From b62e56d95265dfba1a848c8903093f402883dcab Mon Sep 17 00:00:00 2001
From: Cameron McCormack <cam@mcc.id.au>
Date: Wed, 3 Jun 2020 10:37:57 +1000
Subject: [PATCH] Expose image orientation metadata on HTMLImageElement

Fixes #5602.
---
 source | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 80 insertions(+), 1 deletion(-)

diff --git a/source b/source
index 92a08babf1b..d0be48f9f92 100644
--- a/source
+++ b/source
@@ -25882,6 +25882,8 @@ interface <dfn>HTMLImageElement</dfn> : <span>HTMLElement</span> {
   [<span>CEReactions</span>] attribute unsigned long <span data-x="dom-img-height">height</span>;
   readonly attribute unsigned long <span data-x="dom-img-naturalWidth">naturalWidth</span>;
   readonly attribute unsigned long <span data-x="dom-img-naturalHeight">naturalHeight</span>;
+  readonly attribute unsigned long <span data-x="dom-img-intrinsicOrientationAngle">intrinsicOrientationAngle</span>;
+  readonly attribute boolean <span data-x="dom-img-intrinsicOrientationFlip">intrinsicOrientationFlip</span>;
   readonly attribute boolean <span data-x="dom-img-complete">complete</span>;
   readonly attribute USVString <span data-x="dom-img-currentSrc">currentSrc</span>;
   [<span>CEReactions</span>] attribute DOMString <span data-x="dom-img-referrerPolicy">referrerPolicy</span>;
@@ -26216,6 +26218,14 @@ interface <dfn>HTMLImageElement</dfn> : <span>HTMLElement</span> {
     or zero if the dimensions are not known.</p>
    </dd>
 
+   <dt><var>image</var> . <code subdfn data-x="dom-img-intrinsicOrientationAngle">intrinsicOrientationAngle</code></dt>
+   <dt><var>image</var> . <code subdfn data-x="dom-img-intrinsicOrientationFlip">intrinsicOrientationFlip</code></dt>
+
+   <dd>
+    <p>These attributes return the orientation metadata of the image, or zero and false if there is
+    none.</p>
+   </dd>
+
    <dt><var>image</var> . <code subdfn data-x="dom-img-complete">complete</code></dt>
 
    <dd>
@@ -26278,6 +26288,16 @@ interface <dfn>HTMLImageElement</dfn> : <span>HTMLElement</span> {
   any rotation needed to correctly orient the image, regardless of the value of the
   <span>'image-orientation'</span> property.</p>
 
+  <p>The IDL attribute <dfn
+  data-x="dom-img-intrinsicOrientationAngle"><code>intrinsicOrientationAngle</code></dfn> must
+  return the angle of the <span data-x="img-req-data">image data</span>'s <span>intrinsic
+  orientation</span>.</p>
+
+  <p>The IDL attribute <dfn
+  data-x="dom-img-intrinsicOrientationFlip"><code>intrinsicOrientationFlip</code></dfn> must
+  return true if the <span data-x="img-req-data">image data</span>'s <span>intrinsic
+  orientation</span> applies the optional horizontal flip, and false otherwise.</p>
+
   <p>The IDL attribute <dfn data-x="dom-img-complete"><code>complete</code></dfn> must return true if
   any of the following conditions is true:</p>
 
@@ -27265,7 +27285,8 @@ was an English &lt;a href="/wiki/Music_hall">music hall&lt;/a> singer, ...</code
   The <span>pending request</span> is initially set to null.</p>
 
   <p>An <dfn>image request</dfn> has a <dfn data-x="img-req-state">state</dfn>, <dfn
-  data-x="img-req-url">current URL</dfn>, and <dfn data-x="img-req-data">image data</dfn>.</p>
+  data-x="img-req-url">current URL</dfn>, <dfn data-x="img-req-data">image data</dfn>, and
+  <dfn data-x="img-req-orientation">orientation</dfn>.</p>
 
   <p>An <span>image request</span>'s <span data-x="img-req-state">state</span> is one of the
   following:</p>
@@ -27296,6 +27317,64 @@ was an English &lt;a href="/wiki/Music_hall">music hall&lt;/a> singer, ...</code
   <p>An <span>image request</span>'s <span data-x="img-req-data">image data</span> is the decoded
   image data.</p>
 
+  <p>An <span>image request</span>'s <span data-x="img-req-data">image data</span> has an associated
+  <dfn>intrinsic orientation</dfn>, which is the orthogonal transformation that was applied to the
+  raw data in the image during its decoding. The transformation consists of a rotation of 0, 90,
+  180, or 270 degrees, followed by an optional horizontal flip. If no transformation was applied,
+  the <span>intrinsic orientation</span> is considered to be 0 degrees with no horizontal flip.</p>
+
+  <div class="note">
+
+   <p>This transformation is the one that is automatically applied when the
+   <span>'image-orientation'</span> property is set to 'from-image'.</p>
+
+   <p>For JPEG images, the <span>intrinsic orientation</span> is the orientation specified by the
+   EXIF metadata Orientation tag. Orientation tag values correspond to <span>intrinsic
+   orientation</span> values as follows:</p>
+
+   <table>
+    <thead>
+     <tr>
+      <th>Tag value
+      <th>Angle
+      <th>Horizontal flip
+    <tbody>
+     <tr>
+       <td>1
+       <td>0&deg;
+       <td>no
+     <tr>
+       <td>2
+       <td>0&deg;
+       <td>yes
+     <tr>
+       <td>3
+       <td>180&deg;
+       <td>no
+     <tr>
+       <td>4
+       <td>180&deg;
+       <td>yes
+     <tr>
+       <td>5
+       <td>90&deg;
+       <td>yes
+     <tr>
+       <td>6
+       <td>90&deg;
+       <td>no
+     <tr>
+       <td>7
+       <td>270&deg;
+       <td>yes
+     <tr>
+       <td>8
+       <td>270&deg;
+       <td>no
+   </table>
+
+  </div>
+
   <p>When an <span>image request</span>'s <span data-x="img-req-state">state</span> is either <span
   data-x="img-inc">partially available</span> or <span data-x="img-all">completely available</span>,
   the <span>image request</span> is said to be <dfn data-x="img-available">available</dfn>.</p>