comparison layer/ImageRegionFinder.cpp @ 283:86a112b5b319

* Make it possible to "measure" a feature on the spectrogram by double-
  clicking in measure mode
* Make shift-click-drag (for zoom to region) work in measure mode as well
  as navigate mode.  It would be nice to be able to shift-doubleclick to
  zoom on a feature directly using a combination of these last two features,
  but that isn't possible yet.
* Make Del delete the measurement under the mouse pointer.

+/* -*- 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);
+}
+