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59 lines
2.6 KiB
C
59 lines
2.6 KiB
C
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///////////////////////////////////////////////////////////////////////
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// File: otsuthr.h
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// Description: Simple Otsu thresholding for binarizing images.
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// Author: Ray Smith
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// Created: Fri Mar 07 12:14:01 PST 2008
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//
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// (C) Copyright 2008, Google Inc.
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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///////////////////////////////////////////////////////////////////////
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#ifndef TESSERACT_CCMAIN_OTSUTHR_H__
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#define TESSERACT_CCMAIN_OTSUTHR_H__
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namespace tesseract {
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const int kHistogramSize = 256; // The size of a histogram of pixel values.
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// Compute the Otsu threshold(s) for the given image rectangle, making one
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// for each channel. Each channel is always one byte per pixel.
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// Returns an array of threshold values and an array of hi_values, such
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// that a pixel value >threshold[channel] is considered foreground if
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// hi_values[channel] is 0 or background if 1. A hi_value of -1 indicates
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// that there is no apparent foreground. At least one hi_value will not be -1.
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// Delete thresholds and hi_values with delete [] after use.
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void OtsuThreshold(const unsigned char* imagedata,
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int bytes_per_pixel, int bytes_per_line,
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int left, int top, int width, int height,
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int** thresholds, int** hi_values);
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// Compute the histogram for the given image rectangle, and the given
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// channel. (Channel pointed to by imagedata.) Each channel is always
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// one byte per pixel.
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// Bytes per pixel is used to skip channels not being
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// counted with this call in a multi-channel (pixel-major) image.
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// Histogram is always a 256 element array to count occurrences of
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// each pixel value.
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void HistogramRect(const unsigned char* imagedata,
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int bytes_per_pixel, int bytes_per_line,
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int left, int top, int width, int height,
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int* histogram);
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// Compute the Otsu threshold(s) for the given histogram.
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// Also returns H = total count in histogram, and
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// omega0 = count of histogram below threshold.
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int OtsuStats(const int* histogram, int* H_out, int* omega0_out);
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} // namespace tesseract.
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#endif // TESSERACT_CCMAIN_OTSUTHR_H__
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