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Am 25.11.2016 um 01:50 schrieb Mike Horvath:
> On 11/24/2016 6:43 PM, clipka wrote:
>> Am 24.11.2016 um 23:56 schrieb Mike Horvath:
>>
>>> Okay, the problem is that I want to use sRGB instead of RGB in the
>>> pigments. However, it seems to not be possible to multiply the sRGB
>>> colors and then average them like you can with regular RGB. Or is there
>>> a way to get this to work?
>>
>> Don't use sRGB when mucking around with colour spaces, unless you know
>> /exactly/ what you are doing. Colour space experts are smart enough to
>> specify colours in terms of linear light intensity, or otherwise
>> explicitly inform the readers.
>>
>
> The functions output sRGB colors with Illuminant = D65 and Observer = 2°
> (1931) according to one of the conversion websites that uses these
> formulas.
>
> I'd like the POV code to use sRGB as well.
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
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Am 25.11.2016 um 01:47 schrieb Mike Horvath:
> Thank you clipka! Everything is working perfectly now! Part of the
> problem was a bug in my conversion functions. Once I fixed it, I started
> getting the correct results.
>
> Do you mind if I put a LGPL license on the code an upload it to Wikipedia?
Feel free to do so.
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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
Post a reply to this message
Attachments:
Download 'cielch_color_solid_cylinder_isosurface.png' (24 KB)
Preview of image 'cielch_color_solid_cylinder_isosurface.png'
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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
Post a reply to this message
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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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