normalis.h

/**********************************************************************
 * File:        normalis.h  (Formerly denorm.h)
 * Description: Code for the DENORM class.
 * Author:      Ray Smith
 * Created:     Thu Apr 23 09:22:43 BST 1992
 *
 * (C) Copyright 1992, Hewlett-Packard Ltd.
 ** 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.
 *
 **********************************************************************/

#ifndef NORMALIS_H
#define NORMALIS_H

const int kBlnCellHeight = 256;     // Full-height for baseline normalization.
const int kBlnXHeight = 128;        // x-height for baseline normalization.
const int kBlnBaselineOffset = 64;  // offset for baseline normalization.

class BLOCK;
class FCOORD;
class TBOX;
class UNICHARSET;

struct Pix;
struct TBLOB;
struct TPOINT;

template <typename T> class GenericVector;

namespace tesseract {

// Possible normalization methods. Use NEGATIVE values as these also
// double up as markers for the last sub-classifier.
enum NormalizationMode {
  NM_BASELINE = -3,         // The original BL normalization mode.
  NM_CHAR_ISOTROPIC = -2,   // Character normalization but isotropic.
  NM_CHAR_ANISOTROPIC = -1  // The original CN normalization mode.
};

}  // namespace tesseract.

class DENORM {
 public:
  DENORM();

  // Copying a DENORM is allowed.
  DENORM(const DENORM &);
  DENORM& operator=(const DENORM&);
  ~DENORM();

  // Setup the normalization transformation parameters.
  // The normalizations applied to a blob are as follows:
  // 1. An optional block layout rotation that was applied during layout
  // analysis to make the textlines horizontal.
  // 2. A normalization transformation (LocalNormTransform):
  // Subtract the "origin"
  // Apply an x,y scaling.
  // Apply an optional rotation.
  // Add back a final translation.
  // The origin is in the block-rotated space, and is usually something like
  // the x-middle of the word at the baseline.
  // 3. Zero or more further normalization transformations that are applied
  // in sequence, with a similar pattern to the first normalization transform.
  //
  // A DENORM holds the parameters of a single normalization, and can execute
  // both the LocalNormTransform (a forwards normalization), and the
  // LocalDenormTransform which is an inverse transform or de-normalization.
  // A DENORM may point to a predecessor DENORM, which is actually the earlier
  // normalization, so the full normalization sequence involves executing all
  // predecessors first and then the transform in "this".
  // Let x be image co-ordinates and that we have normalization classes A, B, C
  // where we first apply A then B then C to get normalized x':
  // x' = CBAx
  // Then the backwards (to original coordinates) would be:
  // x = A^-1 B^-1 C^-1 x'
  // and A = B->predecessor_ and B = C->predecessor_
  // NormTransform executes all predecessors recursively, and then this.
  // NormTransform would be used to transform an image-based feature to
  // normalized space for use in a classifier
  // DenormTransform inverts this and then all predecessors. It can be
  // used to get back to the original image coordinates from normalized space.
  // The LocalNormTransform member executes just the transformation
  // in "this" without the layout rotation or any predecessors. It would be
  // used to run each successive normalization, eg the word normalization,
  // and later the character normalization.

  // Arguments:
  // block: if not nullptr, then this is the first transformation, and
  //        block->re_rotation() needs to be used after the Denorm
  //        transformation to get back to the image coords.
  // rotation: if not nullptr, apply this rotation after translation to the
  //           origin and scaling. (Usually a classify rotation.)
  // predecessor: if not nullptr, then predecessor has been applied to the
  //              input space and needs to be undone to complete the inverse.
  // The above pointers are not owned by this DENORM and are assumed to live
  // longer than this denorm, except rotation, which is deep copied on input.
  //
  // x_origin: The x origin which will be mapped to final_xshift in the result.
  // y_origin: The y origin which will be mapped to final_yshift in the result.
  //           Added to result of row->baseline(x) if not nullptr.
  //
  // x_scale: scale factor for the x-coordinate.
  // y_scale: scale factor for the y-coordinate. Ignored if segs is given.
  // Note that these scale factors apply to the same x and y system as the
  // x-origin and y-origin apply, ie after any block rotation, but before
  // the rotation argument is applied.
  //
  // final_xshift: The x component of the final translation.
  // final_yshift: The y component of the final translation.
  //
  // In theory, any of the commonly used normalizations can be setup here:
  // * Traditional baseline normalization on a word:
  // SetupNormalization(block, nullptr, nullptr,
  //                    box.x_middle(), baseline,
  //                    kBlnXHeight / x_height, kBlnXHeight / x_height,
  //                    0, kBlnBaselineOffset);
  // * "Numeric mode" baseline normalization on a word, in which the blobs
  //   are positioned with the bottom as the baseline is achieved by making
  //   a separate DENORM for each blob.
  // SetupNormalization(block, nullptr, nullptr,
  //                    box.x_middle(), box.bottom(),
  //                    kBlnXHeight / x_height, kBlnXHeight / x_height,
  //                    0, kBlnBaselineOffset);
  // * Anisotropic character normalization used by IntFx.
  // SetupNormalization(nullptr, nullptr, denorm,
  //                    centroid_x, centroid_y,
  //                    51.2 / ry, 51.2 / rx, 128, 128);
  // * Normalize blob height to x-height (current OSD):
  // SetupNormalization(nullptr, &rotation, nullptr,
  //                    box.rotational_x_middle(rotation),
  //                    box.rotational_y_middle(rotation),
  //                    kBlnXHeight / box.rotational_height(rotation),
  //                    kBlnXHeight / box.rotational_height(rotation),
  //                    0, kBlnBaselineOffset);
  // * Secondary normalization for classification rotation (current):
  // FCOORD rotation = block->classify_rotation();
  // float target_height = kBlnXHeight / CCStruct::kXHeightCapRatio;
  // SetupNormalization(nullptr, &rotation, denorm,
  //                    box.rotational_x_middle(rotation),
  //                    box.rotational_y_middle(rotation),
  //                    target_height / box.rotational_height(rotation),
  //                    target_height / box.rotational_height(rotation),
  //                    0, kBlnBaselineOffset);
  // * Proposed new normalizations for CJK: Between them there is then
  // no need for further normalization at all, and the character fills the cell.
  // ** Replacement for baseline normalization on a word:
  // Scales height and width independently so that modal height and pitch
  // fill the cell respectively.
  // float cap_height = x_height / CCStruct::kXHeightCapRatio;
  // SetupNormalization(block, nullptr, nullptr,
  //                    box.x_middle(), cap_height / 2.0f,
  //                    kBlnCellHeight / fixed_pitch,
  //                    kBlnCellHeight / cap_height,
  //                    0, 0);
  // ** Secondary normalization for classification (with rotation) (proposed):
  // Requires a simple translation to the center of the appropriate character
  // cell, no further scaling and a simple rotation (or nothing) about the
  // cell center.
  // FCOORD rotation = block->classify_rotation();
  // SetupNormalization(nullptr, &rotation, denorm,
  //                    fixed_pitch_cell_center,
  //                    0.0f,
  //                    1.0f,
  //                    1.0f,
  //                    0, 0);
  void SetupNormalization(const BLOCK* block,
                          const FCOORD* rotation,
                          const DENORM* predecessor,
                          float x_origin, float y_origin,
                          float x_scale, float y_scale,
                          float final_xshift, float final_yshift);

  // Sets up the DENORM to execute a non-linear transformation based on
  // preserving an even distribution of stroke edges. The transformation
  // operates only within the given box, scaling input coords within the box
  // non-linearly to a box of target_width by target_height, with all other
  // coords being clipped to the box edge. As with SetupNormalization above,
  // final_xshift and final_yshift are applied after scaling, and the bottom-
  // left of box is used as a pre-scaling origin.
  // x_coords is a collection of the x-coords of vertical edges for each
  // y-coord starting at box.bottom().
  // y_coords is a collection of the y-coords of horizontal edges for each
  // x-coord starting at box.left().
  // Eg x_coords[0] is a collection of the x-coords of edges at y=bottom.
  // Eg x_coords[1] is a collection of the x-coords of edges at y=bottom + 1.
  // The second-level vectors must all be sorted in ascending order.
  void SetupNonLinear(const DENORM* predecessor, const TBOX& box,
                      float target_width, float target_height,
                      float final_xshift, float final_yshift,
                      const GenericVector<GenericVector<int> >& x_coords,
                      const GenericVector<GenericVector<int> >& y_coords);

  // Transforms the given coords one step forward to normalized space, without
  // using any block rotation or predecessor.
  void LocalNormTransform(const TPOINT& pt, TPOINT* transformed) const;
  void LocalNormTransform(const FCOORD& pt, FCOORD* transformed) const;
  // Transforms the given coords forward to normalized space using the
  // full transformation sequence defined by the block rotation, the
  // predecessors, deepest first, and finally this. If first_norm is not nullptr,
  // then the first and deepest transformation used is first_norm, ending
  // with this, and the block rotation will not be applied.
  void NormTransform(const DENORM* first_norm, const TPOINT& pt,
                     TPOINT* transformed) const;
  void NormTransform(const DENORM* first_norm, const FCOORD& pt,
                     FCOORD* transformed) const;
  // Transforms the given coords one step back to source space, without
  // using to any block rotation or predecessor.
  void LocalDenormTransform(const TPOINT& pt, TPOINT* original) const;
  void LocalDenormTransform(const FCOORD& pt, FCOORD* original) const;
  // Transforms the given coords all the way back to source image space using
  // the full transformation sequence defined by this and its predecessors
  // recursively, shallowest first, and finally any block re_rotation.
  // If last_denorm is not nullptr, then the last transformation used will
  // be last_denorm, and the block re_rotation will never be executed.
  void DenormTransform(const DENORM* last_denorm, const TPOINT& pt,
                       TPOINT* original) const;
  void DenormTransform(const DENORM* last_denorm, const FCOORD& pt,
                       FCOORD* original) const;

  // Normalize a blob using blob transformations. Less accurate, but
  // more accurately copies the old way.
  void LocalNormBlob(TBLOB* blob) const;

  // Fills in the x-height range accepted by the given unichar_id in blob
  // coordinates, given its bounding box in the usual baseline-normalized
  // coordinates, with some initial crude x-height estimate (such as word
  // size) and this denoting the transformation that was used.
  // Also returns the amount the character must have shifted up or down.
  void XHeightRange(int unichar_id, const UNICHARSET& unicharset,
                    const TBOX& bbox,
                    float* min_xht,
                    float* max_xht,
                    float* yshift) const;

  // Prints the content of the DENORM for debug purposes.
  void Print() const;

  Pix* pix() const {
    return pix_;
  }
  void set_pix(Pix* pix) {
    pix_ = pix;
  }
  bool inverse() const {
    return inverse_;
  }
  void set_inverse(bool value) {
    inverse_ = value;
  }
  const DENORM* RootDenorm() const {
    if (predecessor_ != nullptr)
      return predecessor_->RootDenorm();
    return this;
  }
  const DENORM* predecessor() const {
    return predecessor_;
  }
  // Accessors - perhaps should not be needed.
  float x_scale() const {
    return x_scale_;
  }
  float y_scale() const {
    return y_scale_;
  }
  const BLOCK* block() const {
    return block_;
  }
  void set_block(const BLOCK* block) {
    block_ = block;
  }

 private:
  // Free allocated memory and clear pointers.
  void Clear();
  // Setup default values.
  void Init();

  // Best available image.
  Pix* pix_;
  // True if the source image is white-on-black.
  bool inverse_;
  // Block the word came from. If not null, block->re_rotation() takes the
  // "untransformed" coordinates even further back to the original image.
  // Used only on the first DENORM in a chain.
  const BLOCK* block_;
  // Rotation to apply between translation to the origin and scaling.
  const FCOORD* rotation_;
  // Previous transformation in a chain.
  const DENORM* predecessor_;
  // Non-linear transformation maps directly from each integer offset from the
  // origin to the corresponding x-coord. Owned by the DENORM.
  GenericVector<float>* x_map_;
  // Non-linear transformation maps directly from each integer offset from the
  // origin to the corresponding y-coord. Owned by the DENORM.
  GenericVector<float>* y_map_;
  // x-coordinate to be mapped to final_xshift_ in the result.
  float x_origin_;
  // y-coordinate to be mapped to final_yshift_ in the result.
  float y_origin_;
  // Scale factors for x and y coords. Applied to pre-rotation system.
  float x_scale_;
  float y_scale_;
  // Destination coords of the x_origin_ and y_origin_.
  float final_xshift_;
  float final_yshift_;
};

#endif