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//=============================================================================
// MusE Reader
// Music Score Reader
//
// Copyright (C) 2010 Werner Schweer
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License version 2.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
//=============================================================================
#include "image.h"
#include "utils.h"
#include "omr.h"
#include "omrpage.h"
namespace Ms {
//=============================================================================
// inspired by ImageMagick (http://www.imagemagick.org)
//=============================================================================
// imageSkew() calculates skew of image. Skew is an artifact that
// occurs in scanned images because of the camera being misaligned,
// imperfections in the scanning or surface, or simply because the paper was
// not placed completely flat when scanned.
//
// The format of the imageSkew method is:
//
// double imageSkew(const QImage *image)
//
// Benchmark 7.3sec test2 first page
// 6
// 5.7
// 5.3
// 3.74
// 3.30
// 0.47sec RELEASE
#define MyPI 3.14159265358979323846264338327950288419716939937510
//---------------------------------------------------------
// RadiansToDegrees
//---------------------------------------------------------
static inline double RadiansToDegrees(double r) {
return 180.0 * r / MyPI;
}
//---------------------------------------------------------
// RadonInfo
//---------------------------------------------------------
class RadonInfo {
int size;
public:
ushort* cells;
int width, height;
RadonInfo(ulong w, ulong h) {
width = w;
height = h;
size = w * h;
cells = new ushort[size];
}
~RadonInfo() { delete[] cells; }
void reset() { memset(cells, 0, size * sizeof(*cells)); }
ushort getCell(int x, int y) const { return cells[height * x + y]; }
void setCell(int x, int y, ushort value) { cells[height * x + y] = value; }
};
//---------------------------------------------------------
// radonProjection
//---------------------------------------------------------
static void radonProjection(RadonInfo* src, RadonInfo* dst, int sign, ulong* projection)
{
RadonInfo* p = src;
RadonInfo* q = dst;
for (int step = 1; step < p->width; step *= 2) {
for (int x = 0; x < p->width; x += 2 * step) {
for (int i = 0; i < step; i++) {
int y;
for (y = 0; y < (p->height-i-1); y++) {
ushort cell = p->getCell(x+i, y);
q->setCell(x+2*i, y, cell + p->getCell(x+i+step, y+i));
q->setCell(x+2*i+1, y, cell + p->getCell(x+i+step, y+i+1));
}
for ( ; y < (p->height-i); y++) {
ushort cell = p->getCell(x+i, y);
q->setCell(x+2*i, y, cell + p->getCell(x+i+step, y+i));
q->setCell(x+2*i+1, y, cell);
}
for ( ; y < p->height; y++) {
ushort cell = p->getCell(x+i, y);
q->setCell(x+2*i, y, cell);
q->setCell(x+2*i+1, y, cell);
}
}
}
RadonInfo* swap = p;
p = q;
q = swap;
}
for (int x = 0; x < p->width; x++) {
uint sum = 0;
for (int y = 0; y < (p->height-1); y++) {
int delta = p->getCell(x, y) - p->getCell(x, y + 1);
sum += delta * delta;
}
projection[p->width + sign * x - 1] = sum;
}
}
//---------------------------------------------------------
// radonTransform
//---------------------------------------------------------
void OmrPage::radonTransform(ulong* projection, int w, int n, const QRect& r)
{
int h = r.height();
RadonInfo* src = new RadonInfo(w, h);
RadonInfo* dst = new RadonInfo(w, h);
src->reset();
for (int y = 0; y < h; y++) {
int i = n;
const uchar* p = (const uchar*)scanLine(r.y() + y);
for (int x = 0; x < n; ++x)
src->setCell(--i, y, Omr::bitsSetTable[*p++]);
}
radonProjection(src, dst, -1, projection);
src->reset();
for (int y = 0; y < h; y++) {
const uchar* p = (const uchar*)scanLine(r.y() + y);
for (int x = 0; x < n; ++x)
src->setCell(x, y, Omr::bitsSetTable[*p++]);
}
radonProjection(src, dst, 1, projection);
delete dst;
delete src;
}
//---------------------------------------------------------
// skew
// compute image skew angle
//---------------------------------------------------------
double OmrPage::skew(const QRect& r)
{
// Benchmark bench("imageSkew");
int nn = wordsPerLine() * 4;
int width = 1;
for (; width < nn; width <<= 1)
;
int n = 2 * width - 1;
ulong* projection = new ulong[n];
radonTransform(projection, width, nn, r);
uint max_projection = 0;
int skew = 0;
for (int i = 0; i < n; i++) {
if (projection[i] > max_projection) {
skew = i - width + 1;
max_projection = projection[i];
}
}
delete[] projection;
return RadiansToDegrees(-atan((double) skew/width/8));
}
}
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