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Cleaned up a number of comments and code to fit in 100 columns and added some TODO items.

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git-svn-id: https://zxing.googlecode.com/svn/trunk@1013 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
dswitkin 2009-07-01 16:35:05 +00:00
parent e44f00ba75
commit af2ce46c37
1 changed files with 54 additions and 69 deletions
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123
core/src/com/google/zxing/pdf417/detector/Detector.java
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@ -26,10 +26,8 @@ import com.google.zxing.common.GridSampler;
import java.util.Hashtable; import java.util.Hashtable;
/** /**
* <p> * <p>Encapsulates logic that can detect a PDF417 Code in an image, even if the
* Encapsulates logic that can detect a PDF417 Code in an image, even if the * PDF417 Code is rotated or skewed, or partially obscured.</p>
* PDF417 Code is rotated or skewed, or partially obscured.
* </p>
* *
* @author SITA Lab (kevin.osullivan@sita.aero) * @author SITA Lab (kevin.osullivan@sita.aero)
*/ */
@ -59,12 +57,9 @@ public final class Detector {
} }
/** /**
* <p> * <p>Detects a PDF417 Code in an image, simply.</p>
* Detects a PDF417 Code in an image, simply.
* </p>
* *
* @return {@link DetectorResult} encapsulating results of detecting a PDF417 * @return {@link DetectorResult} encapsulating results of detecting a PDF417 Code
* Code
* @throws ReaderException if no QR Code can be found * @throws ReaderException if no QR Code can be found
*/ */
public DetectorResult detect() throws ReaderException { public DetectorResult detect() throws ReaderException {
@ -72,32 +67,23 @@ public final class Detector {
} }
/** /**
* <p> * <p>Detects a PDF417 Code in an image. Only checks 0 and 180 degree rotations.</p>
* Detects a PDF417 Code in an image, simply.
* </p>
* *
* @param hints optional hints to detector * @param hints optional hints to detector
* @return {@link DetectorResult} encapsulating results of detecting a PDF417 * @return {@link DetectorResult} encapsulating results of detecting a PDF417 Code
* Code
* @throws ReaderException if no PDF417 Code can be found * @throws ReaderException if no PDF417 Code can be found
*/ */
public DetectorResult detect(Hashtable hints) throws ReaderException { public DetectorResult detect(Hashtable hints) throws ReaderException {
// Fetch the 1 bit matrix once up front. // Fetch the 1 bit matrix once up front.
BitMatrix matrix = image.getBlackMatrix(); BitMatrix matrix = image.getBlackMatrix();
// Try to find the vertices assuming the image is upright.
ResultPoint[] vertices = findVertices(matrix); ResultPoint[] vertices = findVertices(matrix);
if (vertices == null) { // Couldn't find the vertices if (vertices == null) {
// Maybe the image is rotated 180 degrees? // Maybe the image is rotated 180 degrees?
vertices = findVertices180(matrix); vertices = findVertices180(matrix);
/*
* // Don't need this because the PDF417 code won't fit into // the
* camera view finder when it is rotated. if (vertices == null) { //
* Couldn't find the vertices // Maybe the image is rotated 90 degrees?
* vertices = findVertices90(image); if (vertices == null) { //
* Couldn't find the vertices // Maybe the image is rotated 270
* degrees? vertices = findVertices270(image); } }
*/
} }
if (vertices != null) { if (vertices != null) {
float moduleWidth = computeModuleWidth(vertices); float moduleWidth = computeModuleWidth(vertices);
if (moduleWidth < 1.0f) { if (moduleWidth < 1.0f) {
@ -107,10 +93,9 @@ public final class Detector {
int dimension = computeDimension(vertices[4], vertices[6], int dimension = computeDimension(vertices[4], vertices[6],
vertices[5], vertices[7], moduleWidth); vertices[5], vertices[7], moduleWidth);
// Deskew and sample image // Deskew and sample image.
BitMatrix bits = sampleGrid(matrix, vertices[4], vertices[5], BitMatrix bits = sampleGrid(matrix, vertices[4], vertices[5],
vertices[6], vertices[7], dimension); vertices[6], vertices[7], dimension);
//bits.setModuleWidth(moduleWidth);
return new DetectorResult(bits, new ResultPoint[]{vertices[4], return new DetectorResult(bits, new ResultPoint[]{vertices[4],
vertices[5], vertices[6], vertices[7]}); vertices[5], vertices[6], vertices[7]});
} else { } else {
@ -126,12 +111,15 @@ public final class Detector {
* TODO: Scanning every row is very expensive. We should only do this for TRY_HARDER. * TODO: Scanning every row is very expensive. We should only do this for TRY_HARDER.
* *
* @param matrix the scanned barcode image. * @param matrix the scanned barcode image.
* @return the an array containing the vertices. vertices[0] x, y top left * @return an array containing the vertices:
* barcode vertices[1] x, y bottom left barcode vertices[2] x, y top * vertices[0] x, y top left barcode
* right barcode vertices[3] x, y bottom right barcode vertices[4] x, * vertices[1] x, y bottom left barcode
* y top left codeword area vertices[5] x, y bottom left codeword * vertices[2] x, y top right barcode
* area vertices[6] x, y top right codeword area vertices[7] x, y * vertices[3] x, y bottom right barcode
* bottom right codeword area * vertices[4] x, y top left codeword area
* vertices[5] x, y bottom left codeword area
* vertices[6] x, y top right codeword area
* vertices[7] x, y bottom right codeword area
*/ */
private static ResultPoint[] findVertices(BitMatrix matrix) throws ReaderException { private static ResultPoint[] findVertices(BitMatrix matrix) throws ReaderException {
int height = matrix.getHeight(); int height = matrix.getHeight();
@ -203,12 +191,15 @@ public final class Detector {
* TODO: Scanning every row is very expensive. We should only do this for TRY_HARDER. * TODO: Scanning every row is very expensive. We should only do this for TRY_HARDER.
* *
* @param matrix the scanned barcode image. * @param matrix the scanned barcode image.
* @return the an array containing the vertices. vertices[0] x, y top left * @return an array containing the vertices:
* barcode vertices[1] x, y bottom left barcode vertices[2] x, y top * vertices[0] x, y top left barcode
* right barcode vertices[3] x, y bottom right barcode vertices[4] x, * vertices[1] x, y bottom left barcode
* y top left codeword area vertices[5] x, y bottom left codeword * vertices[2] x, y top right barcode
* area vertices[6] x, y top right codeword area vertices[7] x, y * vertices[3] x, y bottom right barcode
* bottom right codeword area * vertices[4] x, y top left codeword area
* vertices[5] x, y bottom left codeword area
* vertices[6] x, y top right codeword area
* vertices[7] x, y bottom right codeword area
*/ */
private static ResultPoint[] findVertices180(BitMatrix matrix) throws ReaderException { private static ResultPoint[] findVertices180(BitMatrix matrix) throws ReaderException {
int height = matrix.getHeight(); int height = matrix.getHeight();
@ -272,15 +263,18 @@ public final class Detector {
} }
/** /**
* <p> * <p>Estimates module size (pixels in a module) based on the Start and End
* Estimates module size (pixels in a module) based on the Start and End
* finder patterns.</p> * finder patterns.</p>
* *
* @param vertices [] vertices[0] x, y top left barcode vertices[1] x, y bottom * @param vertices an array of vertices:
* left barcode vertices[2] x, y top right barcode vertices[3] x, y * vertices[0] x, y top left barcode
* bottom right barcode vertices[4] x, y top left Codeword area * vertices[1] x, y bottom left barcode
* vertices[5] x, y bottom left Codeword area vertices[6] x, y top * vertices[2] x, y top right barcode
* right Codeword area vertices[7] x, y bottom right Codeword area * vertices[3] x, y bottom right barcode
* vertices[4] x, y top left codeword area
* vertices[5] x, y bottom left codeword area
* vertices[6] x, y top right codeword area
* vertices[7] x, y bottom right codeword area
* @return the module size. * @return the module size.
*/ */
private static float computeModuleWidth(ResultPoint[] vertices) { private static float computeModuleWidth(ResultPoint[] vertices) {
@ -306,12 +300,8 @@ public final class Detector {
*/ */
private static int computeDimension(ResultPoint topLeft, ResultPoint topRight, private static int computeDimension(ResultPoint topLeft, ResultPoint topRight,
ResultPoint bottomLeft, ResultPoint bottomRight, float moduleWidth) { ResultPoint bottomLeft, ResultPoint bottomRight, float moduleWidth) {
int topRowDimension = round(ResultPoint int topRowDimension = round(ResultPoint.distance(topLeft, topRight) / moduleWidth);
.distance(topLeft, topRight) int bottomRowDimension = round(ResultPoint.distance(bottomLeft, bottomRight) / moduleWidth);
/ moduleWidth);
int bottomRowDimension = round(ResultPoint.distance(bottomLeft,
bottomRight)
/ moduleWidth);
return ((((topRowDimension + bottomRowDimension) >> 1) + 8) / 17) * 17; return ((((topRowDimension + bottomRowDimension) >> 1) + 8) / 17) * 17;
/* /*
* int topRowDimension = round(ResultPoint.distance(topLeft, * int topRowDimension = round(ResultPoint.distance(topLeft,
@ -328,8 +318,7 @@ public final class Detector {
ResultPoint bottomLeft, ResultPoint topRight, ResultPoint bottomRight, int dimension) ResultPoint bottomLeft, ResultPoint topRight, ResultPoint bottomRight, int dimension)
throws ReaderException { throws ReaderException {
// Note that unlike in the QR Code sampler, we didn't find the center of // Note that unlike the QR Code sampler, we didn't find the center of modules, but the
// modules, but the
// very corners. So there is no 0.5f here; 0.0f is right. // very corners. So there is no 0.5f here; 0.0f is right.
GridSampler sampler = GridSampler.getInstance(); GridSampler sampler = GridSampler.getInstance();
@ -349,7 +338,6 @@ public final class Detector {
bottomRight.getY(), // p3FromY bottomRight.getY(), // p3FromY
bottomLeft.getX(), // p4FromX bottomLeft.getX(), // p4FromX
bottomLeft.getY()); // p4FromY bottomLeft.getY()); // p4FromY
} }
/** /**
@ -365,12 +353,14 @@ public final class Detector {
* @param column x position to start search * @param column x position to start search
* @param row y position to start search * @param row y position to start search
* @param width the number of pixels to search on this row * @param width the number of pixels to search on this row
* @param pattern pattern of counts of number of black and white pixels that are * @param pattern pattern of counts of number of black and white pixels that are
* being searched for as a pattern * being searched for as a pattern
* @return start/end horizontal offset of guard pattern, as an array of two ints. * @return start/end horizontal offset of guard pattern, as an array of two ints.
*/ */
static int[] findGuardPattern(BitMatrix matrix, int column, int row, int width, int[] pattern) { static int[] findGuardPattern(BitMatrix matrix, int column, int row, int width, int[] pattern) {
int patternLength = pattern.length; int patternLength = pattern.length;
// TODO: Find a way to cache this array, as this method is called hundreds of times
// per image, and we want to allocate as seldom as possible.
int[] counters = new int[patternLength]; int[] counters = new int[patternLength];
boolean isWhite = false; boolean isWhite = false;
@ -408,8 +398,8 @@ public final class Detector {
* the total variance from the expected pattern proportions across all * the total variance from the expected pattern proportions across all
* pattern elements, to the length of the pattern. * pattern elements, to the length of the pattern.
* *
* @param counters observed counters * @param counters observed counters
* @param pattern expected pattern * @param pattern expected pattern
* @param maxIndividualVariance The most any counter can differ before we give up * @param maxIndividualVariance The most any counter can differ before we give up
* @return ratio of total variance between counters and pattern compared to * @return ratio of total variance between counters and pattern compared to
* total pattern size, where the ratio has been multiplied by 256. * total pattern size, where the ratio has been multiplied by 256.
@ -417,8 +407,7 @@ public final class Detector {
* variance between counters and patterns equals the pattern length, * variance between counters and patterns equals the pattern length,
* higher values mean even more variance * higher values mean even more variance
*/ */
public static int patternMatchVariance(int[] counters, int[] pattern, public static int patternMatchVariance(int[] counters, int[] pattern, int maxIndividualVariance) {
int maxIndividualVariance) {
int numCounters = counters.length; int numCounters = counters.length;
int total = 0; int total = 0;
int patternLength = 0; int patternLength = 0;
@ -428,15 +417,12 @@ public final class Detector {
} }
if (total < patternLength) { if (total < patternLength) {
// If we don't even have one pixel per unit of bar width, assume this // If we don't even have one pixel per unit of bar width, assume this
// is too small // is too small to reliably match, so fail:
// to reliably match, so fail:
return Integer.MAX_VALUE; return Integer.MAX_VALUE;
} }
// We're going to fake floating-point math in integers. We just need to // We're going to fake floating-point math in integers. We just need to use more bits.
// use more bits. // Scale up patternLength so that intermediate values below like scaledCounter will have
// Scale up patternLength so that intermediate values below like // more "significant digits".
// scaledCounter will have
// more "significant digits"
int unitBarWidth = (total << 8) / patternLength; int unitBarWidth = (total << 8) / patternLength;
maxIndividualVariance = (maxIndividualVariance * unitBarWidth) >> 8; maxIndividualVariance = (maxIndividualVariance * unitBarWidth) >> 8;
@ -444,8 +430,7 @@ public final class Detector {
for (int x = 0; x < numCounters; x++) { for (int x = 0; x < numCounters; x++) {
int counter = counters[x] << 8; int counter = counters[x] << 8;
int scaledPattern = pattern[x] * unitBarWidth; int scaledPattern = pattern[x] * unitBarWidth;
int variance = counter > scaledPattern ? counter - scaledPattern int variance = counter > scaledPattern ? counter - scaledPattern : scaledPattern - counter;
: scaledPattern - counter;
if (variance > maxIndividualVariance) { if (variance > maxIndividualVariance) {
return Integer.MAX_VALUE; return Integer.MAX_VALUE;
} }