I am using SIFT by opencv in android studio JAVA language. I want to save the features of the image which are Mat and MatOfKeyPoint so that next for the same image I don't have to recalculate those features.
So far I have tried :
ISSUE : It gets the data corrupted when app is restarted. Below is the code I used to save for Mat, same I have applied for MatOfKeyPoint too
tinyDB.putObject("MAT_DATA", (Object) mat_descriptors);
for reading I am using this
Log.d("TINYDB_", "MAT : "+tinyDB.getObject("MAT_DATA", Mat.class)+"");
below are logs while I am reading object,
2022-08-15 11:15:35.166 5143-5143/com.programminghut.opencv D/TINYDB_: MAT : Mat [ 59868*128*CV_32FC1, isCont=true, isSubmat=false, nativeObj=0xb4000071f399bcb0, dataAddr=0xb4000070f2d8e000 ]
2022-08-15 11:16:09.405 5268-5268/com.programminghut.opencv D/TINYDB_: MAT : Mat [ -1*-1*CV_8UC1, isCont=true, isSubmat=false, nativeObj=0xb4000071f399bcb0, dataAddr=0x0 ]
Now I am looking either solution to the above tinyDB problem or If you think anything else could utilised to save Mat into local storage that would also be very helpful.
Thanks to @sorifiend I was able to store Mat via tinyDB.
how-to-serialize-deserialize-opencv-mat-in-java :- It works for only for Mat
I did more googling and found a solution on stack overflow for MatOfKeyPoint too but can not find link to it.
So below is the class I made after combining both the solutions :
import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import org.opencv.core.KeyPoint;
import org.opencv.core.Mat;
import org.opencv.core.MatOfKeyPoint;
import org.opencv.core.Point;
class SerializeTheMat
{
public static String keypointsToJson(MatOfKeyPoint mat){
if(mat!=null && !mat.empty()){
Gson gson = new Gson();
JsonArray jsonArr = new JsonArray();
KeyPoint[] array = mat.toArray();
for(int i=0; i<array.length; i++){
KeyPoint kp = array[i];
JsonObject obj = new JsonObject();
obj.addProperty("class_id", kp.class_id);
obj.addProperty("x", kp.pt.x);
obj.addProperty("y", kp.pt.y);
obj.addProperty("size", kp.size);
obj.addProperty("angle", kp.angle);
obj.addProperty("octave", kp.octave);
obj.addProperty("response", kp.response);
jsonArr.add(obj);
}
String json = gson.toJson(jsonArr);
return json;
}
return "{}";
}
public static MatOfKeyPoint keypointsFromJson(String json){
MatOfKeyPoint result = new MatOfKeyPoint();
JsonParser parser = new JsonParser();
JsonArray jsonArr = parser.parse(json).getAsJsonArray();
int size = jsonArr.size();
KeyPoint[] kpArray = new KeyPoint[size];
for(int i=0; i<size; i++){
KeyPoint kp = new KeyPoint();
JsonObject obj = (JsonObject) jsonArr.get(i);
Point point = new Point(
obj.get("x").getAsDouble(),
obj.get("y").getAsDouble()
);
kp.pt = point;
kp.class_id = obj.get("class_id").getAsInt();
kp.size = obj.get("size").getAsFloat();
kp.angle = obj.get("angle").getAsFloat();
kp.octave = obj.get("octave").getAsInt();
kp.response = obj.get("response").getAsFloat();
kpArray[i] = kp;
}
result.fromArray(kpArray);
return result;
}
// Serialization/deserialization utility
public static String SerializeFromMat(Mat mat)
{
SerializedMat serializedMat = new SerializedMat();
serializedMat.setType(mat.type());
serializedMat.setRows(mat.rows());
serializedMat.setCols(mat.cols());
if (serializedMat.getType()==0||
serializedMat.getType()==8||
serializedMat.getType()==16||
serializedMat.getType()==24)
{
serializedMat.setBytes(new byte[(int)(mat.total()*mat.elemSize())]);
mat.get(0,0,serializedMat.bytes);
}
else if (serializedMat.getType()==1||
serializedMat.getType()==9||
serializedMat.getType()==17||
serializedMat.getType()==25)
{
serializedMat.setBytes(new byte[(int)(mat.total()*mat.elemSize())]);
mat.get(0,0,serializedMat.bytes);
}
else if (serializedMat.getType()==2||
serializedMat.getType()==10||
serializedMat.getType()==18||
serializedMat.getType()==26)
{
serializedMat.setShorts(new short[(int)(mat.total()*mat.elemSize())]);
mat.get(0,0,serializedMat.shorts);
}
else if (serializedMat.getType()==3||
serializedMat.getType()==11||
serializedMat.getType()==19||
serializedMat.getType()==27)
{
serializedMat.setShorts(new short[(int)(mat.total()*mat.elemSize())]);
mat.get(0,0,serializedMat.shorts);
}
else if (serializedMat.getType()==4||
serializedMat.getType()==12||
serializedMat.getType()==20||
serializedMat.getType()==28)
{
serializedMat.setInts(new int[(int)(mat.total()*mat.elemSize())]);
mat.get(0,0,serializedMat.ints);
}
else if (serializedMat.getType()==5||
serializedMat.getType()==13||
serializedMat.getType()==21||
serializedMat.getType()==29)
{
serializedMat.setFloats(new float[(int)(mat.total()*mat.elemSize())]);
mat.get(0,0,serializedMat.floats);
}
else if (serializedMat.getType()==6||
serializedMat.getType()==14||
serializedMat.getType()==22||
serializedMat.getType()==30)
{
serializedMat.setDoubles(new double[(int)(mat.total()*mat.elemSize())]);
mat.get(0,0,serializedMat.doubles);
}
// return "";
Gson gson = new Gson();
return gson.toJson(serializedMat);
}
public static Mat DeserializeToMat(String json)
{
Gson gson = new Gson();
SerializedMat serializedMat = gson.fromJson(json, SerializedMat.class);
Mat mat = new Mat(serializedMat.getRows(),serializedMat.getCols(),serializedMat.getType());
if (serializedMat.getType()==0||
serializedMat.getType()==8||
serializedMat.getType()==16||
serializedMat.getType()==24)
{
mat.put(0,0,serializedMat.getBytes());
}
else if (serializedMat.getType()==1||
serializedMat.getType()==9||
serializedMat.getType()==17||
serializedMat.getType()==25)
{
mat.put(0,0,serializedMat.getBytes());
}
else if (serializedMat.getType()==2||
serializedMat.getType()==10||
serializedMat.getType()==18||
serializedMat.getType()==26)
{
mat.put(0,0,serializedMat.getShorts());
}
else if (serializedMat.getType()==3||
serializedMat.getType()==11||
serializedMat.getType()==19||
serializedMat.getType()==27)
{
mat.put(0,0,serializedMat.getShorts());
}
else if (serializedMat.getType()==4||
serializedMat.getType()==12||
serializedMat.getType()==20||
serializedMat.getType()==28)
{
mat.put(0,0,serializedMat.getInts());
}
else if (serializedMat.getType()==5||
serializedMat.getType()==13||
serializedMat.getType()==21||
serializedMat.getType()==29)
{
mat.put(0,0,serializedMat.getFloats());
}
else if (serializedMat.getType()==6||
serializedMat.getType()==14||
serializedMat.getType()==22||
serializedMat.getType()==30)
{
mat.put(0,0,serializedMat.getDoubles());
}
return mat;
}
private static class SerializedMat
{
byte[] bytes;
short[] shorts;
int[] ints;
float[] floats;
double[] doubles;
int type;
int rows;
int cols;
byte[] getBytes()
{
return bytes;
}
void setBytes(byte[] bytes)
{
this.bytes = bytes;
}
short[] getShorts()
{
return shorts;
}
void setShorts(short[] shorts)
{
this.shorts = shorts;
}
int[] getInts()
{
return ints;
}
void setInts(int[] ints)
{
this.ints = ints;
}
float[] getFloats()
{
return floats;
}
void setFloats(float[] floats)
{
this.floats = floats;
}
double[] getDoubles()
{
return doubles;
}
void setDoubles(double[] doubles)
{
this.doubles = doubles;
}
int getType()
{
return type;
}
void setType(int type)
{
this.type = type;
}
int getRows()
{
return rows;
}
void setRows(int rows)
{
this.rows = rows;
}
int getCols()
{
return cols;
}
void setCols(int cols)
{
this.cols = cols;
}
SerializedMat()
{
}
}
}
And you can store using tinyDB like below
String kp_to_json=SerializeTheMat.keypointsToJson(kp_ref);
String descriptors = SerializeTheMat.SerializeFromMat(data);
tinyDB.putString("DESC", descriptors);
tinyDB.putString("KP", kp_to_json);
And get it back like follows:
data = SerializeTheMat.DeserializeToMat(tinyDB.getString("DESC"));
kp_ref = SerializeTheMat.keypointsFromJson(tinyDB.getString("KP"));
For storing them locally you can write JSON file from those string and read those JSON files whenever needed.
THANKS