From ba4c49dfef1380f6a5d84129561dc24466c15fa1 Mon Sep 17 00:00:00 2001
From: Mark Jenkinson <mark@fmrib.ox.ac.uk>
Date: Thu, 9 Nov 2000 17:49:06 +0000
Subject: [PATCH] Implemented efficient sort
---
cluster.cc | 72 ++++++++++++++++++++++++++++--------------------------
1 file changed, 37 insertions(+), 35 deletions(-)
diff --git a/cluster.cc b/cluster.cc
index dc03caf..4daa402 100644
--- a/cluster.cc
+++ b/cluster.cc
@@ -9,17 +9,18 @@
#include "fmribmain.h"
#include "newimageall.h"
#include <vector>
+#include <algorithm>
using namespace NEWIMAGE;
void print_usage(char *argv[])
{
cerr << "Usage: " << argv[0] << " <input file> <output file> "
- << "<threshold> <output_format> [-fe]" << endl;
+ << "<threshold> <output_format> [options]" << endl;
cerr << "[-f] : threshold is fractional (of robust range) instead of "
<< "absolute"<<endl;
- cerr << "[-e] : used only edge connections (6-way) instead of "
- << "corner connections (26-way)"<<endl;
+ cerr << "[-6,18,26] : number of connections at each point (default is 26)"
+ <<endl;
cerr << "If threshold is -ve then binarization is inverted"<<endl;
cerr << "Output formats: the output intensity signifies:"<<endl;
cerr << "0 - size"<<endl;
@@ -67,21 +68,19 @@ void get_stats(const volume<int>& labelim, const volume<T>& origim,
void get_sizeorder(const std::vector<int>& size, std::vector<int>& sizeorder)
{
- // A BAD O(N^2) SORTING ALGORITHM...
- int labelnum=size.size()-1, maxidx=0, maxsize=0;
- sizeorder.resize(labelnum,0);
- std::vector<int> sizecopy(size);
- for (int n=labelnum; n>=1; n--) {
- maxidx=0;
- maxsize=0;
- for (int m=1; m<=labelnum; m++) {
- if (sizecopy[m]>maxsize) {
- maxidx = m;
- maxsize = sizecopy[m];
- }
- }
- sizecopy[maxidx]=0;
- sizeorder[maxidx] = n;
+ // find order of labels so that sizes are in *ascending* order
+ int length=size.size()-1;
+ std::vector<pair<int, int> > sortlist(length+1);
+ for (int n=0; n<=length; n++) {
+ sortlist[n] = pair<int, int>(size[n],n);
+ }
+ sortlist[0].first = 0; // force the background component to be in 0th posn
+ sort(sortlist.begin(),sortlist.end()); // O(N.log(N))
+
+ // second part of pair is now the prior-index of the sorted values
+ sizeorder.resize(length+1,0);
+ for (int n=0; n<=length; n++) {
+ sizeorder[sortlist[n].second] = n; // maps old index to new
}
}
@@ -113,29 +112,32 @@ int fmrib_main(int argc, char *argv[])
volume<T> vin;
read_volume(vin,argv[1]);
- // threshold the volume
- bool invert=false;
- float th;
- string opt1="", opt2="", opt="";
- if (argc>=6) { opt = argv[5]; }
- if (opt=="-f") { opt1="-f"; }
- else if (opt=="-e") { opt2="-e"; }
- else if ( (opt=="-fe") || (opt=="-ef") ) { opt1="-f"; opt2="-e"; }
- else if (opt!="") {
- cerr << "Unrecognised option "<<opt<<endl<<endl;
- print_usage(argv);
- return -1;
+ // parse the options
+ bool invert=false, fractionalthresh=false;
+ int numconnected=26;
+
+ for (int n=5; n<argc; n++) {
+ string opt=argv[n];
+ if (opt=="-f") { fractionalthresh=true; }
+ else if (opt=="-6") { numconnected=6; }
+ else if (opt=="-18") { numconnected=18; }
+ else if (opt=="-26") { numconnected=26; }
+ else {
+ cerr << "Unrecognised option "<<opt<<endl<<endl;
+ print_usage(argv);
+ return -1;
+ }
}
- bool use_corners=true;
- if (opt2=="-e") { use_corners=false; }
-
+ // threshold the volume
+ float th;
th = atof(argv[3]);
if (th<0.0) {
invert=true;
th=-th;
}
- if ( opt1=="-f" ) {
+
+ if ( fractionalthresh ) {
float frac = th;
th = frac*(vin.robustmax() - vin.robustmin()) + vin.robustmin();
}
@@ -143,7 +145,7 @@ int fmrib_main(int argc, char *argv[])
if (invert) { vin = ((T) 1) - vin; }
// Find the connected components
- labelim = connected_components(vin,use_corners);
+ labelim = connected_components(vin,numconnected);
// process according to the output format
read_volume(vin,argv[1]); // re-read the original volume
--
GitLab