update included sample code

Author: svgeesus

css-color-4/Overview.bs

@@ -3043,7 +3043,7 @@ Default Style Rules</h2>
 <em>This section is not normative.</em>
 
 <pre class="lang-javascript">
-	<!-- imported 25 Feb 2019-->
+	<!-- imported 4 Mar  2019-->
 	// sRGB-related functions
 
 	function lin_sRGB(RGB) {
@@ -3143,16 +3143,26 @@ Default Style Rules</h2>
 	function lin_ProPhoto(RGB) {
 		// convert an array of ProPhotoRGB values in the range 0.0 - 1.0
 		// to linear light (un-companded) form.
+		// Transfer curve is gamma 1.0 with a small linear portion
 		return RGB.map(function (val) {
-		  return Math.pow(val, 1.8);
+			if (val < 0.031248) {
+				return val / 16;
+			}
+
+			return Math.pow(val, 1.8);
 		});
 	}
 
 	function gam_ProPhoto(RGB) {
 		// convert an array of linear-light ProPhotoRGB  in the range 0.0-1.0
 		// to gamma corrected form
+		// Transfer curve is gamma 1.0 with a small linear portion
 		return RGB.map(function (val) {
-			return Math.pow(val, 1/1.8);
+			if (val > 0.001953) {
+				return Math.pow(val, 1/1.8);
+			}
+
+			return 16 * val;
 		});
 	}
 
@@ -3172,9 +3182,9 @@ Default Style Rules</h2>
 	function XYZ_to_lin_ProPhoto(XYZ) {
 		// convert XYZ to linear-light ProPhotoRGB
 		var M = Math.matrix([
-		  [  1.3457989731028281,  -0.25558010007997534,  -0.05110628506753401 ],
-		  [ -0.5446224939028347,   1.5082327413132781,    0.02053603239147973 ],
-		  [  0.0,                  0.0,                   1.2119675456389454  ]
+			[  1.3457989731028281,  -0.25558010007997534,  -0.05110628506753401 ],
+			[ -0.5446224939028347,   1.5082327413132781,    0.02053603239147973 ],
+			[  0.0,                  0.0,                   1.2119675456389454  ]
 		]);
 
 		return Math.multiply(M, XYZ).valueOf();
@@ -3186,7 +3196,7 @@ Default Style Rules</h2>
 		// convert an array of a98rgb values in the range 0.0 - 1.0
 		// to linear light (un-companded) form.
 		return RGB.map(function (val) {
-		  return Math.pow(val, 563/256);
+			return Math.pow(val, 563/256);
 		});
 	}
 
@@ -3204,7 +3214,7 @@ Default Style Rules</h2>
 		// http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html
 		var M = Math.matrix([
 		[ 0.5766690429101305,   0.1855582379065463,   0.1882286462349947  ],
-		[ 0.29734497525053605,  0.6273635662554661,   0.07529145849399788 ]​,
+		[ 0.29734497525053605,  0.6273635662554661,   0.07529145849399788 ],
 		[ 0.02703136138641234,  0.07068885253582723,  0.9913375368376388  ]
 		]);
 
@@ -3215,8 +3225,8 @@ Default Style Rules</h2>
 		// convert XYZ to linear-light ProPhotoRGB
 		var M = Math.matrix([
 		[  2.0415879038107465,    -0.5650069742788596,   -0.34473135077832956 ],
-	​	 [ -0.9692436362808795,     1.8759675015077202,    0.04155505740717557 ],
-	​	 [  0.013444280632031142,  -0.11836239223101838,   1.0151749943912054  ]
+		[ -0.9692436362808795,     1.8759675015077202,    0.04155505740717557 ],
+		[  0.013444280632031142,  -0.11836239223101838,   1.0151749943912054  ]
 		]);
 
 		return Math.multiply(M, XYZ).valueOf();