| /////////////////////////////////////////////////////////////////////// |
| // File: otsuthr.h |
| // Description: Simple Otsu thresholding for binarizing images. |
| // Author: Ray Smith |
| // Created: Fri Mar 07 12:14:01 PST 2008 |
| // |
| // (C) Copyright 2008, 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_CCMAIN_OTSUTHR_H__ |
| #define TESSERACT_CCMAIN_OTSUTHR_H__ |
| |
| namespace tesseract { |
| |
| const int kHistogramSize = 256; // The size of a histogram of pixel values. |
| |
| // Compute the Otsu threshold(s) for the given image rectangle, making one |
| // for each channel. Each channel is always one byte per pixel. |
| // Returns an array of threshold values and an array of hi_values, such |
| // that a pixel value >threshold[channel] is considered foreground if |
| // hi_values[channel] is 0 or background if 1. A hi_value of -1 indicates |
| // that there is no apparent foreground. At least one hi_value will not be -1. |
| // Delete thresholds and hi_values with delete [] after use. |
| void OtsuThreshold(const unsigned char* imagedata, |
| int bytes_per_pixel, int bytes_per_line, |
| int left, int top, int width, int height, |
| int** thresholds, int** hi_values); |
| |
| // Compute the histogram for the given image rectangle, and the given |
| // channel. (Channel pointed to by imagedata.) Each channel is always |
| // one byte per pixel. |
| // Bytes per pixel is used to skip channels not being |
| // counted with this call in a multi-channel (pixel-major) image. |
| // Histogram is always a 256 element array to count occurrences of |
| // each pixel value. |
| void HistogramRect(const unsigned char* imagedata, |
| int bytes_per_pixel, int bytes_per_line, |
| int left, int top, int width, int height, |
| int* histogram); |
| |
| // Compute the Otsu threshold(s) for the given histogram. |
| // Also returns H = total count in histogram, and |
| // omega0 = count of histogram below threshold. |
| int OtsuStats(const int* histogram, int* H_out, int* omega0_out); |
| |
| } // namespace tesseract. |
| |
| #endif // TESSERACT_CCMAIN_OTSUTHR_H__ |