<?php
/*
* Copyright 2007 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
namespace Zxing\Common;
use Zxing\NotFoundException;
/**
* 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 {@link #setGridSampler(GridSampler)}
* with an instance of a class which implements this interface.
*
* @author Sean Owen
*/
abstract class GridSampler
{
private static $gridSampler;
/**
* Sets the implementation of GridSampler used by the library. One global
* instance is stored, which may sound problematic. But, the implementation provided
* ought to be appropriate for the entire platform, and all uses of this library
* in the whole lifetime of the JVM. For instance, an Android activity can swap in
* an implementation that takes advantage of native platform libraries.
*
* @param newGridSampler The platform-specific object to install.
*/
public static function setGridSampler($newGridSampler)
{
self::$gridSampler = $newGridSampler;
}
/**
* @return the current implementation of GridSampler
*/
public static function getInstance()
{
if (!self::$gridSampler) {
self::$gridSampler = new DefaultGridSampler();
}
return self::$gridSampler;
}
/**
* <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>
*
* @param image image into which the points should map
* @param points actual points in x1,y1,...,xn,yn form
*
* @throws NotFoundException if an endpoint is lies outside the image boundaries
*/
protected static function checkAndNudgePoints(
$image,
$points
) {
$width = $image->getWidth();
$height = $image->getHeight();
// Check and nudge points from start until we see some that are OK:
$nudged = true;
for ($offset = 0; $offset < count($points) && $nudged; $offset += 2) {
$x = (int)$points[$offset];
$y = (int)$points[$offset + 1];
if ($x < -1 || $x > $width || $y < -1 || $y > $height) {
throw NotFoundException::getNotFoundInstance();
}
$nudged = false;
if ($x == -1) {
$points[$offset] = 0.0;
$nudged = true;
} else if ($x == $width) {
$points[$offset] = $width - 1;
$nudged = true;
}
if ($y == -1) {
$points[$offset + 1] = 0.0;
$nudged = true;
} else if ($y == $height) {
$points[$offset + 1] = $height - 1;
$nudged = true;
}
}
// Check and nudge points from end:
$nudged = true;
for ($offset = count($points) - 2; $offset >= 0 && $nudged; $offset -= 2) {
$x = (int)$points[$offset];
$y = (int)$points[$offset + 1];
if ($x < -1 || $x > $width || $y < -1 || $y > $height) {
throw NotFoundException::getNotFoundInstance();
}
$nudged = false;
if ($x == -1) {
$points[$offset] = 0.0;
$nudged = true;
} else if ($x == $width) {
$points[$offset] = $width - 1;
$nudged = true;
}
if ($y == -1) {
$points[$offset + 1] = 0.0;
$nudged = true;
} else if ($y == $height) {
$points[$offset + 1] = $height - 1;
$nudged = true;
}
}
}
/**
* 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.
*
* @param image image to sample
* @param dimensionX width of {@link BitMatrix} to sample from image
* @param dimensionY height of {@link BitMatrix} to sample from image
* @param p1ToX point 1 preimage X
* @param p1ToY point 1 preimage Y
* @param p2ToX point 2 preimage X
* @param p2ToY point 2 preimage Y
* @param p3ToX point 3 preimage X
* @param p3ToY point 3 preimage Y
* @param p4ToX point 4 preimage X
* @param p4ToY point 4 preimage Y
* @param p1FromX point 1 image X
* @param p1FromY point 1 image Y
* @param p2FromX point 2 image X
* @param p2FromY point 2 image Y
* @param p3FromX point 3 image X
* @param p3FromY point 3 image Y
* @param p4FromX point 4 image X
* @param p4FromY point 4 image Y
*
* @return {@link BitMatrix} representing a grid of points sampled from the image within a region
* defined by the "from" parameters
* @throws NotFoundException 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
*/
public abstract function sampleGrid(
$image,
$dimensionX,
$dimensionY,
$p1ToX, $p1ToY,
$p2ToX, $p2ToY,
$p3ToX, $p3ToY,
$p4ToX, $p4ToY,
$p1FromX, $p1FromY,
$p2FromX, $p2FromY,
$p3FromX, $p3FromY,
$p4FromX, $p4FromY
);
public abstract function sampleGrid_(
$image,
$dimensionX,
$dimensionY,
$transform
);
}