--- /dev/null
+/*
+ * Copyright 2007 Google Inc.
+ *
+ * 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.
+ */
+
+package com.google.zxing.common;
+
+import com.google.zxing.MonochromeBitmapSource;
+import com.google.zxing.ReaderException;
+
+/**
+ * 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 srowen@google.com (Sean Owen)
+ */
+public abstract class GridSampler {
+
+ private static GridSampler gridSampler;
+
+ /**
+ * Sets the implementation of {@link 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
+ */
+ public static void setGridSampler(GridSampler newGridSampler) {
+ if (newGridSampler == null) {
+ throw new IllegalArgumentException();
+ }
+ gridSampler = newGridSampler;
+ }
+
+ /**
+ * @return the current implementation of {@link GridSampler}
+ */
+ public static GridSampler getInstance() {
+ if (gridSampler == null) {
+ gridSampler = new DefaultGridSampler();
+ }
+ return gridSampler;
+ }
+
+ /**
+ * <p>Samples an image for a square matrix of bits of the given dimension. This is used to extract the
+ * black/white modules of a 2D barcode like a QR Code found in an image. Because this barcode may be
+ * rotated or perspective-distorted, the caller supplies four points in the source image that define
+ * known points in the barcode, so that the image may be sampled appropriately.</p>
+ *
+ * <p>The last eight "from" parameters are four X/Y coordinate pairs of locations of points in
+ * the image that define some significant points in the image to be sample. For example,
+ * these may be the location of finder pattern in a QR Code.</p>
+ *
+ * <p>The first eight "to" parameters are four X/Y coordinate pairs measured in the destination
+ * {@link BitMatrix}, from the top left, where the known points in the image given by the "from" parameters
+ * map to.</p>
+ *
+ * <p>These 16 parameters define the transformation needed to sample the image.</p>
+ *
+ * @param image image to sample
+ * @param dimension width/height of {@link BitMatrix} to sample from iamge
+ * @return {@link BitMatrix} representing a grid of points sampled from the image within a region
+ * defined by the "from" parameters
+ * @throws ReaderException 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 BitMatrix sampleGrid(MonochromeBitmapSource image,
+ int dimension,
+ 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) throws ReaderException;
+
+ /**
+ * <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 endpoints are even within the image.
+ * This method actually only checks the endpoints since the points are assumed to lie
+ * on a line.</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>
+ *
+ * @param image image into which the points should map
+ * @param points actual points in x1,y1,...,xn,yn form
+ * @throws ReaderException if an endpoint is lies outside the image boundaries
+ */
+ protected static void checkEndpoint(MonochromeBitmapSource image, float[] points) throws ReaderException {
+ int width = image.getWidth();
+ int height = image.getHeight();
+ checkOneEndpoint(points, (int) points[0], (int) points[1], width, height);
+ checkOneEndpoint(points, (int) points[points.length - 2], (int) points[points.length - 1], width, height);
+ }
+
+ private static void checkOneEndpoint(float[] points, int x, int y, int width, int height) throws ReaderException {
+ if (x < -1 || x > width || y < -1 || y > height) {
+ throw new ReaderException("Transformed point out of bounds at " + x + ',' + y);
+ }
+ if (x == -1) {
+ points[0] = 0.0f;
+ }
+ if (y == -1) {
+ points[1] = 0.0f;
+ }
+ if (x == width) {
+ points[0] = width - 1;
+ }
+ if (y == height) {
+ points[1] = height - 1;
+ }
+ }
+
+}
projects / zxing.git / blobdiff