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Minor tightening and some new constants (no algo changes)

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git-svn-id: https://zxing.googlecode.com/svn/trunk@1969 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
srowen 2011-10-14 07:47:05 +00:00
parent a75bc5d021
commit 359551d6e7
1 changed files with 47 additions and 39 deletions
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86
core/src/com/google/zxing/common/HybridBinarizer.java
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@ -41,9 +41,12 @@ 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 MINIMUM_DIMENSION = 40; private static final int BLOCK_SIZE_POWER = 3;
private static final int BLOCK_SIZE = 1 << BLOCK_SIZE_POWER;
private static final int BLOCK_SIZE_MASK = BLOCK_SIZE - 1;
private static final int MINIMUM_DIMENSION = BLOCK_SIZE * 5;
private BitMatrix matrix = null; private BitMatrix matrix;
public HybridBinarizer(LuminanceSource source) { public HybridBinarizer(LuminanceSource source) {
super(source); super(source);
@ -61,12 +64,12 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
byte[] luminances = source.getMatrix(); byte[] luminances = source.getMatrix();
int width = source.getWidth(); int width = source.getWidth();
int height = source.getHeight(); int height = source.getHeight();
int subWidth = width >> 3; int subWidth = width >> BLOCK_SIZE_POWER;
if ((width & 0x07) != 0) { if ((width & BLOCK_SIZE_MASK) != 0) {
subWidth++; subWidth++;
} }
int subHeight = height >> 3; int subHeight = height >> BLOCK_SIZE_POWER;
if ((height & 0x07) != 0) { if ((height & BLOCK_SIZE_MASK) != 0) {
subHeight++; subHeight++;
} }
int[][] blackPoints = calculateBlackPoints(luminances, subWidth, subHeight, width, height); int[][] blackPoints = calculateBlackPoints(luminances, subWidth, subHeight, width, height);
@ -88,17 +91,22 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
// For each 8x8 block in the image, calculate the average black point using a 5x5 grid // 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 // of the blocks around it. Also handles the corner cases (fractional blocks are computed based
// on the last 8 pixels in the row/column which are also used in the previous block). // on the last 8 pixels in the row/column which are also used in the previous block).
private static void calculateThresholdForBlock(byte[] luminances, int subWidth, int subHeight, private static void calculateThresholdForBlock(byte[] luminances,
int width, int height, int[][] blackPoints, BitMatrix matrix) { 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 << 3; int yoffset = y << BLOCK_SIZE_POWER;
if ((yoffset + 8) >= height) { if ((yoffset + BLOCK_SIZE) >= height) {
yoffset = height - 8; yoffset = height - BLOCK_SIZE;
} }
for (int x = 0; x < subWidth; x++) { for (int x = 0; x < subWidth; x++) {
int xoffset = x << 3; int xoffset = x << BLOCK_SIZE_POWER;
if ((xoffset + 8) >= width) { if ((xoffset + BLOCK_SIZE) >= width) {
xoffset = width - 8; xoffset = width - BLOCK_SIZE;
} }
int left = x > 1 ? x : 2; int left = x > 1 ? x : 2;
left = left < subWidth - 2 ? left : subWidth - 3; left = left < subWidth - 2 ? left : subWidth - 3;
@ -107,11 +115,7 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
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]; sum += blackRow[left - 2] + blackRow[left - 1] + blackRow[left] + blackRow[left + 1] + blackRow[left + 2];
sum += blackRow[left - 1];
sum += blackRow[left];
sum += blackRow[left + 1];
sum += blackRow[left + 2];
} }
int average = sum / 25; int average = sum / 25;
threshold8x8Block(luminances, xoffset, yoffset, average, width, matrix); threshold8x8Block(luminances, xoffset, yoffset, average, width, matrix);
@ -120,13 +124,15 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
} }
// Applies a single threshold to an 8x8 block of pixels. // Applies a single threshold to an 8x8 block of pixels.
private static void threshold8x8Block(byte[] luminances, int xoffset, int yoffset, int threshold, private static void threshold8x8Block(byte[] luminances,
int stride, BitMatrix matrix) { int xoffset,
for (int y = 0; y < 8; y++) { int yoffset,
int offset = (yoffset + y) * stride + xoffset; int threshold,
for (int x = 0; x < 8; x++) { int stride,
int pixel = luminances[offset + x] & 0xff; BitMatrix matrix) {
if (pixel < threshold) { for (int y = 0, offset = yoffset * stride + xoffset; y < BLOCK_SIZE; y++, offset += stride) {
for (int x = 0; x < BLOCK_SIZE; x++) {
if ((luminances[offset + x] & 0xFF) < threshold) {
matrix.set(xoffset + x, yoffset + y); matrix.set(xoffset + x, yoffset + y);
} }
} }
@ -134,26 +140,28 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
} }
// Calculates a single black point for each 8x8 block of pixels and saves it away. // Calculates a single black point for each 8x8 block of pixels and saves it away.
private static int[][] calculateBlackPoints(byte[] luminances, int subWidth, int subHeight, private static int[][] calculateBlackPoints(byte[] luminances,
int width, int height) { 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 << 3; int yoffset = y << BLOCK_SIZE_POWER;
if ((yoffset + 8) >= height) { if ((yoffset + BLOCK_SIZE) >= height) {
yoffset = height - 8; yoffset = height - BLOCK_SIZE;
} }
for (int x = 0; x < subWidth; x++) { for (int x = 0; x < subWidth; x++) {
int xoffset = x << 3; int xoffset = x << BLOCK_SIZE_POWER;
if ((xoffset + 8) >= width) { if ((xoffset + BLOCK_SIZE) >= width) {
xoffset = width - 8; xoffset = width - BLOCK_SIZE;
} }
int sum = 0; int sum = 0;
int min = 255; int min = 0xFF;
int max = 0; int max = 0;
for (int yy = 0; yy < 8; yy++) { for (int yy = 0, offset = yoffset * width + xoffset; yy < BLOCK_SIZE; yy++, offset += width) {
int offset = (yoffset + yy) * width + xoffset; for (int xx = 0; xx < BLOCK_SIZE; xx++) {
for (int xx = 0; xx < 8; xx++) { int pixel = luminances[offset + xx] & 0xFF;
int pixel = luminances[offset + xx] & 0xff;
sum += pixel; sum += pixel;
if (pixel < min) { if (pixel < min) {
min = pixel; min = pixel;