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/*
* Copyright (C) 2005 - 2015 René Rebe
* (C) 2005 - 2007 Archivista GmbH, CH-8042 Zuerich
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2. A copy of the GNU General
* Public License can be found in the file LICENSE.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANT-
* ABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
* Public License for more details.
*
* Alternatively, commercial licensing options are available from the
* copyright holder ExactCODE GmbH Germany.
*/
#include <iostream>
#include "Bits.hh"
#include "Image.hh"
#include "Colorspace.hh"
#include "Matrix.hh"
#include "empty-page.hh"
#include "optimize2bw.hh"
/* TODO: for more accurance one could introduce a hot-spot area that
has a higher weight than the other (outer) region to more reliably
detect crossed but otherwise empty pages */
bool detect_empty_page (Image& im, double percent, int marginH, int marginV,
int* set_pixels)
{
// sanitize margins
if (marginH % 8 != 0)
marginH -= marginH % 8;
Image* image, img;
if (im.spp == 1 && im.bps == 1) {
image = &im;
}
// already in sub-byte domain? just count the black pixels
else if (im.spp == 1 && im.bps < 8) {
img = im; image = &img;
colorspace_by_name (*image, "gray1");
}
// if not 1-bit, yet: convert it down ...
else {
img = im; image = &img;
// don't care about cmyk vs. rgb, just get gray8 pixels, quickly
colorspace_by_name (*image, "gray8");
// force quick pass, no color use, 1px radius
optimize2bw (*image, 0/*min*/, 0/*max*/, 128/*thr*/, 0/*sloppy*/, 1/*radius*/);
// convert to 1-bit (threshold) - optimize2bw does not perform that step ...
colorspace_gray8_to_gray1 (*image);
}
const int stride = image->stride();
const int stridefill = image->stridefill();
// count pixels by table lookup
int pixels = 0;
uint8_t* data = image->getRawData();
for (int row = marginV; row < image->h - marginV; ++row)
{
uint8_t* rowptr = data + stride * row;
for (int x = marginH/8; x < stridefill - marginH/8; ++x) {
int b = Exact::popcount[rowptr[x]];
// it is a bitsset table - and we want the zeros ...
pixels += 8-b;
}
}
float image_percent = 100.0 * pixels / (image->w * image->h);
if (set_pixels)
*set_pixels = pixels;
return image_percent < percent;
}
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