001 /**
002 *
003 */
004 package org.wdssii.core;
005
006 import org.apache.commons.logging.Log;
007 import org.apache.commons.logging.LogFactory;
008
009 import ucar.ma2.ArrayFloat;
010 import ucar.ma2.ArrayInt;
011 import ucar.ma2.ArrayShort;
012
013 /**
014 * @author lakshman
015 *
016 */
017 public class NetcdfSparseGrid {
018 private ArrayShort pixelx;
019 private ArrayShort pixely;
020 private ArrayInt pixelcount;
021 private ArrayFloat values;
022 private static Log log = LogFactory.getLog(NetcdfSparseGrid.class);
023 public NetcdfSparseGrid(float[][] inValues, float backgroundValue){
024 int xdim = inValues.length;
025 int ydim = inValues[0].length;
026 // find the number of runs in sparse array
027 int N = 0;
028 boolean inRun = false;
029 float prevValue = backgroundValue;
030 for (int i=0; i < xdim; ++i){
031 for (int j=0; j < ydim; ++j){
032 if (inRun){
033 if (inValues[i][j] == backgroundValue ){
034 inRun = false;
035 }
036 else if (inValues[i][j] != prevValue){
037 prevValue = inValues[i][j];
038 ++N;
039 }
040 } else if (inValues[i][j] != backgroundValue){
041 prevValue = inValues[i][j];
042 ++N;
043 inRun = true;
044 }
045 }
046 }
047 if (log.isDebugEnabled()){
048 log.debug("SparseGrid compression reduced size of grid from " + (xdim*ydim) + " to " + N);
049 }
050
051 // special processing for N=0 since netcdf has problems with zero-length arrays
052 boolean zeroN = (N == 0);
053 if (zeroN){
054 N = 1;
055 }
056
057 // create sparse grid array
058 pixelx = new ArrayShort(new int[]{N});
059 pixely = new ArrayShort(new int[]{N});
060 pixelcount = new ArrayInt(new int[]{N});
061 values = new ArrayFloat(new int[]{N});
062
063 if (zeroN){
064 pixelx.set(pixelx.getIndex(), (short)0);
065 pixely.set(pixely.getIndex(), (short)0);
066 pixelcount.set(pixelcount.getIndex(),1);
067 values.set(values.getIndex(),backgroundValue);
068 return;
069 }
070
071 N = -1;
072 ucar.ma2.Index nIndex = pixelx.getIndex();
073 inRun = false;
074 prevValue = backgroundValue;
075 for (short i=0; i < xdim; ++i){
076 for (short j=0; j < ydim; ++j){
077 if (inRun){
078 if (inValues[i][j] == backgroundValue ){
079 inRun = false;
080 }
081 else if (inValues[i][j] != prevValue){
082 prevValue = inValues[i][j];
083 ++N;
084 nIndex.set(N);
085 pixelx.set(nIndex,i);
086 pixely.set(nIndex,j);
087 pixelcount.set(nIndex,1);
088 values.set(nIndex,prevValue);
089 } else {
090 pixelcount.set(nIndex, pixelcount.get(nIndex) + 1);
091 }
092 } else if (inValues[i][j] != backgroundValue){
093 prevValue = inValues[i][j];
094 ++N;
095 nIndex.set(N);
096 pixelx.set(nIndex,i);
097 pixely.set(nIndex,j);
098 pixelcount.set(nIndex,1);
099 values.set(nIndex,prevValue);
100 inRun = true;
101 }
102 }
103 }
104 }
105
106 public ArrayInt getPixelcount() {
107 return pixelcount;
108 }
109
110 public ArrayShort getPixelx() {
111 return pixelx;
112 }
113
114 public ArrayShort getPixely() {
115 return pixely;
116 }
117
118 public ArrayFloat getValues() {
119 return values;
120 }
121
122
123 public static float computeSparseGridRatio(float[][] inValues, float backgroundValue){
124 int xdim = inValues.length;
125 int ydim = inValues[0].length;
126 // find the number of runs in sparse array
127 int N = 0;
128 boolean inRun = false;
129 float prevValue = backgroundValue;
130 for (int i=0; i < xdim; ++i){
131 for (int j=0; j < ydim; ++j){
132 if (inRun){
133 if (inValues[i][j] == backgroundValue ){
134 inRun = false;
135 }
136 else if (inValues[i][j] != prevValue){
137 prevValue = inValues[i][j];
138 ++N;
139 }
140 } else if (inValues[i][j] != backgroundValue){
141 prevValue = inValues[i][j];
142 ++N;
143 inRun = true;
144 }
145 }
146 }
147 float origSize = xdim*ydim;
148 float newSize = N * 4;
149 return (newSize / origSize);
150 }
151 }