Update documents (#6)

rmagick/rmagick#1398

Author: Watson1978

draw.html

@@ -652,8 +652,8 @@ <h4>Description</h4>
     image.  Metrics are derived from either the <a href="#attributes">
     annotate attributes</a> or from the <a href="info.html">image
     info attributes</a>, but not from any drawing primitive methods.
-    The <code>get_multiline_type_metrics</code> method is the same as 
-    <code>get_type_metrics</code>, except the former returns the 
+    The <code>get_multiline_type_metrics</code> method is the same as
+    <code>get_type_metrics</code>, except the former returns the
     maximum height and width for multiple lines of text. (Text lines
     are separated by "\n" characters.)</p>
 
@@ -2650,8 +2650,8 @@ <h4>Description</h4>
     "#font_weight">font_weight</a> methods. Specify the text
     attributes with the <a href="#text_align">text_align</a>,
     <a href="#text_anchor">text_anchor</a>, <a href=
-    "text_antialias">text_antialias</a>, and <a href=
-    "text_undercolor">text_undercolor</a> methods.</p>
+    "#text_antialias">text_antialias</a>, and <a href=
+    "#text_undercolor">text_undercolor</a> methods.</p>
 
     <p>Generally it is a good idea to surround the text string with
     quotes (""), apostrophes (''), or braces ({}). If the text

ilist.html

@@ -947,7 +947,7 @@ <h4>Description</h4>
 
     <p>Applies the specified mathematical expression to the input
     images. This method corresponds to ImageMagick's <a href=
-    "http://redux.imagemagick.org/script/fx.php">-fx</a>
+    "https://imagemagick.org/script/fx.php">-fx</a>
     operator.</p>
 
     <h4>Arguments</h4>
@@ -1696,7 +1696,7 @@ <h4>Arguments</h4>
 
       <dd>A <a href="constants.html#DitherMethod">DitherMethod</a>
       value. See the documentation for the <a href=
-      "http://redux.imagemagick.org/script/command-line-options.php#dither">
+      "https://imagemagick.org/script/command-line-options.php#dither">
       ImageMagick -dither option</a> for more information.</dd>
 
       <dt>tree_depth</dt>

image2.html

@@ -3578,7 +3578,7 @@ <h4>Arguments</h4>
     number of levels per color channel</span> immediately following
     the <span class="arg">threshold_map</span>, separated by a
     comma. See the documentation for <a href=
-    "http://redux.imagemagick.org/script/command-line-options.php#ordered-dither">
+    "https://imagemagick.org/script/command-line-options.php#ordered-dither">
     ImageMagick's -ordered-dither option</a> for more
     information.</p>
 

imageattrs.html

@@ -1363,7 +1363,7 @@ <h4>Returns</h4>
     <h4>See also</h4>
 
     <p><a href="#x_resolution">x_resolution</a>, <a href=
-    "y_resolution">y_resolution</a></p>
+    "#y_resolution">y_resolution</a></p>
   </div>
 
   <div class="sig">

magick.html

@@ -422,7 +422,7 @@ <h4>Log configuration</h4>
 
     <p>Magick logging is configured with the log.xml file in
     Magick's config directory. See <a href=
-    "http://redux.imagemagick.org/script/resources.php">Resources</a>
+    "https://imagemagick.org/script/resources.php">Resources</a>
     in the ImageMagick documentation for more information.</p>
 
     <p>Use this command to find out about the current log

optequiv.html

@@ -205,7 +205,7 @@ <h3>Introduction</h3>
         "draw.html#text_antialias">text_antialias</a>(<code>true</code>)
         (for drawing)<br />
         Draw#<a href=
-        "Draw#text_antialias_eq">text_antialias=</a><code>true</code>
+        "draw.html#text_antialias_eq">text_antialias=</a><code>true</code>
         (for annotation)</td>
       </tr>
 
@@ -929,7 +929,7 @@ <h3>Introduction</h3>
         <td>-gamma <em>red_gamma,green_gamma,blue_gamma</em></td>
 
         <td>Image#<a href=
-        "imageattrs.htlm#gamma_correct">gamma_correct</a>(<em>red_gamma</em>[,
+        "image2.html#gamma_correct">gamma_correct</a>(<em>red_gamma</em>[,
         <em>green_gamma</em>[, <em>blue_gamma</em>]])</td>
       </tr>
 

usage.html

@@ -1586,7 +1586,7 @@ <h5 id="footnotes">Footnotes</h5>
     and view it with a separate image viewer.</p>
 
     <p id="rubygems"><span class="sup">2</span>If you installed
-    RMagick using <a href="http://docs.rubygems.org/">Rubygems</a>
+    RMagick using <a href="https://rubygems.org/">Rubygems</a>
     you must set up the RubyGems environment before using RMagick.
     You can do one of</p>
 
@@ -1600,10 +1600,6 @@ <h5 id="footnotes">Footnotes</h5>
       variable</li>
     </ol>
 
-    <p>See the RubyGems <a href=
-    "http://docs.rubygems.org/read/chapter/3#page70">doc</a> for
-    more information.</p>
-
     <p id="degrees"><span class="sup">3</span>The rotation
     attributes <code>rx</code> and <code>ry</code> in the <a href=
     "struct.html#AffineMatrix"><code>AffineMatrix</code></a> class