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 :
- TinyDB
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,
- When app is not restarted after putObject
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 ]
- When app is restarted and putObject is not called
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.
CodePudding user response：
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