From f3d4d5bdccd4072984c0149ca449f0b7db94aa11 Mon Sep 17 00:00:00 2001 From: Chris Lilley Date: Fri, 1 Mar 2024 11:27:38 -0500 Subject: [PATCH 1/2] Recommend using extended transfer functions to handle negative values, fix #420 --- index.html | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/index.html b/index.html index 6b10132..cac99c0 100644 --- a/index.html +++ b/index.html @@ -3725,6 +3725,17 @@

cICP Coding-independent code points for video sig PNG format, it should be noted that this format is not part of the [[ITU-R-BT.709]] standard. +

If Video Full Range Flag is 0 + (a narrow-range image), recommended practice + is to define transfer functions + such as EOTF or inverse OETF + over the extended range, + so as to include negative values. + This is done as follows: +

+ + 
out = sign(in) * TransferFunction(abs(in))
+

The cICP chunk MUST come before the PLTE and IDAT chunks.

From 40e819baf9e0053da8762caeed6b7b315c5a81aa Mon Sep 17 00:00:00 2001 From: Chris Lilley Date: Fri, 1 Mar 2024 14:44:32 -0500 Subject: [PATCH 2/2] Define EOTF and OETF --- index.html | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/index.html b/index.html index cac99c0..89d6253 100644 --- a/index.html +++ b/index.html @@ -711,6 +711,12 @@

Terms, definitions, and abbreviated terms

vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen.
+
Electro-Optical Transfer Function
+
+ EOTF +
+
The transfer function between the electrical or digital domain and light energy. It defines the amount of light emitted by a display for a given input signal.
+
Least Significant Byte
LSB
@@ -724,6 +730,12 @@

Terms, definitions, and abbreviated terms

Most significant byte of a multi-byte value.
+ +
Opto-Electrical Transfer Function
+
+ OETF +
+
The transfer function between light energy and the electrical or digital domain. It defines the amount of light in a scene required to produce a given output signal.
@@ -3728,7 +3740,7 @@

cICP Coding-independent code points for video sig

If Video Full Range Flag is 0 (a narrow-range image), recommended practice is to define transfer functions - such as EOTF or inverse OETF + such as EOTF or inverse OETF over the extended range, so as to include negative values. This is done as follows: