/****************************************************************************** ** Filename: intfx.c ** Purpose: Integer character normalization & feature extraction ** Author: Robert Moss, rays@google.com (Ray Smith) ** History: Tue May 21 15:51:57 MDT 1991, RWM, Created. ** Tue Feb 28 10:42:00 PST 2012, vastly rewritten to allow greyscale fx and non-linear normalization. ** ** (c) Copyright Hewlett-Packard Company, 1988. ** 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 Files and Type Defines ----------------------------------------------------------------------------**/ #include "intfx.h" #include "allheaders.h" #include "ccutil.h" #include "classify.h" #include "const.h" #include "helpers.h" #include "intmatcher.h" #include "linlsq.h" #include "ndminx.h" #include "normalis.h" #include "statistc.h" #include "trainingsample.h" using tesseract::TrainingSample; /**---------------------------------------------------------------------------- Global Data Definitions and Declarations ----------------------------------------------------------------------------**/ // Look up table for cos and sin to turn the intfx feature angle to a vector. // Protected by atan_table_mutex. // The entries are in binary degrees where a full circle is 256 binary degrees. static float cos_table[INT_CHAR_NORM_RANGE]; static float sin_table[INT_CHAR_NORM_RANGE]; // Guards write access to AtanTable so we don't create it more than once. tesseract::CCUtilMutex atan_table_mutex; /**---------------------------------------------------------------------------- Public Code ----------------------------------------------------------------------------**/ /*---------------------------------------------------------------------------*/ void InitIntegerFX() { static bool atan_table_init = false; atan_table_mutex.Lock(); if (!atan_table_init) { for (int i = 0; i < INT_CHAR_NORM_RANGE; ++i) { cos_table[i] = cos(i * 2 * PI / INT_CHAR_NORM_RANGE + PI); sin_table[i] = sin(i * 2 * PI / INT_CHAR_NORM_RANGE + PI); } atan_table_init = true; } atan_table_mutex.Unlock(); } // Returns a vector representing the direction of a feature with the given // theta direction in an INT_FEATURE_STRUCT. FCOORD FeatureDirection(uinT8 theta) { return FCOORD(cos_table[theta], sin_table[theta]); } namespace tesseract { // Generates a TrainingSample from a TBLOB. Extracts features and sets // the bounding box, so classifiers that operate on the image can work. // TODO(rays) Make BlobToTrainingSample a member of Classify now that // the FlexFx and FeatureDescription code have been removed and LearnBlob // is now a member of Classify. TrainingSample* BlobToTrainingSample( const TBLOB& blob, bool nonlinear_norm, INT_FX_RESULT_STRUCT* fx_info, GenericVector* bl_features) { GenericVector cn_features; Classify::ExtractFeatures(blob, nonlinear_norm, bl_features, &cn_features, fx_info, NULL); // TODO(rays) Use blob->PreciseBoundingBox() instead. TBOX box = blob.bounding_box(); TrainingSample* sample = NULL; int num_features = fx_info->NumCN; if (num_features > 0) { sample = TrainingSample::CopyFromFeatures(*fx_info, box, &cn_features[0], num_features); } if (sample != NULL) { // Set the bounding box (in original image coordinates) in the sample. TPOINT topleft, botright; topleft.x = box.left(); topleft.y = box.top(); botright.x = box.right(); botright.y = box.bottom(); TPOINT original_topleft, original_botright; blob.denorm().DenormTransform(NULL, topleft, &original_topleft); blob.denorm().DenormTransform(NULL, botright, &original_botright); sample->set_bounding_box(TBOX(original_topleft.x, original_botright.y, original_botright.x, original_topleft.y)); } return sample; } // Computes the DENORMS for bl(baseline) and cn(character) normalization // during feature extraction. The input denorm describes the current state // of the blob, which is usually a baseline-normalized word. // The Transforms setup are as follows: // Baseline Normalized (bl) Output: // We center the grapheme by aligning the x-coordinate of its centroid with // x=128 and leaving the already-baseline-normalized y as-is. // // Character Normalized (cn) Output: // We align the grapheme's centroid at the origin and scale it // asymmetrically in x and y so that the 2nd moments are a standard value // (51.2) ie the result is vaguely square. // If classify_nonlinear_norm is true: // A non-linear normalization is setup that attempts to evenly distribute // edges across x and y. // // Some of the fields of fx_info are also setup: // Length: Total length of outline. // Rx: Rounded y second moment. (Reversed by convention.) // Ry: rounded x second moment. // Xmean: Rounded x center of mass of the blob. // Ymean: Rounded y center of mass of the blob. void Classify::SetupBLCNDenorms(const TBLOB& blob, bool nonlinear_norm, DENORM* bl_denorm, DENORM* cn_denorm, INT_FX_RESULT_STRUCT* fx_info) { // Compute 1st and 2nd moments of the original outline. FCOORD center, second_moments; int length = blob.ComputeMoments(¢er, &second_moments); if (fx_info != NULL) { fx_info->Length = length; fx_info->Rx = IntCastRounded(second_moments.y()); fx_info->Ry = IntCastRounded(second_moments.x()); fx_info->Xmean = IntCastRounded(center.x()); fx_info->Ymean = IntCastRounded(center.y()); } // Setup the denorm for Baseline normalization. bl_denorm->SetupNormalization(NULL, NULL, &blob.denorm(), center.x(), 128.0f, 1.0f, 1.0f, 128.0f, 128.0f); // Setup the denorm for character normalization. if (nonlinear_norm) { GenericVector > x_coords; GenericVector > y_coords; TBOX box; blob.GetPreciseBoundingBox(&box); box.pad(1, 1); blob.GetEdgeCoords(box, &x_coords, &y_coords); cn_denorm->SetupNonLinear(&blob.denorm(), box, MAX_UINT8, MAX_UINT8, 0.0f, 0.0f, x_coords, y_coords); } else { cn_denorm->SetupNormalization(NULL, NULL, &blob.denorm(), center.x(), center.y(), 51.2f / second_moments.x(), 51.2f / second_moments.y(), 128.0f, 128.0f); } } // Helper normalizes the direction, assuming that it is at the given // unnormed_pos, using the given denorm, starting at the root_denorm. uinT8 NormalizeDirection(uinT8 dir, const FCOORD& unnormed_pos, const DENORM& denorm, const DENORM* root_denorm) { // Convert direction to a vector. FCOORD unnormed_end; unnormed_end.from_direction(dir); unnormed_end += unnormed_pos; FCOORD normed_pos, normed_end; denorm.NormTransform(root_denorm, unnormed_pos, &normed_pos); denorm.NormTransform(root_denorm, unnormed_end, &normed_end); normed_end -= normed_pos; return normed_end.to_direction(); } // Helper returns the mean direction vector from the given stats. Use the // mean direction from dirs if there is information available, otherwise, use // the fit_vector from point_diffs. static FCOORD MeanDirectionVector(const LLSQ& point_diffs, const LLSQ& dirs, const FCOORD& start_pt, const FCOORD& end_pt) { FCOORD fit_vector; if (dirs.count() > 0) { // There were directions, so use them. To avoid wrap-around problems, we // have 2 accumulators in dirs: x for normal directions and y for // directions offset by 128. We will use the one with the least variance. FCOORD mean_pt = dirs.mean_point(); double mean_dir = 0.0; if (dirs.x_variance() <= dirs.y_variance()) { mean_dir = mean_pt.x(); } else { mean_dir = mean_pt.y() + 128; } fit_vector.from_direction(Modulo(IntCastRounded(mean_dir), 256)); } else { // There were no directions, so we rely on the vector_fit to the points. // Since the vector_fit is 180 degrees ambiguous, we align with the // supplied feature_dir by making the scalar product non-negative. FCOORD feature_dir(end_pt - start_pt); fit_vector = point_diffs.vector_fit(); if (fit_vector.x() == 0.0f && fit_vector.y() == 0.0f) { // There was only a single point. Use feature_dir directly. fit_vector = feature_dir; } else { // Sometimes the least mean squares fit is wrong, due to the small sample // of points and scaling. Use a 90 degree rotated vector if that matches // feature_dir better. FCOORD fit_vector2 = !fit_vector; // The fit_vector is 180 degrees ambiguous, so resolve the ambiguity by // insisting that the scalar product with the feature_dir should be +ve. if (fit_vector % feature_dir < 0.0) fit_vector = -fit_vector; if (fit_vector2 % feature_dir < 0.0) fit_vector2 = -fit_vector2; // Even though fit_vector2 has a higher mean squared error, it might be // a better fit, so use it if the dot product with feature_dir is bigger. if (fit_vector2 % feature_dir > fit_vector % feature_dir) fit_vector = fit_vector2; } } return fit_vector; } // Helper computes one or more features corresponding to the given points. // Emitted features are on the line defined by: // start_pt + lambda * (end_pt - start_pt) for scalar lambda. // Features are spaced at feature_length intervals. static int ComputeFeatures(const FCOORD& start_pt, const FCOORD& end_pt, double feature_length, GenericVector* features) { FCOORD feature_vector(end_pt - start_pt); if (feature_vector.x() == 0.0f && feature_vector.y() == 0.0f) return 0; // Compute theta for the feature based on its direction. uinT8 theta = feature_vector.to_direction(); // Compute the number of features and lambda_step. double target_length = feature_vector.length(); int num_features = IntCastRounded(target_length / feature_length); if (num_features == 0) return 0; // Divide the length evenly into num_features pieces. double lambda_step = 1.0 / num_features; double lambda = lambda_step / 2.0; for (int f = 0; f < num_features; ++f, lambda += lambda_step) { FCOORD feature_pt(start_pt); feature_pt += feature_vector * lambda; INT_FEATURE_STRUCT feature(feature_pt, theta); features->push_back(feature); } return num_features; } // Gathers outline points and their directions from start_index into dirs by // stepping along the outline and normalizing the coordinates until the // required feature_length has been collected or end_index is reached. // On input pos must point to the position corresponding to start_index and on // return pos is updated to the current raw position, and pos_normed is set to // the normed version of pos. // Since directions wrap-around, they need special treatment to get the mean. // Provided the cluster of directions doesn't straddle the wrap-around point, // the simple mean works. If they do, then, unless the directions are wildly // varying, the cluster rotated by 180 degrees will not straddle the wrap- // around point, so mean(dir + 180 degrees) - 180 degrees will work. Since // LLSQ conveniently stores the mean of 2 variables, we use it to store // dir and dir+128 (128 is 180 degrees) and then use the resulting mean // with the least variance. static int GatherPoints(const C_OUTLINE* outline, double feature_length, const DENORM& denorm, const DENORM* root_denorm, int start_index, int end_index, ICOORD* pos, FCOORD* pos_normed, LLSQ* points, LLSQ* dirs) { int step_length = outline->pathlength(); ICOORD step = outline->step(start_index % step_length); // Prev_normed is the start point of this collection and will be set on the // first iteration, and on later iterations used to determine the length // that has been collected. FCOORD prev_normed; points->clear(); dirs->clear(); int num_points = 0; int index; for (index = start_index; index <= end_index; ++index, *pos += step) { step = outline->step(index % step_length); int edge_weight = outline->edge_strength_at_index(index % step_length); if (edge_weight == 0) { // This point has conflicting gradient and step direction, so ignore it. continue; } // Get the sub-pixel precise location and normalize. FCOORD f_pos = outline->sub_pixel_pos_at_index(*pos, index % step_length); denorm.NormTransform(root_denorm, f_pos, pos_normed); if (num_points == 0) { // The start of this segment. prev_normed = *pos_normed; } else { FCOORD offset = *pos_normed - prev_normed; float length = offset.length(); if (length > feature_length) { // We have gone far enough from the start. We will use this point in // the next set so return what we have so far. return index; } } points->add(pos_normed->x(), pos_normed->y(), edge_weight); int direction = outline->direction_at_index(index % step_length); if (direction >= 0) { direction = NormalizeDirection(direction, f_pos, denorm, root_denorm); // Use both the direction and direction +128 so we are not trying to // take the mean of something straddling the wrap-around point. dirs->add(direction, Modulo(direction + 128, 256)); } ++num_points; } return index; } // Extracts Tesseract features and appends them to the features vector. // Startpt to lastpt, inclusive, MUST have the same src_outline member, // which may be NULL. The vector from lastpt to its next is included in // the feature extraction. Hidden edges should be excluded by the caller. // If force_poly is true, the features will be extracted from the polygonal // approximation even if more accurate data is available. static void ExtractFeaturesFromRun( const EDGEPT* startpt, const EDGEPT* lastpt, const DENORM& denorm, double feature_length, bool force_poly, GenericVector* features) { const EDGEPT* endpt = lastpt->next; const C_OUTLINE* outline = startpt->src_outline; if (outline != NULL && !force_poly) { // Detailed information is available. We have to normalize only from // the root_denorm to denorm. const DENORM* root_denorm = denorm.RootDenorm(); int total_features = 0; // Get the features from the outline. int step_length = outline->pathlength(); int start_index = startpt->start_step; // pos is the integer coordinates of the binary image steps. ICOORD pos = outline->position_at_index(start_index); // We use an end_index that allows us to use a positive increment, but that // may be beyond the bounds of the outline steps/ due to wrap-around, to // so we use % step_length everywhere, except for start_index. int end_index = lastpt->start_step + lastpt->step_count; if (end_index <= start_index) end_index += step_length; LLSQ prev_points; LLSQ prev_dirs; FCOORD prev_normed_pos = outline->sub_pixel_pos_at_index(pos, start_index); denorm.NormTransform(root_denorm, prev_normed_pos, &prev_normed_pos); LLSQ points; LLSQ dirs; FCOORD normed_pos; int index = GatherPoints(outline, feature_length, denorm, root_denorm, start_index, end_index, &pos, &normed_pos, &points, &dirs); while (index <= end_index) { // At each iteration we nominally have 3 accumulated sets of points and // dirs: prev_points/dirs, points/dirs, next_points/dirs and sum them // into sum_points/dirs, but we don't necessarily get any features out, // so if that is the case, we keep accumulating instead of rotating the // accumulators. LLSQ next_points; LLSQ next_dirs; FCOORD next_normed_pos; index = GatherPoints(outline, feature_length, denorm, root_denorm, index, end_index, &pos, &next_normed_pos, &next_points, &next_dirs); LLSQ sum_points(prev_points); // TODO(rays) find out why it is better to use just dirs and next_dirs // in sum_dirs, instead of using prev_dirs as well. LLSQ sum_dirs(dirs); sum_points.add(points); sum_points.add(next_points); sum_dirs.add(next_dirs); bool made_features = false; // If we have some points, we can try making some features. if (sum_points.count() > 0) { // We have gone far enough from the start. Make a feature and restart. FCOORD fit_pt = sum_points.mean_point(); FCOORD fit_vector = MeanDirectionVector(sum_points, sum_dirs, prev_normed_pos, normed_pos); // The segment to which we fit features is the line passing through // fit_pt in direction of fit_vector that starts nearest to // prev_normed_pos and ends nearest to normed_pos. FCOORD start_pos = prev_normed_pos.nearest_pt_on_line(fit_pt, fit_vector); FCOORD end_pos = normed_pos.nearest_pt_on_line(fit_pt, fit_vector); // Possible correction to match the adjacent polygon segment. if (total_features == 0 && startpt != endpt) { FCOORD poly_pos(startpt->pos.x, startpt->pos.y); denorm.LocalNormTransform(poly_pos, &start_pos); } if (index > end_index && startpt != endpt) { FCOORD poly_pos(endpt->pos.x, endpt->pos.y); denorm.LocalNormTransform(poly_pos, &end_pos); } int num_features = ComputeFeatures(start_pos, end_pos, feature_length, features); if (num_features > 0) { // We made some features so shuffle the accumulators. prev_points = points; prev_dirs = dirs; prev_normed_pos = normed_pos; points = next_points; dirs = next_dirs; made_features = true; total_features += num_features; } // The end of the next set becomes the end next time around. normed_pos = next_normed_pos; } if (!made_features) { // We didn't make any features, so keep the prev accumulators and // add the next ones into the current. points.add(next_points); dirs.add(next_dirs); } } } else { // There is no outline, so we are forced to use the polygonal approximation. const EDGEPT* pt = startpt; do { FCOORD start_pos(pt->pos.x, pt->pos.y); FCOORD end_pos(pt->next->pos.x, pt->next->pos.y); denorm.LocalNormTransform(start_pos, &start_pos); denorm.LocalNormTransform(end_pos, &end_pos); ComputeFeatures(start_pos, end_pos, feature_length, features); } while ((pt = pt->next) != endpt); } } // Extracts sets of 3-D features of length kStandardFeatureLength (=12.8), as // (x,y) position and angle as measured counterclockwise from the vector // <-1, 0>, from blob using two normalizations defined by bl_denorm and // cn_denorm. See SetpuBLCNDenorms for definitions. // If outline_cn_counts is not NULL, on return it contains the cumulative // number of cn features generated for each outline in the blob (in order). // Thus after the first outline, there were (*outline_cn_counts)[0] features, // after the second outline, there were (*outline_cn_counts)[1] features etc. void Classify::ExtractFeatures(const TBLOB& blob, bool nonlinear_norm, GenericVector* bl_features, GenericVector* cn_features, INT_FX_RESULT_STRUCT* results, GenericVector* outline_cn_counts) { DENORM bl_denorm, cn_denorm; tesseract::Classify::SetupBLCNDenorms(blob, nonlinear_norm, &bl_denorm, &cn_denorm, results); if (outline_cn_counts != NULL) outline_cn_counts->truncate(0); // Iterate the outlines. for (TESSLINE* ol = blob.outlines; ol != NULL; ol = ol->next) { // Iterate the polygon. EDGEPT* loop_pt = ol->FindBestStartPt(); EDGEPT* pt = loop_pt; if (pt == NULL) continue; do { if (pt->IsHidden()) continue; // Find a run of equal src_outline. EDGEPT* last_pt = pt; do { last_pt = last_pt->next; } while (last_pt != loop_pt && !last_pt->IsHidden() && last_pt->src_outline == pt->src_outline); last_pt = last_pt->prev; // Until the adaptive classifier can be weaned off polygon segments, // we have to force extraction from the polygon for the bl_features. ExtractFeaturesFromRun(pt, last_pt, bl_denorm, kStandardFeatureLength, true, bl_features); ExtractFeaturesFromRun(pt, last_pt, cn_denorm, kStandardFeatureLength, false, cn_features); pt = last_pt; } while ((pt = pt->next) != loop_pt); if (outline_cn_counts != NULL) outline_cn_counts->push_back(cn_features->size()); } results->NumBL = bl_features->size(); results->NumCN = cn_features->size(); results->YBottom = blob.bounding_box().bottom(); results->YTop = blob.bounding_box().top(); results->Width = blob.bounding_box().width(); } } // namespace tesseract /*--------------------------------------------------------------------------*/ // Extract a set of standard-sized features from Blobs and write them out in // two formats: baseline normalized and character normalized. // // We presume the Blobs are already scaled so that x-height=128 units // // Standard Features: // We take all outline segments longer than 7 units and chop them into // standard-sized segments of approximately 13 = (64 / 5) units. // When writing these features out, we output their center and angle as // measured counterclockwise from the vector <-1, 0> // // Baseline Normalized Output: // We center the grapheme by aligning the x-coordinate of its centroid with // x=0 and subtracting 128 from the y-coordinate. // // Character Normalized Output: // We align the grapheme's centroid at the origin and scale it asymmetrically // in x and y so that the result is vaguely square. // // Deprecated! Prefer tesseract::Classify::ExtractFeatures instead. bool ExtractIntFeat(const TBLOB& blob, bool nonlinear_norm, INT_FEATURE_ARRAY baseline_features, INT_FEATURE_ARRAY charnorm_features, INT_FX_RESULT_STRUCT* results) { GenericVector bl_features; GenericVector cn_features; tesseract::Classify::ExtractFeatures(blob, nonlinear_norm, &bl_features, &cn_features, results, NULL); if (bl_features.empty() || cn_features.empty() || bl_features.size() > MAX_NUM_INT_FEATURES || cn_features.size() > MAX_NUM_INT_FEATURES) { return false; // Feature extraction failed. } memcpy(baseline_features, &bl_features[0], bl_features.size() * sizeof(bl_features[0])); memcpy(charnorm_features, &cn_features[0], cn_features.size() * sizeof(cn_features[0])); return true; }