"
>
>     3D cartesian -> Lch -> sRGB -> RGB -> pigments
>

Do you have a function to convert between sRGB and RGB? One was not 
included with ColorMine AFAIK.

Mike

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Am 25.11.2016 um 02:59 schrieb Mike Horvath:
> On 11/24/2016 8:33 PM, clipka wrote:
>> Don't try to go via that route; it won't work with the approach I've
>> described.
>>
>> Instead, in the function pipeline, insert a function to explicitly
>> convert from sRGB to RGB:
>>
>>     3D cartesian -> Lch -> sRGB -> RGB -> "distance"
>>
>>     3D cartesian -> Lch -> sRGB -> RGB -> pigments
>>
> 
> Do you have a function to convert between sRGB and RGB? One was not
> included with ColorMine AFAIK.

No ready-made function; you'll need to piece things together from e.g.
https://en.wikipedia.org/wiki/SRGB.

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Am 25.11.2016 um 02:33 schrieb clipka:

> Instead, in the function pipeline, insert a function to explicitly
> convert from sRGB to RGB:
> 
>     3D cartesian -> Lch -> sRGB -> RGB -> "distance"
> 
>     3D cartesian -> Lch -> sRGB -> RGB -> pigments

I forgot: You won't necessarily need the sRGB->RGB step for the
"distance" function, as sRGB channel values of 0 and 1 map to RGB
channel values of 0 and 1, respectively.

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On 11/24/2016 9:11 PM, clipka wrote:
> Am 25.11.2016 um 02:59 schrieb Mike Horvath:
>> On 11/24/2016 8:33 PM, clipka wrote:
>>> Don't try to go via that route; it won't work with the approach I've
>>> described.
>>>
>>> Instead, in the function pipeline, insert a function to explicitly
>>> convert from sRGB to RGB:
>>>
>>>     3D cartesian -> Lch -> sRGB -> RGB -> "distance"
>>>
>>>     3D cartesian -> Lch -> sRGB -> RGB -> pigments
>>>
>>
>> Do you have a function to convert between sRGB and RGB? One was not
>> included with ColorMine AFAIK.
>
> No ready-made function; you'll need to piece things together from e.g.
> https://en.wikipedia.org/wiki/SRGB.
>

I am looking at the "The reverse transformation" section. Do I just need 
to use the C_linear function?


Mike

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Am 25.11.2016 um 03:31 schrieb Mike Horvath:
> On 11/24/2016 9:11 PM, clipka wrote:
>> Am 25.11.2016 um 02:59 schrieb Mike Horvath:
>>> On 11/24/2016 8:33 PM, clipka wrote:
>>>> Don't try to go via that route; it won't work with the approach I've
>>>> described.
>>>>
>>>> Instead, in the function pipeline, insert a function to explicitly
>>>> convert from sRGB to RGB:
>>>>
>>>>     3D cartesian -> Lch -> sRGB -> RGB -> "distance"
>>>>
>>>>     3D cartesian -> Lch -> sRGB -> RGB -> pigments
>>>>
>>>
>>> Do you have a function to convert between sRGB and RGB? One was not
>>> included with ColorMine AFAIK.
>>
>> No ready-made function; you'll need to piece things together from e.g.
>> https://en.wikipedia.org/wiki/SRGB.
>>
> 
> I am looking at the "The reverse transformation" section. Do I just need
> to use the C_linear function?

Yup, that's the one.

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On 11/24/2016 9:54 PM, clipka wrote:
> Am 25.11.2016 um 03:31 schrieb Mike Horvath:
>> On 11/24/2016 9:11 PM, clipka wrote:
>>> No ready-made function; you'll need to piece things together from e.g.
>>> https://en.wikipedia.org/wiki/SRGB.
>>>
>>
>> I am looking at the "The reverse transformation" section. Do I just need
>> to use the C_linear function?
>
> Yup, that's the one.
>
>

Okay, I will try that.

Mike

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>> May I ask the stupid question, "why not"?
>>
>> I would expect the Lch colour space to encompass all the RGB colour
>> space, so the boundaries of the latter should be sufficient to bound the
>> shape.
>>
>> My guess is that the issues you see with the shape are due to bogosities
>> in your colour conversion functions.
>>
>
> L, C and H are supposed to form a cylinder. There are some very small
> sRGB bits poking outside of the cylinder. I guess I could show the bits
> as well, as long as I explain what they are.

If sRGB is poking out of your cylinder, then Adobe RGB is going to poke 
out even more, and the entire human visual range is going to be much 
larger. Are you sure you've got the radius of your cylinder correct to 
match your colour calculations? Also it would be surprising to me if the 
human visual range came out exactly as a cylinder (after a brief glance 
of the maths involved), are you sure about this?

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On 11/28/2016 3:23 AM, scott wrote:
>>> May I ask the stupid question, "why not"?
>>>
>>> I would expect the Lch colour space to encompass all the RGB colour
>>> space, so the boundaries of the latter should be sufficient to bound the
>>> shape.
>>>
>>> My guess is that the issues you see with the shape are due to bogosities
>>> in your colour conversion functions.
>>>
>>
>> L, C and H are supposed to form a cylinder. There are some very small
>> sRGB bits poking outside of the cylinder. I guess I could show the bits
>> as well, as long as I explain what they are.
>
> If sRGB is poking out of your cylinder, then Adobe RGB is going to poke
> out even more, and the entire human visual range is going to be much
> larger. Are you sure you've got the radius of your cylinder correct to
> match your colour calculations? Also it would be surprising to me if the
> human visual range came out exactly as a cylinder (after a brief glance
> of the maths involved), are you sure about this?
>

Yeah, I explain the mistake I made in this thread:

http://news.povray.org/583bd889%241%40news.povray.org

Mike

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On 11/28/2016 3:23 AM, scott wrote:
> Also it would be surprising to me if the
> human visual range came out exactly as a cylinder (after a brief glance
> of the maths involved), are you sure about this?
>

The human visual range has a very irregular shape.

https://en.wikipedia.org/wiki/File:Cie_Chart_with_sRGB_gamut_by_spigget.png

There's a lot of blank empty space around it in every color space. (The 
one in the picture is called CIExyY I think.

I would like to learn how to plot this irregular shape in the near future.

Mike

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