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<title>GridSampler (ZXing 3.5.4 API)</title>
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<div class="sub-title"><span class="package-label-in-type">Package</span> <a href="package-summary.html">com.google.zxing.common</a></div>
<h1 title="Class GridSampler" class="title">Class GridSampler</h1>
</div>
<div class="inheritance" title="Inheritance Tree"><a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html" title="class or interface in java.lang" class="external-link">java.lang.Object</a>
<div class="inheritance">com.google.zxing.common.GridSampler</div>
</div>
<section class="class-description" id="class-description">
<dl class="notes">
<dt>Direct Known Subclasses:</dt>
<dd><code><a href="DefaultGridSampler.html" title="class in com.google.zxing.common">DefaultGridSampler</a></code></dd>
</dl>
<hr>
<div class="type-signature"><span class="modifiers">public abstract class </span><span class="element-name type-name-label">GridSampler</span>
<span class="extends-implements">extends <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html" title="class or interface in java.lang" class="external-link">Object</a></span></div>
<div class="block">Implementations of this class can, given locations of finder patterns for a QR code in an
image, sample the right points in the image to reconstruct the QR code, accounting for
perspective distortion. It is abstracted since it is relatively expensive and should be allowed
to take advantage of platform-specific optimized implementations, like Sun's Java Advanced
Imaging library, but which may not be available in other environments such as J2ME, and vice
versa.
The implementation used can be controlled by calling <a href="#setGridSampler(com.google.zxing.common.GridSampler)"><code>setGridSampler(GridSampler)</code></a>
with an instance of a class which implements this interface.</div>
<dl class="notes">
<dt>Author:</dt>
<dd>Sean Owen</dd>
</dl>
</section>
<section class="summary">
<ul class="summary-list">
<!-- ======== CONSTRUCTOR SUMMARY ======== -->
<li>
<section class="constructor-summary" id="constructor-summary">
<h2>Constructor Summary</h2>
<div class="caption"><span>Constructors</span></div>
<div class="summary-table two-column-summary">
<div class="table-header col-first">Constructor</div>
<div class="table-header col-last">Description</div>
<div class="col-constructor-name even-row-color"><code><a href="#%3Cinit%3E()" class="member-name-link">GridSampler</a>()</code></div>
<div class="col-last even-row-color"> </div>
</div>
</section>
</li>
<!-- ========== METHOD SUMMARY =========== -->
<li>
<section class="method-summary" id="method-summary">
<h2>Method Summary</h2>
<div id="method-summary-table">
<div class="table-tabs" role="tablist" aria-orientation="horizontal"><button id="method-summary-table-tab0" role="tab" aria-selected="true" aria-controls="method-summary-table.tabpanel" tabindex="0" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table', 3)" class="active-table-tab">All Methods</button><button id="method-summary-table-tab1" role="tab" aria-selected="false" aria-controls="method-summary-table.tabpanel" tabindex="-1" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table-tab1', 3)" class="table-tab">Static Methods</button><button id="method-summary-table-tab2" role="tab" aria-selected="false" aria-controls="method-summary-table.tabpanel" tabindex="-1" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table-tab2', 3)" class="table-tab">Instance Methods</button><button id="method-summary-table-tab3" role="tab" aria-selected="false" aria-controls="method-summary-table.tabpanel" tabindex="-1" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table-tab3', 3)" class="table-tab">Abstract Methods</button><button id="method-summary-table-tab4" role="tab" aria-selected="false" aria-controls="method-summary-table.tabpanel" tabindex="-1" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table-tab4', 3)" class="table-tab">Concrete Methods</button></div>
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<div class="summary-table three-column-summary">
<div class="table-header col-first">Modifier and Type</div>
<div class="table-header col-second">Method</div>
<div class="table-header col-last">Description</div>
<div class="col-first even-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"><code>protected static void</code></div>
<div class="col-second even-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"><code><a href="#checkAndNudgePoints(com.google.zxing.common.BitMatrix,float%5B%5D)" class="member-name-link">checkAndNudgePoints</a><wbr>(<a href="BitMatrix.html" title="class in com.google.zxing.common">BitMatrix</a> image,
float[] points)</code></div>
<div class="col-last even-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4">
<div class="block">Checks a set of points that have been transformed to sample points on an image against
the image's dimensions to see if the point are even within the image.</div>
</div>
<div class="col-first odd-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"><code>static <a href="GridSampler.html" title="class in com.google.zxing.common">GridSampler</a></code></div>
<div class="col-second odd-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"><code><a href="#getInstance()" class="member-name-link">getInstance</a>()</code></div>
<div class="col-last odd-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"> </div>
<div class="col-first even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code>abstract <a href="BitMatrix.html" title="class in com.google.zxing.common">BitMatrix</a></code></div>
<div class="col-second even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code><a href="#sampleGrid(com.google.zxing.common.BitMatrix,int,int,float,float,float,float,float,float,float,float,float,float,float,float,float,float,float,float)" class="member-name-link">sampleGrid</a><wbr>(<a href="BitMatrix.html" title="class in com.google.zxing.common">BitMatrix</a> image,
int dimensionX,
int dimensionY,
float p1ToX,
float p1ToY,
float p2ToX,
float p2ToY,
float p3ToX,
float p3ToY,
float p4ToX,
float p4ToY,
float p1FromX,
float p1FromY,
float p2FromX,
float p2FromY,
float p3FromX,
float p3FromY,
float p4FromX,
float p4FromY)</code></div>
<div class="col-last even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3">
<div class="block">Samples an image for a rectangular matrix of bits of the given dimension.</div>
</div>
<div class="col-first odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code>abstract <a href="BitMatrix.html" title="class in com.google.zxing.common">BitMatrix</a></code></div>
<div class="col-second odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code><a href="#sampleGrid(com.google.zxing.common.BitMatrix,int,int,com.google.zxing.common.PerspectiveTransform)" class="member-name-link">sampleGrid</a><wbr>(<a href="BitMatrix.html" title="class in com.google.zxing.common">BitMatrix</a> image,
int dimensionX,
int dimensionY,
<a href="PerspectiveTransform.html" title="class in com.google.zxing.common">PerspectiveTransform</a> transform)</code></div>
<div class="col-last odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"> </div>
<div class="col-first even-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"><code>static void</code></div>
<div class="col-second even-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"><code><a href="#setGridSampler(com.google.zxing.common.GridSampler)" class="member-name-link">setGridSampler</a><wbr>(<a href="GridSampler.html" title="class in com.google.zxing.common">GridSampler</a> newGridSampler)</code></div>
<div class="col-last even-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4">
<div class="block">Sets the implementation of GridSampler used by the library.</div>
</div>
</div>
</div>
</div>
<div class="inherited-list">
<h3 id="methods-inherited-from-class-java.lang.Object">Methods inherited from class java.lang.<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html" title="class or interface in java.lang" class="external-link">Object</a></h3>
<code><a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#clone--" title="class or interface in java.lang" class="external-link">clone</a>, <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#equals-java.lang.Object-" title="class or interface in java.lang" class="external-link">equals</a>, <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#finalize--" title="class or interface in java.lang" class="external-link">finalize</a>, <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#getClass--" title="class or interface in java.lang" class="external-link">getClass</a>, <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#hashCode--" title="class or interface in java.lang" class="external-link">hashCode</a>, <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#notify--" title="class or interface in java.lang" class="external-link">notify</a>, <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#notifyAll--" title="class or interface in java.lang" class="external-link">notifyAll</a>, <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#toString--" title="class or interface in java.lang" class="external-link">toString</a>, <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait--" title="class or interface in java.lang" class="external-link">wait</a>, <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-" title="class or interface in java.lang" class="external-link">wait</a>, <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-int-" title="class or interface in java.lang" class="external-link">wait</a></code></div>
</section>
</li>
</ul>
</section>
<section class="details">
<ul class="details-list">
<!-- ========= CONSTRUCTOR DETAIL ======== -->
<li>
<section class="constructor-details" id="constructor-detail">
<h2>Constructor Details</h2>
<ul class="member-list">
<li>
<section class="detail" id="<init>()">
<h3>GridSampler</h3>
<div class="member-signature"><span class="modifiers">public</span> <span class="element-name">GridSampler</span>()</div>
</section>
</li>
</ul>
</section>
</li>
<!-- ============ METHOD DETAIL ========== -->
<li>
<section class="method-details" id="method-detail">
<h2>Method Details</h2>
<ul class="member-list">
<li>
<section class="detail" id="setGridSampler(com.google.zxing.common.GridSampler)">
<h3>setGridSampler</h3>
<div class="member-signature"><span class="modifiers">public static</span> <span class="return-type">void</span> <span class="element-name">setGridSampler</span><wbr><span class="parameters">(<a href="GridSampler.html" title="class in com.google.zxing.common">GridSampler</a> newGridSampler)</span></div>
<div class="block">Sets the implementation of GridSampler used by the library. One global
instance is stored, which may sound problematic. But, the implementation provided
ought to be appropriate for the entire platform, and all uses of this library
in the whole lifetime of the JVM. For instance, an Android activity can swap in
an implementation that takes advantage of native platform libraries.</div>
<dl class="notes">
<dt>Parameters:</dt>
<dd><code>newGridSampler</code> - The platform-specific object to install.</dd>
</dl>
</section>
</li>
<li>
<section class="detail" id="getInstance()">
<h3>getInstance</h3>
<div class="member-signature"><span class="modifiers">public static</span> <span class="return-type"><a href="GridSampler.html" title="class in com.google.zxing.common">GridSampler</a></span> <span class="element-name">getInstance</span>()</div>
<dl class="notes">
<dt>Returns:</dt>
<dd>the current implementation of GridSampler</dd>
</dl>
</section>
</li>
<li>
<section class="detail" id="sampleGrid(com.google.zxing.common.BitMatrix,int,int,float,float,float,float,float,float,float,float,float,float,float,float,float,float,float,float)">
<h3>sampleGrid</h3>
<div class="member-signature"><span class="modifiers">public abstract</span> <span class="return-type"><a href="BitMatrix.html" title="class in com.google.zxing.common">BitMatrix</a></span> <span class="element-name">sampleGrid</span><wbr><span class="parameters">(<a href="BitMatrix.html" title="class in com.google.zxing.common">BitMatrix</a> image,
int dimensionX,
int dimensionY,
float p1ToX,
float p1ToY,
float p2ToX,
float p2ToY,
float p3ToX,
float p3ToY,
float p4ToX,
float p4ToY,
float p1FromX,
float p1FromY,
float p2FromX,
float p2FromY,
float p3FromX,
float p3FromY,
float p4FromX,
float p4FromY)</span>
throws <span class="exceptions"><a href="../NotFoundException.html" title="class in com.google.zxing">NotFoundException</a></span></div>
<div class="block">Samples an image for a rectangular matrix of bits of the given dimension. The sampling
transformation is determined by the coordinates of 4 points, in the original and transformed
image space.</div>
<dl class="notes">
<dt>Parameters:</dt>
<dd><code>image</code> - image to sample</dd>
<dd><code>dimensionX</code> - width of <a href="BitMatrix.html" title="class in com.google.zxing.common"><code>BitMatrix</code></a> to sample from image</dd>
<dd><code>dimensionY</code> - height of <a href="BitMatrix.html" title="class in com.google.zxing.common"><code>BitMatrix</code></a> to sample from image</dd>
<dd><code>p1ToX</code> - point 1 preimage X</dd>
<dd><code>p1ToY</code> - point 1 preimage Y</dd>
<dd><code>p2ToX</code> - point 2 preimage X</dd>
<dd><code>p2ToY</code> - point 2 preimage Y</dd>
<dd><code>p3ToX</code> - point 3 preimage X</dd>
<dd><code>p3ToY</code> - point 3 preimage Y</dd>
<dd><code>p4ToX</code> - point 4 preimage X</dd>
<dd><code>p4ToY</code> - point 4 preimage Y</dd>
<dd><code>p1FromX</code> - point 1 image X</dd>
<dd><code>p1FromY</code> - point 1 image Y</dd>
<dd><code>p2FromX</code> - point 2 image X</dd>
<dd><code>p2FromY</code> - point 2 image Y</dd>
<dd><code>p3FromX</code> - point 3 image X</dd>
<dd><code>p3FromY</code> - point 3 image Y</dd>
<dd><code>p4FromX</code> - point 4 image X</dd>
<dd><code>p4FromY</code> - point 4 image Y</dd>
<dt>Returns:</dt>
<dd><a href="BitMatrix.html" title="class in com.google.zxing.common"><code>BitMatrix</code></a> representing a grid of points sampled from the image within a region
defined by the "from" parameters</dd>
<dt>Throws:</dt>
<dd><code><a href="../NotFoundException.html" title="class in com.google.zxing">NotFoundException</a></code> - if image can't be sampled, for example, if the transformation defined
by the given points is invalid or results in sampling outside the image boundaries</dd>
</dl>
</section>
</li>
<li>
<section class="detail" id="sampleGrid(com.google.zxing.common.BitMatrix,int,int,com.google.zxing.common.PerspectiveTransform)">
<h3>sampleGrid</h3>
<div class="member-signature"><span class="modifiers">public abstract</span> <span class="return-type"><a href="BitMatrix.html" title="class in com.google.zxing.common">BitMatrix</a></span> <span class="element-name">sampleGrid</span><wbr><span class="parameters">(<a href="BitMatrix.html" title="class in com.google.zxing.common">BitMatrix</a> image,
int dimensionX,
int dimensionY,
<a href="PerspectiveTransform.html" title="class in com.google.zxing.common">PerspectiveTransform</a> transform)</span>
throws <span class="exceptions"><a href="../NotFoundException.html" title="class in com.google.zxing">NotFoundException</a></span></div>
<dl class="notes">
<dt>Throws:</dt>
<dd><code><a href="../NotFoundException.html" title="class in com.google.zxing">NotFoundException</a></code></dd>
</dl>
</section>
</li>
<li>
<section class="detail" id="checkAndNudgePoints(com.google.zxing.common.BitMatrix,float[])">
<h3>checkAndNudgePoints</h3>
<div class="member-signature"><span class="modifiers">protected static</span> <span class="return-type">void</span> <span class="element-name">checkAndNudgePoints</span><wbr><span class="parameters">(<a href="BitMatrix.html" title="class in com.google.zxing.common">BitMatrix</a> image,
float[] points)</span>
throws <span class="exceptions"><a href="../NotFoundException.html" title="class in com.google.zxing">NotFoundException</a></span></div>
<div class="block"><p>Checks a set of points that have been transformed to sample points on an image against
the image's dimensions to see if the point are even within the image.</p>
<p>This method will actually "nudge" the endpoints back onto the image if they are found to be
barely (less than 1 pixel) off the image. This accounts for imperfect detection of finder
patterns in an image where the QR Code runs all the way to the image border.</p>
<p>For efficiency, the method will check points from either end of the line until one is found
to be within the image. Because the set of points are assumed to be linear, this is valid.</p></div>
<dl class="notes">
<dt>Parameters:</dt>
<dd><code>image</code> - image into which the points should map</dd>
<dd><code>points</code> - actual points in x1,y1,...,xn,yn form</dd>
<dt>Throws:</dt>
<dd><code><a href="../NotFoundException.html" title="class in com.google.zxing">NotFoundException</a></code> - if an endpoint is lies outside the image boundaries</dd>
</dl>
</section>
</li>
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