view layer/ImageRegionFinder.cpp @ 317:e251c3599ea8

* Make RemoteFile far more pervasive, and use it for local files as well
  so that we can handle both transparently.  Make it shallow copy with
  reference counting, so it can be used by value without having to worry
  about the cache file lifetime.  Use RemoteFile for MainWindow file-open
  functions, etc

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2007 QMUL.
    
    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; either version 2 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.
*/

#include "ImageRegionFinder.h"

#include <QImage>
#include <cmath>
#include <stack>
#include <iostream>

ImageRegionFinder::ImageRegionFinder()
{
}

ImageRegionFinder::~ImageRegionFinder()
{
}

QRect
ImageRegionFinder::findRegionExtents(QImage *image, QPoint origin) const
{
    int w = image->width(), h = image->height();

    QImage visited(w, h, QImage::Format_Mono);
    visited.fill(0);

    std::stack<QPoint> s;
    s.push(origin);

    int xmin = origin.x();
    int xmax = xmin;
    int ymin = origin.y();
    int ymax = ymin;

    QRgb opix = image->pixel(origin);

    while (!s.empty()) {

        QPoint p = s.top();
        s.pop();

        visited.setPixel(p, 1);

        int x = p.x(), y = p.y();

        if (x < xmin) xmin = x;
        if (x > xmax) xmax = x;

        if (y < ymin) ymin = y;
        if (y > ymax) ymax = y;

        std::stack<QPoint> neighbours;

        int similarNeighbourCount = 0;

        for (int dx = -1; dx <= 1; ++dx) {
            for (int dy = -1; dy <= 1; ++dy) {

                if ((dx != 0 && dy != 0) ||
                    (dx == 0 && dy == 0)) 
                    continue;

                if (x + dx < 0 || x + dx >= w ||
                    y + dy < 0 || y + dy >= h)
                    continue;

                if (visited.pixelIndex(x + dx, y + dy) != 0)
                    continue;

                if (!similar(opix, image->pixel(x + dx, y + dy))) 
                    continue;

                neighbours.push(QPoint(x + dx, y + dy));
                ++similarNeighbourCount;
            }
        }

        if (similarNeighbourCount >= 2) {
            while (!neighbours.empty()) {
                s.push(neighbours.top());
                neighbours.pop();
            }
        }
    }

    return QRect(xmin, ymin, xmax - xmin, ymax - ymin);
}

bool
ImageRegionFinder::similar(QRgb a, QRgb b) const
{
    if (b == qRgb(0, 0, 0) || b == qRgb(255, 255, 255)) {
        // black and white are boundary cases, don't compare similar
        // to anything -- not even themselves
        return false;
    }

    float ar = float(qRed(a) / 255.f);
    float ag = float(qGreen(a) / 255.f);
    float ab = float(qBlue(a) / 255.f);
    float amag = sqrtf(ar * ar + ag * ag + ab * ab);
    float thresh = amag / 2;

    float dr = float(qRed(a) - qRed(b)) / 255.f;
    float dg = float(qGreen(a) - qGreen(b)) / 255.f;
    float db = float(qBlue(a) - qBlue(b)) / 255.f;
    float dist = sqrtf(dr * dr + dg * dg + db * db);

//    std::cerr << "thresh=" << thresh << ", dist=" << dist << std::endl;

    return (dist < thresh);
}