/******************************************************************************

 ** Filename:    normfeat.c

 ** Purpose:     Definition of char normalization features.

 ** Author:      Dan Johnson

 **

 ** (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 "normfeat.h"

#include "featdefs.h"

#include "intfx.h"

#include "mfoutline.h"

namespace tesseract {

/** Return the length of the outline in baseline normalized form. */

float ActualOutlineLength(FEATURE Feature) {

  return (Feature->Params[CharNormLength] * LENGTH_COMPRESSION);

}

/**

 * Return the character normalization feature for a blob.

 *

 * The features returned are in a scale where the x-height has been

 * normalized to live in the region y = [-0.25 .. 0.25].  Example ranges

 * for English below are based on the Linux font collection on 2009-12-04:

 *

 *  - Params[CharNormY]

 *     - The y coordinate of the grapheme's centroid.

 *     - English: [-0.27, 0.71]

 *

 *  - Params[CharNormLength]

 *     - The length of the grapheme's outline (tiny segments discarded),

 *     divided by 10.0=LENGTH_COMPRESSION.

 *     - English: [0.16, 0.85]

 *

 *  - Params[CharNormRx]

 *     - The radius of gyration about the x axis, as measured from CharNormY.

 *     - English: [0.011, 0.34]

 *

 *  - Params[CharNormRy]

 *     - The radius of gyration about the y axis, as measured from

 *     the x center of the grapheme's bounding box.

 *     - English: [0.011, 0.31]

 */

FEATURE_SET ExtractCharNormFeatures(const INT_FX_RESULT_STRUCT &fx_info) {

  auto feature_set = new FEATURE_SET_STRUCT(1);

  auto feature = new FEATURE_STRUCT(&CharNormDesc);

  feature->Params[CharNormY] = MF_SCALE_FACTOR * (fx_info.Ymean - kBlnBaselineOffset);

  feature->Params[CharNormLength] = MF_SCALE_FACTOR * fx_info.Length / LENGTH_COMPRESSION;

  feature->Params[CharNormRx] = MF_SCALE_FACTOR * fx_info.Rx;

  feature->Params[CharNormRy] = MF_SCALE_FACTOR * fx_info.Ry;

  AddFeature(feature_set, feature);

  return feature_set;

} /* ExtractCharNormFeatures */

} // namespace tesseract