degradeimage.h

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/**********************************************************************
 * File:        degradeimage.h
 * Description: Function to degrade an image (usually of text) as if it
 *              has been printed and then scanned.
 * Authors:     Ray Smith
 *
 * (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.
 *
 **********************************************************************/
#ifndef TESSERACT_TRAINING_DEGRADEIMAGE_H_
#define TESSERACT_TRAINING_DEGRADEIMAGE_H_
 
#include <allheaders.h>
#include "helpers.h" // For TRand.
#include "rect.h"
 
namespace tesseract {
 
// Degrade the pix as if by a print/copy/scan cycle with exposure > 0
// corresponding to darkening on the copier and <0 lighter and 0 not copied.
// If rotation is not nullptr, the clockwise rotation in radians is saved there.
// The input pix must be 8 bit grey. (Binary with values 0 and 255 is OK.)
// The input image is destroyed and a different image returned.
Image DegradeImage(Image input, int exposure, TRand *randomizer, float *rotation);
 
// Creates and returns a Pix distorted by various means according to the bool
// flags. If boxes is not nullptr, the boxes are resized/positioned according to
// any spatial distortion and also by the integer reduction factor box_scale
// so they will match what the network will output.
// Returns nullptr on error. The returned Pix must be pixDestroyed.
Image PrepareDistortedPix(const Image pix, bool perspective, bool invert, bool white_noise,
                         bool smooth_noise, bool blur, int box_reduction, TRand *randomizer,
                         std::vector<TBOX> *boxes);
// Distorts anything that has a non-null pointer with the same pseudo-random
// perspective distortion. Width and height only need to be set if there
// is no pix. If there is a pix, then they will be taken from there.
void GeneratePerspectiveDistortion(int width, int height, TRand *randomizer, Image *pix,
                                   std::vector<TBOX> *boxes);
// Computes the coefficients of a randomized projective transformation.
// The image transform requires backward transformation coefficient, and the
// box transform the forward coefficients.
// Returns the incolor arg to pixProjective.
int ProjectiveCoeffs(int width, int height, TRand *randomizer, float **im_coeffs,
                     float **box_coeffs);
 
} // namespace tesseract
 
#endif // TESSERACT_TRAINING_DEGRADEIMAGE_H_