Color Transforms - Revision history

Patapom at 14:51, 5 January 2017

2017-01-05T14:51:28Z

Patapom at 17:22, 16 January 2012

2012-01-16T17:22:52Z

Patapom at 19:41, 4 January 2012

2012-01-04T19:41:28Z

Patapom at 19:40, 4 January 2012

2012-01-04T19:40:50Z

Patapom at 17:06, 3 January 2012

2012-01-03T17:06:50Z

Patapom at 16:55, 3 January 2012

2012-01-03T16:55:41Z

Patapom at 16:30, 3 January 2012

2012-01-03T16:30:08Z

Patapom at 16:28, 3 January 2012

2012-01-03T16:28:13Z

Patapom at 16:04, 3 January 2012

2012-01-03T16:04:08Z

Patapom at 15:56, 3 January 2012

2012-01-03T15:56:39Z

@@ Line 186: / Line 186: @@
 * Output:
 ** L* in [0,100]
-** a*, b* in [-?,?]
+** a*, b* in [-1,1]
   var_X = X / ref_X          // ref_X = 0.95047   Observer= 2°, Illuminant= D65
@@ Line 206: / Line 206: @@
 * Input:
 ** L* in [0,100]
-** a*, b* in [-?,?]
+** a*, b* in [-1,1]
 * Output: (Observer. = 2°, Illuminant = D65)
 ** X in [0, 0.95047]

← Older revision		Revision as of 17:22, 16 January 2012
Line 390:		Line 390:
	if ( B > 0.001953 ) B = B ^ ( 1 / 1.8 )		if ( B > 0.001953 ) B = B ^ ( 1 / 1.8 )
	else B = 16.0 * B		else B = 16.0 * B
		+
		+
		+	==RGB (in Radiance RGB) / XYZ==
		+	Radiance RGB is the default profile for Radiance files (*.HDR) and the chromaticities found in the [http://www.radiance-online.org/ source code] are:
		+	{\|style="border-collapse: separate; border-spacing: 0; border-width: 1px; border-style: solid; border-color: #000; padding: 0"
		+	\|-
		+	!style="border-style: solid; border-width: 0 1px 1px 0"\| color
		+	!style="border-style: solid; border-width: 0 1px 1px 0"\| x
		+	!style="border-style: solid; border-width: 0 0 1px 0"\| y
		+	\|-
		+	!style="border-style: solid; border-width: 0 1px 1px 0"\| Red
		+	\|style="border-style: solid; border-width: 0 1px 1px 0"\| 0.64
		+	\|style="border-style: solid; border-width: 0 0 1px 0"\| 0.33
		+	\|-
		+	!style="border-style: solid; border-width: 0 1px 1px 0"\| Green
		+	\|style="border-style: solid; border-width: 0 1px 1px 0"\| 0.29
		+	\|style="border-style: solid; border-width: 0 0 1px 0"\| 0.6
		+	\|-
		+	!style="border-style: solid; border-width: 0 1px 1px 0"\| Blue
		+	\|style="border-style: solid; border-width: 0 1px 1px 0"\| 0.15
		+	\|style="border-style: solid; border-width: 0 0 1px 0"\| 0.06
		+	\|-
		+	!style="border-style: solid; border-width: 0 1px 0 0"\| White
		+	\|style="border-style: solid; border-width: 0 1px 0 0"\| 0.3333
		+	\|style="border-style: solid; border-width: 0 0 0 0"\| 0.3333
		+	\|}
		+
		+	===RGB → XYZ===
		+	* Input: RGB in [0,1]
		+	* Output:
		+	** X in [0, 0.96421]
		+	** Y in [0, 1.00000]
		+	** Z in [0, 0.82519]
		+
		+	X = 0.5141 * R + 0.3238 * G + 0.1619 * B
		+	Y = 0.2651 * R + 0.6701 * G + 0.0647 * B
		+	Z = 0.0241 * R + 0.1228 * G + 0.8530 * B
		+
		+	===XYZ → RGB===
		+	* Input:
		+	** X in [0, 0.96421]
		+	** Y in [0, 1.00000]
		+	** Z in [0, 0.82519]
		+	* Output: RGB in [0,1]
		+
		+	R = 2.5653 * X - 1.1668 * Y - 0.3984 * Z
		+	G = -1.0221 * X + 1.9783 * Y + 0.0438 * Z
		+	B = 0.0747 * X - 0.2519 * Y + 1.1772 * Z

@@ Line 463: / Line 463: @@
 ==Custom ICC Profiles==
-Decoding true ICC profiles is a little ''over the top'' for our purpose so I won't be discussing full custom profiles here although you can read the [http://www.color.org/specification/ICC1v43_2010-12.pdf ICC Profile specs]] if you like.
+Decoding true ICC profiles is a little ''over the top'' for our purpose so I won't be discussing full custom profiles here although you can read the [http://www.color.org/specification/ICC1v43_2010-12.pdf ICC Profile specs] if you like.
 Also, if you really need a complete [[Color_Profile#Color_Management|CMS]], you should download the excellent [http://www.littlecms.com/ Little CMS] by Marti Maria.

← Older revision		Revision as of 19:40, 4 January 2012
Line 461:		Line 461:


−	==Custom Profiles==	+	==Custom ICC Profiles==
−	~~LUT~~

		+	Decoding true ICC profiles is a little ''over the top'' for our purpose so I won't be discussing full custom profiles here although you can read the [http://www.color.org/specification/ICC1v43_2010-12.pdf ICC Profile specs]] if you like.

−	~~==The ICC~~/~~ICM file format==~~	+	Also, if you really need a complete [[Color_Profile#Color_Management\|CMS]], you should download the excellent [http://www.littlecms.com/ Little CMS] by Marti Maria.
−
−
−
−	~~=HDR Images=~~

@@ Line 400: / Line 400: @@
-First of all, let's enumerate what we know:
+First of all, remembering our basic [[Colorimetry#CIE_xyY|CIEXYZ and CIExyY conversions]], let's enumerate what we know:
 :<math>xyz_R = \frac{XYZ_R}{X_R+Y_R+Z_R} = \frac{XYZ_R}{\Sigma_R}</math> from the chromaticities for Red
 :<math>xyz_G = \frac{XYZ_G}{X_G+Y_G+Z_G} = \frac{XYZ_G}{\Sigma_G}</math> from the chromaticities for Green

← Older revision		Revision as of 16:30, 3 January 2012
Line 458:		Line 458:
	</math>		</math>

−	we finally obtain <math>M_{XYZ}</math> that converts a RGB color into an XYZ color (you ~~obviously~~ use the inverse <math>M_{XYZ}^{-1}</math> to convert from XYZ back into RGB.	+	we finally obtain <math>M_{XYZ}</math> that converts a RGB color into an XYZ color (obviously, you need to use the inverse <math>M_{XYZ}^{-1}</math> to convert from XYZ back into RGB).

@@ Line 408: / Line 408: @@
 :<math>XYZ_W</math> (since we have a completely defined <math>xyY_W</math>, we can thus easily convert to <math>XYZ_W</math>, see [[Colorimetry#CIE_XYZ|CIE XYZ color space]])
-We are looking for <math>M_{XYZ}</math> so that:
+Note that we ''don't know'' the <math>XYZ_R</math>, <math>XYZ_G</math> and <math>XYZ_B</math> vectors.
 :<math>
 XYZ = RGB . M_{XYZ} = RGB .

@@ Line 444: / Line 444: @@
 we thus obtain <math>\Sigma_{RGB}</math> and since:
 :<math>
-M_{XYZ} =
+\begin{bmatrix}
 \begin{bmatrix}
 XYZ_R \\
 XYZ_G \\
 XYZ_B
-\end{bmatrix} =
+\end{bmatrix} =  M_{XYZ}
 </math>