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Hunting an AIOOBE here -- clarified some code a little bit but still not seeing the issue

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git-svn-id: https://zxing.googlecode.com/svn/trunk@2277 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
srowen 2012-04-30 07:22:26 +00:00
parent 224568c732
commit 60288ac9e4
1 changed files with 62 additions and 38 deletions
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98
core/src/com/google/zxing/common/HybridBinarizer.java
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@ -42,8 +42,8 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
// This class uses 5x5 blocks to compute local luminance, where each block is 8x8 pixels. // This class uses 5x5 blocks to compute local luminance, where each block is 8x8 pixels.
// So this is the smallest dimension in each axis we can accept. // So this is the smallest dimension in each axis we can accept.
private static final int BLOCK_SIZE_POWER = 3; private static final int BLOCK_SIZE_POWER = 3;
private static final int BLOCK_SIZE = 1 << BLOCK_SIZE_POWER; private static final int BLOCK_SIZE = 1 << BLOCK_SIZE_POWER; // ...0100...00
private static final int BLOCK_SIZE_MASK = BLOCK_SIZE - 1; private static final int BLOCK_SIZE_MASK = BLOCK_SIZE - 1; // ...0011...11
private static final int MINIMUM_DIMENSION = BLOCK_SIZE * 5; private static final int MINIMUM_DIMENSION = BLOCK_SIZE * 5;
private static final int MIN_DYNAMIC_RANGE = 24; private static final int MIN_DYNAMIC_RANGE = 24;
@ -53,19 +53,21 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
super(source); super(source);
} }
/**
* Calculates the final BitMatrix once for all requests. This could be called once from the
* constructor instead, but there are some advantages to doing it lazily, such as making
* profiling easier, and not doing heavy lifting when callers don't expect it.
*/
@Override @Override
public BitMatrix getBlackMatrix() throws NotFoundException { public BitMatrix getBlackMatrix() throws NotFoundException {
// Calculates the final BitMatrix once for all requests. This could be called once from the
// constructor instead, but there are some advantages to doing it lazily, such as making
// profiling easier, and not doing heavy lifting when callers don't expect it.
if (matrix != null) { if (matrix != null) {
return matrix; return matrix;
} }
LuminanceSource source = getLuminanceSource(); LuminanceSource source = getLuminanceSource();
if (source.getWidth() >= MINIMUM_DIMENSION && source.getHeight() >= MINIMUM_DIMENSION) {
byte[] luminances = source.getMatrix();
int width = source.getWidth(); int width = source.getWidth();
int height = source.getHeight(); int height = source.getHeight();
if (width >= MINIMUM_DIMENSION && height >= MINIMUM_DIMENSION) {
byte[] luminances = source.getMatrix();
int subWidth = width >> BLOCK_SIZE_POWER; int subWidth = width >> BLOCK_SIZE_POWER;
if ((width & BLOCK_SIZE_MASK) != 0) { if ((width & BLOCK_SIZE_MASK) != 0) {
subWidth++; subWidth++;
@ -77,8 +79,7 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
int[][] blackPoints = calculateBlackPoints(luminances, subWidth, subHeight, width, height); int[][] blackPoints = calculateBlackPoints(luminances, subWidth, subHeight, width, height);
BitMatrix newMatrix = new BitMatrix(width, height); BitMatrix newMatrix = new BitMatrix(width, height);
calculateThresholdForBlock(luminances, subWidth, subHeight, width, height, blackPoints, calculateThresholdForBlock(luminances, subWidth, subHeight, width, height, blackPoints, newMatrix);
newMatrix);
matrix = newMatrix; matrix = newMatrix;
} else { } else {
// If the image is too small, fall back to the global histogram approach. // If the image is too small, fall back to the global histogram approach.
@ -92,40 +93,56 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
return new HybridBinarizer(source); return new HybridBinarizer(source);
} }
// For each 8x8 block in the image, calculate the average black point using a 5x5 grid /**
// of the blocks around it. Also handles the corner cases (fractional blocks are computed based * For each block in the image, calculate the average black point using a 5x5 grid
// on the last 8 pixels in the row/column which are also used in the previous block). * of the blocks around it. Also handles the corner cases (fractional blocks are computed based
private static void calculateThresholdForBlock(byte[] luminances, int subWidth, int subHeight, * on the last pixels in the row/column which are also used in the previous block).
int width, int height, int[][] blackPoints, BitMatrix matrix) { */
private static void calculateThresholdForBlock(byte[] luminances,
int subWidth,
int subHeight,
int width,
int height,
int[][] blackPoints,
BitMatrix matrix) {
for (int y = 0; y < subHeight; y++) { for (int y = 0; y < subHeight; y++) {
int yoffset = y << BLOCK_SIZE_POWER; int yoffset = y << BLOCK_SIZE_POWER;
if ((yoffset + BLOCK_SIZE) >= height) { int maxYOffset = height - BLOCK_SIZE;
yoffset = height - BLOCK_SIZE; if (yoffset > maxYOffset) {
yoffset = maxYOffset;
} }
for (int x = 0; x < subWidth; x++) { for (int x = 0; x < subWidth; x++) {
int xoffset = x << BLOCK_SIZE_POWER; int xoffset = x << BLOCK_SIZE_POWER;
if ((xoffset + BLOCK_SIZE) >= width) { int maxXOffset = width - BLOCK_SIZE;
xoffset = width - BLOCK_SIZE; if (xoffset > maxXOffset) {
xoffset = maxXOffset;
} }
int left = x > 1 ? x : 2; int left = cap(x, 2, subWidth - 3);
left = left < subWidth - 2 ? left : subWidth - 3; int top = cap(y, 2, subHeight - 3);
int top = y > 1 ? y : 2;
top = top < subHeight - 2 ? top : subHeight - 3;
int sum = 0; int sum = 0;
for (int z = -2; z <= 2; z++) { for (int z = -2; z <= 2; z++) {
int[] blackRow = blackPoints[top + z]; int[] blackRow = blackPoints[top + z];
sum += blackRow[left - 2] + blackRow[left - 1] + blackRow[left] + blackRow[left + 1] + sum += blackRow[left - 2] + blackRow[left - 1] + blackRow[left] + blackRow[left + 1] + blackRow[left + 2];
blackRow[left + 2];
} }
int average = sum / 25; int average = sum / 25;
threshold8x8Block(luminances, xoffset, yoffset, average, width, matrix); thresholdBlock(luminances, xoffset, yoffset, average, width, matrix);
} }
} }
} }
// Applies a single threshold to an 8x8 block of pixels. private static int cap(int value, int min, int max) {
private static void threshold8x8Block(byte[] luminances, int xoffset, int yoffset, int threshold, return value < min ? min : value > max ? max : value;
int stride, BitMatrix matrix) { }
/**
* Applies a single threshold to a block of pixels.
*/
private static void thresholdBlock(byte[] luminances,
int xoffset,
int yoffset,
int threshold,
int stride,
BitMatrix matrix) {
for (int y = 0, offset = yoffset * stride + xoffset; y < BLOCK_SIZE; y++, offset += stride) { for (int y = 0, offset = yoffset * stride + xoffset; y < BLOCK_SIZE; y++, offset += stride) {
for (int x = 0; x < BLOCK_SIZE; x++) { for (int x = 0; x < BLOCK_SIZE; x++) {
// Comparison needs to be <= so that black == 0 pixels are black even if the threshold is 0. // Comparison needs to be <= so that black == 0 pixels are black even if the threshold is 0.
@ -136,21 +153,28 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
} }
} }
// Calculates a single black point for each 8x8 block of pixels and saves it away. /**
// See the following thread for a discussion of this algorithm: * Calculates a single black point for each block of pixels and saves it away.
// http://groups.google.com/group/zxing/browse_thread/thread/d06efa2c35a7ddc0 * See the following thread for a discussion of this algorithm:
private static int[][] calculateBlackPoints(byte[] luminances, int subWidth, int subHeight, * http://groups.google.com/group/zxing/browse_thread/thread/d06efa2c35a7ddc0
int width, int height) { */
private static int[][] calculateBlackPoints(byte[] luminances,
int subWidth,
int subHeight,
int width,
int height) {
int[][] blackPoints = new int[subHeight][subWidth]; int[][] blackPoints = new int[subHeight][subWidth];
for (int y = 0; y < subHeight; y++) { for (int y = 0; y < subHeight; y++) {
int yoffset = y << BLOCK_SIZE_POWER; int yoffset = y << BLOCK_SIZE_POWER;
if ((yoffset + BLOCK_SIZE) >= height) { int maxYOffset = height - BLOCK_SIZE;
yoffset = height - BLOCK_SIZE; if (yoffset > maxYOffset) {
yoffset = maxYOffset;
} }
for (int x = 0; x < subWidth; x++) { for (int x = 0; x < subWidth; x++) {
int xoffset = x << BLOCK_SIZE_POWER; int xoffset = x << BLOCK_SIZE_POWER;
if ((xoffset + BLOCK_SIZE) >= width) { int maxXOffset = width - BLOCK_SIZE;
xoffset = width - BLOCK_SIZE; if (xoffset > maxXOffset) {
xoffset = maxXOffset;
} }
int sum = 0; int sum = 0;
int min = 0xFF; int min = 0xFF;