view layer/ImageRegionFinder.cpp @ 1534:bfd8b22fd67c

Fix #1904 Scrolling colour 3d plot does not always work when in View normalisation mode. We shouldn't imagine we've just invalidated the cache if the truth is that we've only just created the renderer

/* -*- 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);

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

    return (dist < thresh);
}