int width = source.getWidth();
int height = source.getHeight();
int subWidth = width >> 3;
+ if ((width & 0x07) != 0) {
+ subWidth++;
+ }
int subHeight = height >> 3;
- int[][] blackPoints = calculateBlackPoints(luminances, subWidth, subHeight, width);
+ if ((height & 0x07) != 0) {
+ subHeight++;
+ }
+ int[][] blackPoints = calculateBlackPoints(luminances, subWidth, subHeight, width, height);
matrix = new BitMatrix(width, height);
- calculateThresholdForBlock(luminances, subWidth, subHeight, width, blackPoints, matrix);
+ calculateThresholdForBlock(luminances, subWidth, subHeight, width, height, blackPoints, matrix);
} else {
// If the image is too small, fall back to the global histogram approach.
matrix = super.getBlackMatrix();
}
// 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, but will ignore up to 7 pixels
- // on the right edge and 7 pixels at the bottom of the image if the overall dimensions are not
- // multiples of eight. In practice, leaving those pixels white does not seem to be a problem.
+ // 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).
private static void calculateThresholdForBlock(byte[] luminances, int subWidth, int subHeight,
- int stride, int[][] blackPoints, BitMatrix matrix) {
+ int width, int height, int[][] blackPoints, BitMatrix matrix) {
for (int y = 0; y < subHeight; y++) {
+ int yoffset = y << 3;
+ if ((yoffset + 8) >= height) {
+ yoffset = height - 8;
+ }
for (int x = 0; x < subWidth; x++) {
+ int xoffset = x << 3;
+ if ((xoffset + 8) >= width) {
+ xoffset = width - 8;
+ }
int left = (x > 1) ? x : 2;
left = (left < subWidth - 2) ? left : subWidth - 3;
int top = (y > 1) ? y : 2;
sum += blackRow[left + 2];
}
int average = sum / 25;
- threshold8x8Block(luminances, x << 3, y << 3, average, stride, matrix);
+ threshold8x8Block(luminances, xoffset, yoffset, average, width, matrix);
}
}
}
// 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,
- int stride) {
+ int width, int height) {
int[][] blackPoints = new int[subHeight][subWidth];
for (int y = 0; y < subHeight; y++) {
+ int yoffset = y << 3;
+ if ((yoffset + 8) >= height) {
+ yoffset = height - 8;
+ }
for (int x = 0; x < subWidth; x++) {
+ int xoffset = x << 3;
+ if ((xoffset + 8) >= width) {
+ xoffset = width - 8;
+ }
int sum = 0;
int min = 255;
int max = 0;
for (int yy = 0; yy < 8; yy++) {
- int offset = ((y << 3) + yy) * stride + (x << 3);
+ int offset = (yoffset + yy) * width + xoffset;
for (int xx = 0; xx < 8; xx++) {
int pixel = luminances[offset + xx] & 0xff;
sum += pixel;
int width = source->getWidth();
int height = source->getHeight();
int subWidth = width >> 3;
+ if (width & 0x07) {
+ subWidth++;
+ }
int subHeight = height >> 3;
- int *blackPoints = calculateBlackPoints(luminances, subWidth, subHeight, width);
+ if (height & 0x07) {
+ subHeight++;
+ }
+ int *blackPoints = calculateBlackPoints(luminances, subWidth, subHeight, width, height);
cached_matrix_.reset(new BitMatrix(width,height));
- calculateThresholdForBlock(luminances, subWidth, subHeight, width, blackPoints, cached_matrix_);
+ calculateThresholdForBlock(luminances, subWidth, subHeight, width, height, blackPoints, cached_matrix_);
delete [] blackPoints;
delete [] luminances;
} else {
}
void HybridBinarizer::calculateThresholdForBlock(unsigned char* luminances, int subWidth, int subHeight,
- int stride, int blackPoints[], Ref<BitMatrix> matrix) {
+ int width, int height, int blackPoints[], Ref<BitMatrix> matrix) {
for (int y = 0; y < subHeight; y++) {
+ int yoffset = y << 3;
+ if (yoffset + 8 >= height) {
+ yoffset = height - 8;
+ }
for (int x = 0; x < subWidth; x++) {
+ int xoffset = x << 3;
+ if (xoffset + 8 >= width) {
+ xoffset = width - 8;
+ }
int left = (x > 1) ? x : 2;
left = (left < subWidth - 2) ? left : subWidth - 3;
int top = (y > 1) ? y : 2;
sum += blackRow[left + 2];
}
int average = sum / 25;
- threshold8x8Block(luminances, x << 3, y << 3, average, stride, matrix);
+ threshold8x8Block(luminances, xoffset, yoffset, average, width, matrix);
}
}
}
}
int* HybridBinarizer::calculateBlackPoints(unsigned char* luminances, int subWidth, int subHeight,
- int stride) {
+ int width, int height) {
int *blackPoints = new int[subHeight * subWidth];
for (int y = 0; y < subHeight; y++) {
+ int yoffset = y << 3;
+ if (yoffset + 8 >= height) {
+ yoffset = height - 8;
+ }
for (int x = 0; x < subWidth; x++) {
+ int xoffset = x << 3;
+ if (xoffset + 8 >= width) {
+ xoffset = width - 8;
+ }
int sum = 0;
int min = 255;
int max = 0;
for (int yy = 0; yy < 8; yy++) {
- int offset = ((y << 3) + yy) * stride + (x << 3);
+ int offset = (yoffset + yy) * width + xoffset;
for (int xx = 0; xx < 8; xx++) {
int pixel = luminances[offset + xx] & 0xff;
sum += pixel;
void binarizeEntireImage();
// We'll be using one-D arrays because C++ can't dynamically allocate 2D arrays
int* calculateBlackPoints(unsigned char* luminances, int subWidth, int subHeight,
- int stride);
+ int width, int height);
void calculateThresholdForBlock(unsigned char* luminances, int subWidth, int subHeight,
- int stride, int blackPoints[], Ref<BitMatrix> matrix);
+ int width, int height, int blackPoints[], Ref<BitMatrix> matrix);
void threshold8x8Block(unsigned char* luminances, int xoffset, int yoffset, int threshold,
int stride, Ref<BitMatrix> matrix);
};