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AI 148470: add documentation about aapt image optimization

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BUG=1735176

Automated import of CL 148470
This commit is contained in:
Scott Main
2009-05-07 11:59:14 -07:00
committed by The Android Open Source Project
parent 1f8059f19f
commit 9b825aa0ee
2 changed files with 26 additions and 8 deletions
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15
docs/html/guide/topics/graphics/2d-graphics.jd
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@@ -10,8 +10,8 @@ parent.link=index.html
<ol>
<li><a href="#drawables">Drawables</a>
<ol>
<li><a href="#drawable-images">Creating from resource images</a></li>
<li><a href="#drawable-xml">Creating from resource XML</a></li>
<li><a href="#drawables-from-images">Creating from resource images</a></li>
<li><a href="#drawables-from-xml">Creating from resource XML</a></li>
</ol>
</li>
<li><a href="#shape-drawable">ShapeDrawable</a></li>
@@ -59,6 +59,15 @@ From there, you can reference it from your code or your XML layout.
Either way, it is referred using a resource ID, which is the file name without the file type
extension (E.g., <code>my_image.png</code> is referenced as <var>my_image</var>).</p>
<p class="note"><strong>Note:</strong> Image resources placed in <code>res/drawable/</code> may be
automatically optimized with lossless image compression by the
<a href="{@docRoot}guide/developing/tools/aapt.html">aapt</a> tool. For example, a true-color PNG that does
not require more than 256 colors may be converted to an 8-bit PNG with a color palette. This
will result in an image of equal quality but which requires less memory. So be aware that the
image binaries placed in this directory can change during the build. If you plan on reading
an image as a bit stream in order to convert it to a bitmap, put your images in the <code>res/raw/</code>
folder instead, where they will not be optimized.</p>
<h4>Example code</h4>
<p>The following code snippet demonstrates how to build an {@link android.widget.ImageView} that uses an image
from drawable resources and add it to the layout.</p>
@@ -90,7 +99,7 @@ Resources res = mContext.getResources();
Drawable myImage = res.getDrawable(R.drawable.my_image);
</pre>
<p class="caution"><strong>Caution:</strong> Each unique resource in your project can maintain only one
<p class="warning"><strong>Note:</strong> Each unique resource in your project can maintain only one
state, no matter how many different objects you may instantiate for it. For example, if you instantiate two
Drawable objects from the same image resource, then change a property (such as the alpha) for one of the
Drawables, then it will also affect the other. So when dealing with multiple instances of an image resource,

19
docs/html/guide/topics/resources/resources-i18n.jd
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@@ -111,21 +111,30 @@ the containing file.</p>
<td><code>res/drawable/</code></td>
<td><p>.png, .9.png, .jpg files that are compiled into the following
Drawable resource subtypes:</p>
<p>To get a resource of this type, use <code>Resource.getDrawable(<em>id</em>)</code>
<ul>
<ul class="nolist">
<li><a href="available-resources.html#imagefileresources">bitmap files</a></li>
<li><a href="available-resources.html#ninepatch">9-patches (resizable bitmaps)</a></li>
</ul></td>
</ul>
<p>To get a resource of this type, use <code>mContext.getResources().getDrawable(R.drawable.<em>imageId</em>)</code></p>
<p class="note"><strong>Note:</strong> Image resources placed in here may
be automatically optimized with lossless image compression by the
<a href="{@docRoot}guide/developing/tools/aapt.html">aapt</a> tool. For example, a true-color PNG
that does not require more than 256 colors may be converted to an 8-bit PNG with a color palette.
This will result in an image of equal quality but which requires less memory. So be aware that the
image binaries placed in this directory can change during the build. If you plan on reading
an image as a bit stream in order to convert it to a bitmap, put your images in the
<code>res/raw/</code> folder instead, where they will not be optimized.</p>
</td>
</tr>
<tr>
<td><code>res/layout/</code></td>
<td>XML files that are compiled into screen layouts (or part of a screen).
See <a href="{@docRoot}guide/topics/ui/declaring-layout.html">Declaring Layout</a></td>
See <a href="{@docRoot}guide/topics/ui/declaring-layout.html">Declaring Layout</a>.</td>
</tr>
<tr>
<td><code>res/values/</code></td>
<td><p>XML files that can be compiled into many kinds of resource.</p>
<p class="note"><strong>Note:</strong> unlike the other res/ folders, this one
<p class="note"><strong>Note:</strong> Unlike the other res/ folders, this one
can hold any number of files that hold descriptions of resources to create
rather than the resources themselves. The XML element types control
where these resources are placed under the R class.</p>