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tesseract/training/stringrenderer.cpp

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/**********************************************************************
* File: stringrenderer.cpp
* Description: Class for rendering UTF-8 text to an image, and retrieving
* bounding boxes around each grapheme cluster.
* Author: Ranjith Unnikrishnan
* Created: Mon Nov 18 2013
*
* (C) Copyright 2013, Google Inc.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
**********************************************************************/
#include "stringrenderer.h"
#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <map>
#include <utility>
#include <vector>
#include "allheaders.h" // from leptonica
#include "boxchar.h"
#include "ligature_table.h"
#include "normstrngs.h"
#include "pango/pango-font.h"
#include "pango/pango-glyph-item.h"
#include "tlog.h"
#include "unichar.h"
#include "unicode/uchar.h" // from libicu
#include "util.h"
#ifdef USE_STD_NAMESPACE
using std::map;
using std::max;
using std::min;
using std::swap;
#endif
namespace tesseract {
static const int kDefaultOutputResolution = 300;
// Word joiner (U+2060) inserted after letters in ngram mode, as per
// recommendation in http://unicode.org/reports/tr14/ to avoid line-breaks at
// hyphens and other non-alpha characters.
static const char* kWordJoinerUTF8 = "\u2060";
static const char32 kWordJoiner = 0x2060;
static bool IsCombiner(int ch) {
const int char_type = u_charType(ch);
return ((char_type == U_NON_SPACING_MARK) ||
(char_type == U_ENCLOSING_MARK) ||
(char_type == U_COMBINING_SPACING_MARK));
}
static string EncodeAsUTF8(const char32 ch32) {
UNICHAR uni_ch(ch32);
return string(uni_ch.utf8(), uni_ch.utf8_len());
}
// Returns true with probability 'prob'.
static bool RandBool(const double prob, TRand* rand) {
if (prob == 1.0) return true;
if (prob == 0.0) return false;
return rand->UnsignedRand(1.0) < prob;
}
/* static */
Pix* CairoARGB32ToPixFormat(cairo_surface_t *surface) {
if (cairo_image_surface_get_format(surface) != CAIRO_FORMAT_ARGB32) {
printf("Unexpected surface format %d\n",
cairo_image_surface_get_format(surface));
return NULL;
}
const int width = cairo_image_surface_get_width(surface);
const int height = cairo_image_surface_get_height(surface);
Pix* pix = pixCreate(width, height, 32);
int byte_stride = cairo_image_surface_get_stride(surface);
for (int i = 0; i < height; ++i) {
memcpy(reinterpret_cast<unsigned char*>(pix->data + i * pix->wpl) + 1,
cairo_image_surface_get_data(surface) + i * byte_stride,
byte_stride - ((i == height - 1) ? 1 : 0));
}
return pix;
}
StringRenderer::StringRenderer(const string& font_desc, int page_width,
int page_height)
: page_width_(page_width),
page_height_(page_height),
h_margin_(50),
v_margin_(50),
char_spacing_(0),
leading_(0),
vertical_text_(false),
gravity_hint_strong_(false),
render_fullwidth_latin_(false),
underline_start_prob_(0),
underline_continuation_prob_(0),
underline_style_(PANGO_UNDERLINE_SINGLE),
drop_uncovered_chars_(true),
strip_unrenderable_words_(false),
add_ligatures_(false),
output_word_boxes_(false),
surface_(NULL),
cr_(NULL),
layout_(NULL),
start_box_(0),
page_(0),
box_padding_(0),
total_chars_(0),
font_index_(0),
last_offset_(0) {
pen_color_[0] = 0.0;
pen_color_[1] = 0.0;
pen_color_[2] = 0.0;
set_font(font_desc);
set_resolution(kDefaultOutputResolution);
page_boxes_ = NULL;
}
bool StringRenderer::set_font(const string& desc) {
bool success = font_.ParseFontDescriptionName(desc);
font_.set_resolution(resolution_);
return success;
}
void StringRenderer::set_resolution(const int resolution) {
resolution_ = resolution;
font_.set_resolution(resolution);
}
void StringRenderer::set_underline_start_prob(const double frac) {
underline_start_prob_ = min(max(frac, 0.0), 1.0);
}
void StringRenderer::set_underline_continuation_prob(const double frac) {
underline_continuation_prob_ = min(max(frac, 0.0), 1.0);
}
StringRenderer::~StringRenderer() {
ClearBoxes();
FreePangoCairo();
}
void StringRenderer::InitPangoCairo() {
FreePangoCairo();
surface_ = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, page_width_,
page_height_);
cr_ = cairo_create(surface_);
{
DISABLE_HEAP_LEAK_CHECK;
layout_ = pango_cairo_create_layout(cr_);
}
if (vertical_text_) {
PangoContext* context = pango_layout_get_context(layout_);
pango_context_set_base_gravity(context, PANGO_GRAVITY_EAST);
if (gravity_hint_strong_) {
pango_context_set_gravity_hint(context, PANGO_GRAVITY_HINT_STRONG);
}
pango_layout_context_changed(layout_);
}
SetLayoutProperties();
}
void StringRenderer::SetLayoutProperties() {
string font_desc = font_.DescriptionName();
// Specify the font via a description name
PangoFontDescription *desc =
pango_font_description_from_string(font_desc.c_str());
// Assign the font description to the layout
pango_layout_set_font_description(layout_, desc);
pango_font_description_free(desc); // free the description
pango_cairo_context_set_resolution(pango_layout_get_context(layout_),
resolution_);
int max_width = page_width_ - 2 * h_margin_;
int max_height = page_height_ - 2 * v_margin_;
tlog(3, "max_width = %d, max_height = %d\n", max_width, max_height);
if (vertical_text_) {
swap(max_width, max_height);
}
pango_layout_set_width(layout_, max_width * PANGO_SCALE);
pango_layout_set_wrap(layout_, PANGO_WRAP_WORD);
// Adjust character spacing
PangoAttrList* attr_list = pango_attr_list_new();
if (char_spacing_) {
PangoAttribute* spacing_attr = pango_attr_letter_spacing_new(
static_cast<int>(char_spacing_ * PANGO_SCALE + 0.5));
spacing_attr->start_index = 0;
spacing_attr->end_index = static_cast<guint>(-1);
pango_attr_list_change(attr_list, spacing_attr);
}
pango_layout_set_attributes(layout_, attr_list);
pango_attr_list_unref(attr_list);
// Adjust line spacing
if (leading_) {
pango_layout_set_spacing(layout_, leading_ * PANGO_SCALE);
}
}
void StringRenderer::FreePangoCairo() {
if (layout_) {
g_object_unref(layout_);
layout_ = NULL;
}
if (cr_) {
cairo_destroy(cr_);
cr_ = NULL;
}
if (surface_) {
cairo_surface_destroy(surface_);
surface_ = NULL;
}
}
void StringRenderer::SetWordUnderlineAttributes(const string& page_text) {
if (underline_start_prob_ == 0) return;
PangoAttrList* attr_list = pango_layout_get_attributes(layout_);
const char* text = page_text.c_str();
int offset = 0;
TRand rand;
bool started_underline = false;
PangoAttribute* und_attr = nullptr;
while (offset < page_text.length()) {
offset += SpanUTF8Whitespace(text + offset);
if (offset == page_text.length()) break;
int word_start = offset;
int word_len = SpanUTF8NotWhitespace(text + offset);
offset += word_len;
if (started_underline) {
// Should we continue the underline to the next word?
if (RandBool(underline_continuation_prob_, &rand)) {
// Continue the current underline to this word.
und_attr->end_index = word_start + word_len;
} else {
// Otherwise end the current underline attribute at the end of the
// previous word.
pango_attr_list_insert(attr_list, und_attr);
started_underline = false;
und_attr = nullptr;
}
}
if (!started_underline && RandBool(underline_start_prob_, &rand)) {
// Start a new underline attribute
und_attr = pango_attr_underline_new(underline_style_);
und_attr->start_index = word_start;
und_attr->end_index = word_start + word_len;
started_underline = true;
}
}
// Finish the current underline attribute at the end of the page.
if (started_underline) {
und_attr->end_index = page_text.length();
pango_attr_list_insert(attr_list, und_attr);
}
}
// Returns offset in utf8 bytes to first page.
int StringRenderer::FindFirstPageBreakOffset(const char* text,
int text_length) {
if (!text_length) return 0;
const int max_height = (page_height_ - 2 * v_margin_);
const int max_width = (page_width_ - 2 * h_margin_);
const int max_layout_height = vertical_text_ ? max_width : max_height;
UNICHAR::const_iterator it = UNICHAR::begin(text, text_length);
const UNICHAR::const_iterator it_end = UNICHAR::end(text, text_length);
const int kMaxUnicodeBufLength = 15000;
for (int i = 0; i < kMaxUnicodeBufLength && it != it_end; ++it, ++i);
int buf_length = it.utf8_data() - text;
tlog(1, "len = %d buf_len = %d\n", text_length, buf_length);
pango_layout_set_text(layout_, text, buf_length);
PangoLayoutIter* line_iter = NULL;
{ // Fontconfig caches some info here that is not freed before exit.
DISABLE_HEAP_LEAK_CHECK;
line_iter = pango_layout_get_iter(layout_);
}
bool first_page = true;
int page_top = 0;
int offset = buf_length;
do {
// Get bounding box of the current line
PangoRectangle line_ink_rect;
pango_layout_iter_get_line_extents(line_iter, &line_ink_rect, NULL);
pango_extents_to_pixels(&line_ink_rect, NULL);
PangoLayoutLine* line = pango_layout_iter_get_line_readonly(line_iter);
if (first_page) {
page_top = line_ink_rect.y;
first_page = false;
}
int line_bottom = line_ink_rect.y + line_ink_rect.height;
if (line_bottom - page_top > max_layout_height) {
offset = line->start_index;
tlog(1, "Found offset = %d\n", offset);
break;
}
} while (pango_layout_iter_next_line(line_iter));
pango_layout_iter_free(line_iter);
return offset;
}
const vector<BoxChar*>& StringRenderer::GetBoxes() const {
return boxchars_;
}
Boxa* StringRenderer::GetPageBoxes() const {
return page_boxes_;
}
void StringRenderer::RotatePageBoxes(float rotation) {
BoxChar::RotateBoxes(rotation, page_width_ / 2, page_height_ / 2,
start_box_, boxchars_.size(), &boxchars_);
}
void StringRenderer::ClearBoxes() {
for (int i = 0; i < boxchars_.size(); ++i)
delete boxchars_[i];
boxchars_.clear();
boxaDestroy(&page_boxes_);
}
void StringRenderer::WriteAllBoxes(const string& filename) {
BoxChar::PrepareToWrite(&boxchars_);
BoxChar::WriteTesseractBoxFile(filename, page_height_, boxchars_);
}
// Returns cluster strings in logical order.
bool StringRenderer::GetClusterStrings(vector<string>* cluster_text) {
map<int, string> start_byte_to_text;
PangoLayoutIter* run_iter = pango_layout_get_iter(layout_);
const char* full_text = pango_layout_get_text(layout_);
do {
PangoLayoutRun* run = pango_layout_iter_get_run_readonly(run_iter);
if (!run) {
// End of line NULL run marker
tlog(2, "Found end of line marker\n");
continue;
}
PangoGlyphItemIter cluster_iter;
gboolean have_cluster;
for (have_cluster = pango_glyph_item_iter_init_start(&cluster_iter,
run, full_text);
have_cluster;
have_cluster = pango_glyph_item_iter_next_cluster(&cluster_iter)) {
const int start_byte_index = cluster_iter.start_index;
const int end_byte_index = cluster_iter.end_index;
string text = string(full_text + start_byte_index,
end_byte_index - start_byte_index);
if (IsUTF8Whitespace(text.c_str())) {
tlog(2, "Found whitespace\n");
text = " ";
}
tlog(2, "start_byte=%d end_byte=%d : '%s'\n", start_byte_index,
end_byte_index, text.c_str());
if (add_ligatures_) {
// Make sure the output box files have ligatured text in case the font
// decided to use an unmapped glyph.
text = LigatureTable::Get()->AddLigatures(text, NULL);
}
start_byte_to_text[start_byte_index] = text;
}
} while (pango_layout_iter_next_run(run_iter));
pango_layout_iter_free(run_iter);
cluster_text->clear();
for (map<int, string>::const_iterator it = start_byte_to_text.begin();
it != start_byte_to_text.end(); ++it) {
cluster_text->push_back(it->second);
}
return cluster_text->size();
}
// Merges an array of BoxChars into words based on the identification of
// BoxChars containing the space character as inter-word separators.
//
// Sometime two adjacent characters in the sequence may be detected as lying on
// different lines based on their spatial positions. This may be the result of a
// newline character at end of the last word on a line in the source text, or of
// a discretionary line-break created by Pango at intra-word locations like
// hyphens. When this is detected the word is split at that location into
// multiple BoxChars. Otherwise, each resulting BoxChar will contain a word and
// its bounding box.
static void MergeBoxCharsToWords(vector<BoxChar*>* boxchars) {
vector<BoxChar*> result;
bool started_word = false;
for (int i = 0; i < boxchars->size(); ++i) {
if (boxchars->at(i)->ch() == " " ||
boxchars->at(i)->box() == NULL) {
result.push_back(boxchars->at(i));
boxchars->at(i) = NULL;
started_word = false;
continue;
}
if (!started_word) {
// Begin new word
started_word = true;
result.push_back(boxchars->at(i));
boxchars->at(i) = NULL;
} else {
BoxChar* last_boxchar = result.back();
// Compute bounding box union
const Box* box = boxchars->at(i)->box();
Box* last_box = last_boxchar->mutable_box();
int left = min(last_box->x, box->x);
int right = max(last_box->x + last_box->w, box->x + box->w);
int top = min(last_box->y, box->y);
int bottom = max(last_box->y + last_box->h, box->y + box->h);
// Conclude that the word was broken to span multiple lines based on the
// size of the merged bounding box in relation to those of the individual
// characters seen so far.
if (right - left > last_box->w + 5 * box->w) {
tlog(1, "Found line break after '%s'", last_boxchar->ch().c_str());
// Insert a fake interword space and start a new word with the current
// boxchar.
result.push_back(new BoxChar(" ", 1));
result.push_back(boxchars->at(i));
boxchars->at(i) = NULL;
continue;
}
// Append to last word
last_boxchar->mutable_ch()->append(boxchars->at(i)->ch());
last_box->x = left;
last_box->w = right - left;
last_box->y = top;
last_box->h = bottom - top;
delete boxchars->at(i);
boxchars->at(i) = NULL;
}
}
boxchars->swap(result);
}
void StringRenderer::ComputeClusterBoxes() {
const char* text = pango_layout_get_text(layout_);
PangoLayoutIter* cluster_iter = pango_layout_get_iter(layout_);
// Do a first pass to store cluster start indexes.
vector<int> cluster_start_indices;
do {
cluster_start_indices.push_back(pango_layout_iter_get_index(cluster_iter));
tlog(3, "Added %d\n", cluster_start_indices.back());
} while (pango_layout_iter_next_cluster(cluster_iter));
pango_layout_iter_free(cluster_iter);
cluster_start_indices.push_back(strlen(text));
tlog(3, "Added last index %d\n", cluster_start_indices.back());
// Sort the indices and create a map from start to end indices.
sort(cluster_start_indices.begin(), cluster_start_indices.end());
map<int, int> cluster_start_to_end_index;
for (int i = 0; i < cluster_start_indices.size() - 1; ++i) {
cluster_start_to_end_index[cluster_start_indices[i]]
= cluster_start_indices[i + 1];
}
// Iterate again to compute cluster boxes and their text with the obtained
// cluster extent information.
cluster_iter = pango_layout_get_iter(layout_);
// Store BoxChars* sorted by their byte start positions
map<int, BoxChar*> start_byte_to_box;
do {
PangoRectangle cluster_rect;
pango_layout_iter_get_cluster_extents(cluster_iter, &cluster_rect,
NULL);
pango_extents_to_pixels(&cluster_rect, NULL);
const int start_byte_index = pango_layout_iter_get_index(cluster_iter);
const int end_byte_index = cluster_start_to_end_index[start_byte_index];
string cluster_text = string(text + start_byte_index,
end_byte_index - start_byte_index);
if (cluster_text.size() && cluster_text[0] == '\n') {
tlog(2, "Skipping newlines at start of text.\n");
continue;
}
if (!cluster_rect.width || !cluster_rect.height ||
IsUTF8Whitespace(cluster_text.c_str())) {
tlog(2, "Skipping whitespace with boxdim (%d,%d) '%s'\n",
cluster_rect.width, cluster_rect.height, cluster_text.c_str());
BoxChar* boxchar = new BoxChar(" ", 1);
boxchar->set_page(page_);
start_byte_to_box[start_byte_index] = boxchar;
continue;
}
// Prepare a boxchar for addition at this byte position.
tlog(2, "[%d %d], %d, %d : start_byte=%d end_byte=%d : '%s'\n",
cluster_rect.x, cluster_rect.y,
cluster_rect.width, cluster_rect.height,
start_byte_index, end_byte_index,
cluster_text.c_str());
ASSERT_HOST_MSG(cluster_rect.width,
"cluster_text:%s start_byte_index:%d\n",
cluster_text.c_str(), start_byte_index);
ASSERT_HOST_MSG(cluster_rect.height,
"cluster_text:%s start_byte_index:%d\n",
cluster_text.c_str(), start_byte_index);
if (box_padding_) {
cluster_rect.x = max(0, cluster_rect.x - box_padding_);
cluster_rect.width += 2 * box_padding_;
cluster_rect.y = max(0, cluster_rect.y - box_padding_);
cluster_rect.height += 2 * box_padding_;
}
if (add_ligatures_) {
// Make sure the output box files have ligatured text in case the font
// decided to use an unmapped glyph.
cluster_text = LigatureTable::Get()->AddLigatures(cluster_text, NULL);
}
BoxChar* boxchar = new BoxChar(cluster_text.c_str(), cluster_text.size());
boxchar->set_page(page_);
boxchar->AddBox(cluster_rect.x, cluster_rect.y,
cluster_rect.width, cluster_rect.height);
start_byte_to_box[start_byte_index] = boxchar;
} while (pango_layout_iter_next_cluster(cluster_iter));
pango_layout_iter_free(cluster_iter);
// There is a subtle bug in the cluster text reported by the PangoLayoutIter
// on ligatured characters (eg. The word "Lam-Aliph" in arabic). To work
// around this, we use text reported using the PangoGlyphIter which is
// accurate.
// TODO(ranjith): Revisit whether this is still needed in newer versions of
// pango.
vector<string> cluster_text;
if (GetClusterStrings(&cluster_text)) {
ASSERT_HOST(cluster_text.size() == start_byte_to_box.size());
int ind = 0;
for (map<int, BoxChar*>::iterator it = start_byte_to_box.begin();
it != start_byte_to_box.end(); ++it, ++ind) {
it->second->mutable_ch()->swap(cluster_text[ind]);
}
}
// Append to the boxchars list in byte order.
vector<BoxChar*> page_boxchars;
page_boxchars.reserve(start_byte_to_box.size());
string last_ch;
for (map<int, BoxChar*>::const_iterator it = start_byte_to_box.begin();
it != start_byte_to_box.end(); ++it) {
if (it->second->ch() == kWordJoinerUTF8) {
// Skip zero-width joiner characters (ZWJs) here.
delete it->second;
} else {
page_boxchars.push_back(it->second);
}
}
CorrectBoxPositionsToLayout(&page_boxchars);
if (render_fullwidth_latin_) {
for (map<int, BoxChar*>::iterator it = start_byte_to_box.begin();
it != start_byte_to_box.end(); ++it) {
// Convert fullwidth Latin characters to their halfwidth forms.
string half(ConvertFullwidthLatinToBasicLatin(it->second->ch()));
it->second->mutable_ch()->swap(half);
}
}
// Merge the character boxes into word boxes if we are rendering n-grams.
if (output_word_boxes_) {
MergeBoxCharsToWords(&page_boxchars);
}
boxchars_.insert(boxchars_.end(), page_boxchars.begin(), page_boxchars.end());
// Compute the page bounding box
Box* page_box = NULL;
Boxa* all_boxes = NULL;
for (int i = 0; i < page_boxchars.size(); ++i) {
if (page_boxchars[i]->box() == NULL) continue;
if (all_boxes == NULL)
all_boxes = boxaCreate(0);
boxaAddBox(all_boxes, page_boxchars[i]->mutable_box(), L_CLONE);
}
boxaGetExtent(all_boxes, NULL, NULL, &page_box);
boxaDestroy(&all_boxes);
if (page_boxes_ == NULL)
page_boxes_ = boxaCreate(0);
boxaAddBox(page_boxes_, page_box, L_INSERT);
}
void StringRenderer::CorrectBoxPositionsToLayout(vector<BoxChar*>* boxchars) {
if (vertical_text_) {
const double rotation = - pango_gravity_to_rotation(
pango_context_get_base_gravity(pango_layout_get_context(layout_)));
BoxChar::TranslateBoxes(page_width_ - h_margin_, v_margin_, boxchars);
BoxChar::RotateBoxes(rotation, page_width_ - h_margin_, v_margin_,
0, boxchars->size(), boxchars);
} else {
BoxChar::TranslateBoxes(h_margin_, v_margin_, boxchars);
}
}
int StringRenderer::StripUnrenderableWords(string* utf8_text) const {
string output_text;
const char* text = utf8_text->c_str();
int offset = 0;
int num_dropped = 0;
while (offset < utf8_text->length()) {
int space_len = SpanUTF8Whitespace(text + offset);
output_text.append(text + offset, space_len);
offset += space_len;
if (offset == utf8_text->length()) break;
int word_len = SpanUTF8NotWhitespace(text + offset);
if (font_.CanRenderString(text + offset, word_len)) {
output_text.append(text + offset, word_len);
} else {
++num_dropped;
}
offset += word_len;
}
utf8_text->swap(output_text);
if (num_dropped > 0) {
tprintf("Stripped %d unrenderable words\n", num_dropped);
}
return num_dropped;
}
int StringRenderer::RenderToGrayscaleImage(const char* text, int text_length,
Pix** pix) {
Pix *orig_pix = NULL;
int offset = RenderToImage(text, text_length, &orig_pix);
if (orig_pix) {
*pix = pixConvertTo8(orig_pix, false);
pixDestroy(&orig_pix);
}
return offset;
}
int StringRenderer::RenderToBinaryImage(const char* text, int text_length,
int threshold, Pix** pix) {
Pix *orig_pix = NULL;
int offset = RenderToImage(text, text_length, &orig_pix);
if (orig_pix) {
Pix* gray_pix = pixConvertTo8(orig_pix, false);
pixDestroy(&orig_pix);
*pix = pixThresholdToBinary(gray_pix, threshold);
pixDestroy(&gray_pix);
} else {
*pix = orig_pix;
}
return offset;
}
// Add word joiner (WJ) characters between adjacent non-space characters except
// immediately before a combiner.
/* static */
string StringRenderer::InsertWordJoiners(const string& text) {
string out_str;
const UNICHAR::const_iterator it_end = UNICHAR::end(text.c_str(),
text.length());
for (UNICHAR::const_iterator it = UNICHAR::begin(text.c_str(), text.length());
it != it_end; ++it) {
// Add the symbol to the output string.
out_str.append(it.utf8_data(), it.utf8_len());
// Check the next symbol.
UNICHAR::const_iterator next_it = it;
++next_it;
bool next_char_is_boundary = (next_it == it_end || *next_it == ' ');
bool next_char_is_combiner = (next_it == it_end) ?
false : IsCombiner(*next_it);
if (*it != ' ' && *it != '\n' && !next_char_is_boundary &&
!next_char_is_combiner) {
out_str += kWordJoinerUTF8;
}
}
return out_str;
}
// Convert halfwidth Basic Latin characters to their fullwidth forms.
string StringRenderer::ConvertBasicLatinToFullwidthLatin(const string& str) {
string full_str;
const UNICHAR::const_iterator it_end = UNICHAR::end(str.c_str(),
str.length());
for (UNICHAR::const_iterator it = UNICHAR::begin(str.c_str(), str.length());
it != it_end; ++it) {
// Convert printable and non-space 7-bit ASCII characters to
// their fullwidth forms.
if (IsInterchangeValid7BitAscii(*it) && isprint(*it) && !isspace(*it)) {
// Convert by adding 0xFEE0 to the codepoint of 7-bit ASCII.
char32 full_char = *it + 0xFEE0;
full_str.append(EncodeAsUTF8(full_char));
} else {
full_str.append(it.utf8_data(), it.utf8_len());
}
}
return full_str;
}
// Convert fullwidth Latin characters to their halfwidth forms.
string StringRenderer::ConvertFullwidthLatinToBasicLatin(const string& str) {
string half_str;
UNICHAR::const_iterator it_end = UNICHAR::end(str.c_str(), str.length());
for (UNICHAR::const_iterator it = UNICHAR::begin(str.c_str(), str.length());
it != it_end; ++it) {
char32 half_char = FullwidthToHalfwidth(*it);
// Convert fullwidth Latin characters to their halfwidth forms
// only if halfwidth forms are printable and non-space 7-bit ASCII.
if (IsInterchangeValid7BitAscii(half_char) &&
isprint(half_char) && !isspace(half_char)) {
half_str.append(EncodeAsUTF8(half_char));
} else {
half_str.append(it.utf8_data(), it.utf8_len());
}
}
return half_str;
}
// Returns offset to end of text substring rendered in this method.
int StringRenderer::RenderToImage(const char* text, int text_length,
Pix** pix) {
if (pix && *pix) pixDestroy(pix);
InitPangoCairo();
const int page_offset = FindFirstPageBreakOffset(text, text_length);
if (!page_offset) {
return 0;
}
start_box_ = boxchars_.size();
if (!vertical_text_) {
// Translate by the specified margin
cairo_translate(cr_, h_margin_, v_margin_);
} else {
// Vertical text rendering is achieved by a two-step process of first
// performing regular horizontal layout with character orientation set to
// EAST, and then translating and rotating the layout before rendering onto
// the desired image surface. The settings required for the former step are
// done within InitPangoCairo().
//
// Translate to the top-right margin of page
cairo_translate(cr_, page_width_ - h_margin_, v_margin_);
// Rotate the layout
double rotation = - pango_gravity_to_rotation(
pango_context_get_base_gravity(pango_layout_get_context(layout_)));
tlog(2, "Rotating by %f radians\n", rotation);
cairo_rotate(cr_, rotation);
pango_cairo_update_layout(cr_, layout_);
}
string page_text(text, page_offset);
if (render_fullwidth_latin_) {
// Convert Basic Latin to their fullwidth forms.
page_text = ConvertBasicLatinToFullwidthLatin(page_text);
}
if (strip_unrenderable_words_) {
StripUnrenderableWords(&page_text);
}
if (drop_uncovered_chars_ &&
!font_.CoversUTF8Text(page_text.c_str(), page_text.length())) {
int num_dropped = font_.DropUncoveredChars(&page_text);
if (num_dropped) {
tprintf("WARNING: Dropped %d uncovered characters\n", num_dropped);
}
}
if (add_ligatures_) {
// Add ligatures wherever possible, including custom ligatures.
page_text = LigatureTable::Get()->AddLigatures(page_text, &font_);
}
if (underline_start_prob_ > 0) {
SetWordUnderlineAttributes(page_text);
}
pango_layout_set_text(layout_, page_text.c_str(), page_text.length());
if (pix) {
// Set a white background for the target image surface.
cairo_set_source_rgb(cr_, 1.0, 1.0, 1.0); // sets drawing colour to white
// Fill the surface with the active colour (if you don't do this, you will
// be given a surface with a transparent background to draw on)
cairo_paint(cr_);
// Set the ink color to black
cairo_set_source_rgb(cr_, pen_color_[0], pen_color_[1], pen_color_[2]);
// If the target surface or transformation properties of the cairo instance
// have changed, update the pango layout to reflect this
pango_cairo_update_layout(cr_, layout_);
{
DISABLE_HEAP_LEAK_CHECK; // for Fontconfig
// Draw the pango layout onto the cairo surface
pango_cairo_show_layout(cr_, layout_);
}
*pix = CairoARGB32ToPixFormat(surface_);
}
ComputeClusterBoxes();
FreePangoCairo();
// Update internal state variables.
++page_;
return page_offset;
}
// Render a string to an image, returning it as an 8 bit pix. Behaves as
// RenderString, except that it ignores the font set at construction and works
// through all the fonts, returning 0 until they are exhausted, at which point
// it returns the value it should have returned all along, but no pix this time.
// Fonts that don't contain a given proportion of the characters in the string
// get skipped.
// Fonts that work each get rendered and the font name gets added
// to the image.
// NOTE that no boxes are produced by this function.
//
// Example usage: To render a null terminated char-array "txt"
//
// int offset = 0;
// do {
// Pix *pix;
// offset += renderer.RenderAllFontsToImage(min_proportion, txt + offset,
// strlen(txt + offset), NULL, &pix);
// ...
// } while (offset < strlen(text));
//
int StringRenderer::RenderAllFontsToImage(double min_coverage,
const char* text, int text_length,
string* font_used, Pix** image) {
*image = NULL;
// Select a suitable font to render the title with.
const char kTitleTemplate[] = "%s : %d hits = %.2f%%, raw = %d = %.2f%%";
string title_font;
if (!FontUtils::SelectFont(kTitleTemplate, strlen(kTitleTemplate),
&title_font, NULL)) {
tprintf("WARNING: Could not find a font to render image title with!\n");
title_font = "Arial";
}
title_font += " 8";
tlog(1, "Selected title font: %s\n", title_font.c_str());
if (font_used) font_used->clear();
string orig_font = font_.DescriptionName();
if (char_map_.empty()) {
total_chars_ = 0;
// Fill the hash table and use that for computing which fonts to use.
for (UNICHAR::const_iterator it = UNICHAR::begin(text, text_length);
it != UNICHAR::end(text, text_length); ++it) {
++total_chars_;
++char_map_[*it];
}
tprintf("Total chars = %d\n", total_chars_);
}
const vector<string>& all_fonts = FontUtils::ListAvailableFonts();
for (int i = font_index_; i < all_fonts.size(); ++i) {
++font_index_;
int raw_score = 0;
int ok_chars = FontUtils::FontScore(char_map_, all_fonts[i], &raw_score,
NULL);
if (ok_chars > 0 && ok_chars >= total_chars_ * min_coverage) {
set_font(all_fonts[i]);
int offset = RenderToBinaryImage(text, text_length, 128, image);
ClearBoxes(); // Get rid of them as they are garbage.
const int kMaxTitleLength = 1024;
char title[kMaxTitleLength];
snprintf(title, kMaxTitleLength, kTitleTemplate,
all_fonts[i].c_str(), ok_chars,
100.0 * ok_chars / total_chars_, raw_score,
100.0 * raw_score / char_map_.size());
tprintf("%s\n", title);
// This is a good font! Store the offset to return once we've tried all
// the fonts.
if (offset) {
last_offset_ = offset;
if (font_used) *font_used = all_fonts[i];
}
// Add the font to the image.
set_font(title_font);
v_margin_ /= 8;
Pix* title_image = NULL;
RenderToBinaryImage(title, strlen(title), 128, &title_image);
pixOr(*image, *image, title_image);
pixDestroy(&title_image);
v_margin_ *= 8;
set_font(orig_font);
// We return the real offset only after cycling through the list of fonts.
return 0;
} else {
tprintf("Font %s failed with %d hits = %.2f%%\n",
all_fonts[i].c_str(), ok_chars, 100.0 * ok_chars / total_chars_);
}
}
font_index_ = 0;
char_map_.clear();
return last_offset_ == 0 ? -1 : last_offset_;
}
} // namespace tesseract
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