char *TessPDFRenderer::GetPDFTextObjects(TessBaseAPI *api,
double width, double height) {
STRING pdf_str("");
double ppi = api->GetSourceYResolution();
// These initial conditions are all arbitrary and will be overwritten
double old_x = 0.0, old_y = 0.0;
int old_fontsize = 0;
tesseract::WritingDirection old_writing_direction =
WRITING_DIRECTION_LEFT_TO_RIGHT;
bool new_block = true;
int fontsize = 0;
double a = 1;
double b = 0;
double c = 0;
double d = 1;
// TODO(jbreiden) This marries the text and image together.
// Slightly cleaner from an abstraction standpoint if this were to
// live inside a separate text object.
pdf_str += "q ";
pdf_str.add_str_double("", prec(width));
pdf_str += " 0 0 ";
pdf_str.add_str_double("", prec(height));
pdf_str += " 0 0 cm /Im1 Do Q\n";
ResultIterator *res_it = api->GetIterator();
while (!res_it->Empty(RIL_BLOCK)) {
if (res_it->IsAtBeginningOf(RIL_BLOCK)) {
pdf_str += "BT\n3 Tr"; // Begin text object, use invisible ink
old_fontsize = 0; // Every block will declare its fontsize
new_block = true; // Every block will declare its affine matrix
}
int line_x1, line_y1, line_x2, line_y2;
if (res_it->IsAtBeginningOf(RIL_TEXTLINE)) {
int x1, y1, x2, y2;
res_it->Baseline(RIL_TEXTLINE, &x1, &y1, &x2, &y2);
ClipBaseline(ppi, x1, y1, x2, y2, &line_x1, &line_y1, &line_x2, &line_y2);
}
if (res_it->Empty(RIL_WORD)) {
res_it->Next(RIL_WORD);
continue;
}
// Writing direction changes at a per-word granularity
tesseract::WritingDirection writing_direction;
{
tesseract::Orientation orientation;
tesseract::TextlineOrder textline_order;
float deskew_angle;
res_it->Orientation(&orientation, &writing_direction,
&textline_order, &deskew_angle);
if (writing_direction != WRITING_DIRECTION_TOP_TO_BOTTOM) {
switch (res_it->WordDirection()) {
case DIR_LEFT_TO_RIGHT:
writing_direction = WRITING_DIRECTION_LEFT_TO_RIGHT;
break;
case DIR_RIGHT_TO_LEFT:
writing_direction = WRITING_DIRECTION_RIGHT_TO_LEFT;
break;
default:
writing_direction = old_writing_direction;
}
}
}
// Where is word origin and how long is it?
double x, y, word_length;
{
int word_x1, word_y1, word_x2, word_y2;
res_it->Baseline(RIL_WORD, &word_x1, &word_y1, &word_x2, &word_y2);
GetWordBaseline(writing_direction, ppi, height,
word_x1, word_y1, word_x2, word_y2,
line_x1, line_y1, line_x2, line_y2,
&x, &y, &word_length);
}
if (writing_direction != old_writing_direction || new_block) {
AffineMatrix(writing_direction,
line_x1, line_y1, line_x2, line_y2, &a, &b, &c, &d);
pdf_str.add_str_double(" ", prec(a)); // . This affine matrix
pdf_str.add_str_double(" ", prec(b)); // . sets the coordinate
pdf_str.add_str_double(" ", prec(c)); // . system for all
pdf_str.add_str_double(" ", prec(d)); // . text that follows.
pdf_str.add_str_double(" ", prec(x)); // .
pdf_str.add_str_double(" ", prec(y)); // .
pdf_str += (" Tm "); // Place cursor absolutely
new_block = false;
} else {
double dx = x - old_x;
double dy = y - old_y;
pdf_str.add_str_double(" ", prec(dx * a + dy * b));
pdf_str.add_str_double(" ", prec(dx * c + dy * d));
pdf_str += (" Td "); // Relative moveto
}
old_x = x;
old_y = y;
old_writing_direction = writing_direction;
// Adjust font size on a per word granularity. Pay attention to
// fontsize, old_fontsize, and pdf_str. We've found that for
// in Arabic, Tesseract will happily return a fontsize of zero,
// so we make up a default number to protect ourselves.
{
bool bold, italic, underlined, monospace, serif, smallcaps;
int font_id;
res_it->WordFontAttributes(&bold, &italic, &underlined, &monospace,
&serif, &smallcaps, &fontsize, &font_id);
const int kDefaultFontsize = 8;
if (fontsize <= 0)
fontsize = kDefaultFontsize;
if (fontsize != old_fontsize) {
char textfont[20];
snprintf(textfont, sizeof(textfont), "/f-0-0 %d Tf ", fontsize);
pdf_str += textfont;
old_fontsize = fontsize;
}
}
bool last_word_in_line = res_it->IsAtFinalElement(RIL_TEXTLINE, RIL_WORD);
bool last_word_in_block = res_it->IsAtFinalElement(RIL_BLOCK, RIL_WORD);
STRING pdf_word("");
int pdf_word_len = 0;
do {
const char *grapheme = res_it->GetUTF8Text(RIL_SYMBOL);
if (grapheme && grapheme[0] != '\0') {
// TODO(jbreiden) Do a real UTF-16BE conversion
// http://en.wikipedia.org/wiki/UTF-16#Example_UTF-16_encoding_procedure
string_32 utf32;
CubeUtils::UTF8ToUTF32(grapheme, &utf32);
char utf16[20];
for (int i = 0; i < static_cast<int>(utf32.length()); i++) {
snprintf(utf16, sizeof(utf16), "<%04X>", utf32[i]);
pdf_word += utf16;
pdf_word_len++;
}
}
delete[]grapheme;
res_it->Next(RIL_SYMBOL);
} while (!res_it->Empty(RIL_BLOCK) && !res_it->IsAtBeginningOf(RIL_WORD));
if (word_length > 0 && pdf_word_len > 0 && fontsize > 0) {
double h_stretch =
kCharWidth * prec(100.0 * word_length / (fontsize * pdf_word_len));
pdf_str.add_str_double("", h_stretch);
pdf_str += " Tz"; // horizontal stretch
pdf_str += " [ ";
pdf_str += pdf_word; // UTF-16BE representation
pdf_str += " ] TJ"; // show the text
}
if (last_word_in_line) {
pdf_str += " \n";
}
if (last_word_in_block) {
pdf_str += "ET\n"; // end the text object
}
}
char *ret = new char[pdf_str.length() + 1];
strcpy(ret, pdf_str.string());
delete res_it;
return ret;
}
char* TessPDFRenderer::GetPDFTextObjects(TessBaseAPI* api,
double width, double height,
int page_number) {
double ppi = api->GetSourceYResolution();
STRING pdf_str("");
double old_x = 0.0, old_y = 0.0;
int old_pointsize = 0;
// TODO(jbreiden) Slightly cleaner from an abstraction standpoint
// if this were to live inside a separate text object.
pdf_str += "q ";
pdf_str.add_str_double("", prec(width));
pdf_str += " 0 0 ";
pdf_str.add_str_double("", prec(height));
pdf_str += " 0 0 cm /Im1 Do Q\n";
ResultIterator *res_it = api->GetIterator();
while (!res_it->Empty(RIL_BLOCK)) {
if (res_it->IsAtBeginningOf(RIL_BLOCK)) {
pdf_str += "BT\n3 Tr\n"; // Begin text object, use invisible ink
old_pointsize = 0.0; // Every block will declare its font
}
int line_x1, line_y1, line_x2, line_y2;
if (res_it->IsAtBeginningOf(RIL_TEXTLINE)) {
res_it->Baseline(RIL_TEXTLINE,
&line_x1, &line_y1, &line_x2, &line_y2);
double rise = abs(line_y2 - line_y1) * 72 / ppi;
double run = abs(line_x2 - line_x1) * 72 / ppi;
// There are some really stupid PDF viewers in the wild, such as
// 'Preview' which ships with the Mac. They might do a better
// job with text selection and highlighting when given perfectly
// straight text instead of very slightly tilted text. I chose
// this threshold large enough to absorb noise, but small enough
// that lines probably won't cross each other if the whole page
// is tilted at almost exactly the clipping threshold.
if (rise < 2.0 && 2.0 < run)
line_y1 = line_y2 = (line_y1 + line_y2) / 2;
}
if (res_it->Empty(RIL_WORD)) {
res_it->Next(RIL_WORD);
continue;
}
int word_x1, word_y1, word_x2, word_y2;
res_it->Baseline(RIL_WORD, &word_x1, &word_y1, &word_x2, &word_y2);
// The critical one is writing_direction
tesseract::Orientation orientation;
tesseract::WritingDirection writing_direction;
tesseract::TextlineOrder textline_order;
float deskew_angle;
res_it->Orientation(&orientation, &writing_direction,
&textline_order, &deskew_angle);
// Unlike Tesseract, we always want the word baseline in reading order.
if (writing_direction == WRITING_DIRECTION_RIGHT_TO_LEFT) {
Swap(&word_x1, &word_x2);
Swap(&word_y1, &word_y2);
}
// Viewers like evince can get really confused during copy-paste
// when the baseline wanders around. I've decided to force every
// word to match the (straight) baseline. The math below is just
// projecting the word origin onto the baseline. All numbers are
// in the native PDF coordinate system, which has the origin in
// the bottom left and the unit is points, which is 1/72 inch.
double word_length;
double x, y;
{
int px = word_x1;
int py = word_y1;
double l2 = dist2(line_x1, line_y1, line_x2, line_y2);
if (l2 == 0) {
x = line_x1;
y = line_y1;
} else {
double t = ((px - line_x2) * (line_x2 - line_x1) +
(py - line_y2) * (line_y2 - line_y1)) / l2;
x = line_x2 + t * (line_x2 - line_x1);
y = line_y2 + t * (line_y2 - line_y1);
}
word_length = sqrt(static_cast<double>(dist2(word_x1, word_y1,
word_x2, word_y2)));
word_length = word_length * 72.0 / ppi;
x = x * 72 / ppi;
y = height - (y * 72.0 / ppi);
}
int pointsize = 0;
if (res_it->IsAtBeginningOf(RIL_TEXTLINE)) {
// Calculate the rotation angle in the PDF cooordinate system,
// which has the origin in the bottom left. The Tesseract
// coordinate system has the origin in the upper left.
//
// PDF is kind of a like turtle graphics, and we orient the
// turtle (errr... initial cursor position) with an affine
// transformation.
//
// Rotate RTL Translate
//
// [ x' y' 1 ] = [ x y 1 ] [ cos𝜃 -sin𝜃 0 ] [ -1 0 0 ] [ 1 0 0 ]
// [ sin𝜃 cos𝜃 0 ] [ 0 1 0 ] [ 0 1 0 ]
// [ 0 0 1 ] [ 0 0 1 ] [ x y 1 ]
//
double theta = atan2(static_cast<double>(line_y1 - line_y2),
static_cast<double>(line_x2 - line_x1));
double a, b, c, d;
a = cos(theta);
b = sin(theta);
c = -sin(theta);
d = cos(theta);
switch(writing_direction) {
case WRITING_DIRECTION_RIGHT_TO_LEFT:
a = -a;
b = -b;
c = -c;
break;
case WRITING_DIRECTION_TOP_TO_BOTTOM:
// TODO(jbreiden) Consider switching PDF writing mode to vertical.
break;
default:
break;
}
pdf_str.add_str_double("", prec(a)); // . This affine matrix
pdf_str.add_str_double(" ", prec(b)); // . sets the coordinate
pdf_str.add_str_double(" ", prec(c)); // . system for all
pdf_str.add_str_double(" ", prec(d)); // . text in the entire
pdf_str.add_str_double(" ", prec(x)); // . line.
pdf_str.add_str_double(" ", prec(y)); // .
pdf_str += (" Tm "); // Place cursor absolutely
} else {
double offset = sqrt(static_cast<double>(dist2(old_x, old_y, x, y)));
pdf_str.add_str_double(" ", prec(offset)); // Delta x in pts
pdf_str.add_str_double(" ", 0); // Delta y in pts
pdf_str += (" Td "); // Relative moveto
}
old_x = x;
old_y = y;
// Adjust font size on a per word granularity. Pay attention to
// pointsize, old_pointsize, and pdf_str. We've found that for
// in Arabic, Tesseract will happily return a pointsize of zero,
// so we make up a default number to protect ourselves.
{
bool bold, italic, underlined, monospace, serif, smallcaps;
int font_id;
res_it->WordFontAttributes(&bold, &italic, &underlined, &monospace,
&serif, &smallcaps, &pointsize, &font_id);
const int kDefaultPointSize = 8;
if (pointsize <= 0)
pointsize = kDefaultPointSize;
if (pointsize != old_pointsize) {
char textfont[20];
snprintf(textfont, sizeof(textfont), "/f-0-0 %d Tf ", pointsize);
pdf_str += textfont;
old_pointsize = pointsize;
}
}
bool last_word_in_line = res_it->IsAtFinalElement(RIL_TEXTLINE, RIL_WORD);
bool last_word_in_block = res_it->IsAtFinalElement(RIL_BLOCK, RIL_WORD);
STRING pdf_word("");
int pdf_word_len = 0;
do {
const char *grapheme = res_it->GetUTF8Text(RIL_SYMBOL);
if (grapheme && grapheme[0] != '\0') {
// TODO(jbreiden) Do a real UTF-16BE conversion
// http://en.wikipedia.org/wiki/UTF-16#Example_UTF-16_encoding_procedure
string_32 utf32;
CubeUtils::UTF8ToUTF32(grapheme, &utf32);
char utf16[20];
for (int i = 0; i < static_cast<int>(utf32.length()); i++) {
snprintf(utf16, sizeof(utf16), "<%04X>", utf32[i]);
pdf_word += utf16;
pdf_word_len++;
}
}
delete []grapheme;
res_it->Next(RIL_SYMBOL);
} while (!res_it->Empty(RIL_BLOCK) && !res_it->IsAtBeginningOf(RIL_WORD));
if (word_length > 0 && pdf_word_len > 0 && pointsize > 0) {
double h_stretch =
kCharWidth * prec(100.0 * word_length / (pointsize * pdf_word_len));
pdf_str.add_str_double("", h_stretch);
pdf_str += " Tz"; // horizontal stretch
pdf_str += " [ ";
pdf_str += pdf_word; // UTF-16BE representation
pdf_str += " ] TJ"; // show the text
}
if (last_word_in_line) {
pdf_str += " \n";
}
if (last_word_in_block) {
pdf_str += "ET\n"; // end the text object
}
}
char *ret = new char[pdf_str.length() + 1];
strcpy(ret, pdf_str.string());
delete res_it;
return ret;
}
