diff --git a/envi/bil.h b/envi/bil.h
index 16edb2c..f9007fc 100644
--- a/envi/bil.h
+++ b/envi/bil.h
@@ -727,6 +727,130 @@ public:
 		return true;
 	}
 
+	//calculate the average band value
+	bool band_avg(T* p){
+		unsigned long long XZ = R[0] * R[2];
+		T* temp = (T*)malloc(sizeof(T) * XZ);
+		T* line = (T*)malloc(sizeof(T) * R[0]);
+
+		for (unsigned i = 0; i < R[1]; i++){
+			getY(temp, i);
+			//initialize x-line
+			for (unsigned j = 0; j < R[0]; j++){
+				line[j] = 0;
+			}
+			unsigned c = 0;
+			for (unsigned j = 0; j < R[2]; j++){
+				for (unsigned k = 0; k < R[0]; k++){
+					line[k] += temp[c] / (T)R[2];
+					c++;
+				}
+			}
+			for (unsigned j = 0; j < R[0]; j++){
+				p[j + i * R[0]] = line[j];
+			}
+		}
+		free(temp);
+		return true;
+	}
+
+	//calculate the average number of every band
+	bool avg_band(T*p, unsigned char* mask){
+		unsigned long long XZ = R[0] * R[2];
+		unsigned long long XY = R[0] * R[1];
+		T* temp = (T*)malloc(sizeof(T) * XZ);
+		for (unsigned j = 0; j < R[2]; j++){
+			p[j] = 0;
+		}
+		//calculate vaild number in a band
+		unsigned count = 0;
+		for (unsigned j = 0; j < XY; j++){
+			if (mask[j] != 0){
+				count++;
+			}
+		}
+		for (unsigned k = 0; k < R[1]; k++){
+			getY(temp, k);
+			unsigned kx = k * R[0];
+			for (unsigned i = 0; i < R[0]; i++){
+				if (mask[kx + i] != 0){
+					for (unsigned j = 0; j < R[2]; j++){
+						p[j] += temp[j * R[0] + i] / (T)count;
+					}
+				}
+			}
+		}
+		free(temp);
+		return true;
+	}
+
+	//calculate correlation coefficient matrix
+	bool co_matrix(T* co, T* avg, unsigned char *mask){
+		//memory allocation
+		unsigned long long xy = R[0] * R[1];
+		unsigned int B = R[2];
+		T* temp = (T*)malloc(sizeof(T) * B);
+		//count vaild pixels in a band
+		unsigned count = 0;
+		for (unsigned j = 0; j < xy; j++){
+			if (mask[j] != 0){
+				count++;
+			}
+		}
+		//initialize correlation matrix
+		for (unsigned i = 0; i < B; i++){
+			for (unsigned k = 0; k < B; k++){
+				co[i * B + k] = 0;
+			}
+		}
+		//calculate correlation coefficient matrix
+		for (unsigned j = 0; j < xy; j++){
+			if (mask[j] != 0){
+				pixel(temp, j);
+				for (unsigned i = 0; i < B; i++){
+					for (unsigned k = i; k < B; k++){
+						co[i * B + k] += (temp[i] - avg[i]) * (temp[k] - avg[k]) / count;
+					}
+				}
+			}
+		}
+		//because correlation matrix is symmetric
+		for (unsigned i = 0; i < B; i++){
+			for (unsigned k = i + 1; k < B; k++){
+				co[k * B + i] = co[i * B + k];
+			}
+		}
+
+		free(temp);
+		return true;
+	}
+
+	//crop specified area the of the original file
+	bool crop(std::string outfile, unsigned x0, unsigned y0, unsigned x1, unsigned y1){
+
+		//calculate the new number of samples and lines
+		unsigned long long sam = x1 - x0;		//samples
+		unsigned long long lin = y1 - y0;		//lines
+		unsigned long long L = sam * R[2] * sizeof(T);
+		//get specified band and save
+		T* temp = (T*)malloc(L);
+		std::ofstream out(outfile.c_str(), std::ios::binary);
+		unsigned long long jumpb = (R[0] - sam) * sizeof(T);		//jump pointer to the next band
+		//get start
+		file.seekg((y0 * R[0] * R[2] + x0) * sizeof(T), std::ios::beg);
+		for (unsigned i = 0; i < lin; i++)
+		{
+			for (unsigned j = 0; j < R[2]; j++)
+			{
+				file.read((char *)(temp + j * sam), sizeof(T) * sam);
+				file.seekg(jumpb, std::ios::cur);    //go to the next band	
+			}
+			out.write(reinterpret_cast<const char*>(temp), L);   //write slice data into target file	
+		}
+		free(temp);
+		return true;
+	}
+
 	//close the file
 	bool close(){
 		file.close();
diff --git a/envi/bip.h b/envi/bip.h
index c1e9b61..87eb151 100644
--- a/envi/bip.h
+++ b/envi/bip.h
@@ -821,6 +821,117 @@ public:
 		return true;
 	}
 
+	//calculate the average band of the file
+	bool band_avg(T* p){
+		unsigned long long XY = R[0] * R[1];
+		//get every pixel and calculate average value
+		T* temp = (T*)malloc(sizeof(T) * R[2]);
+		T sum;
+		for (unsigned i = 0; i < XY; i++){
+			pixel(temp, i);
+			//calculate the sum value of every value
+			sum = 0;		//initialize sum value
+			for (unsigned j = 0; j < R[2]; j++){
+				sum += temp[j]/(T)R[2];
+			}
+			p[i] = sum;
+		}
+		free(temp);
+		return true;
+	}
+
+	//calculate the average number of every band
+	bool avg_band(T*p, unsigned char* mask){
+		unsigned long long XY = R[0] * R[1];
+		T* temp = (T*)malloc(sizeof(T) * R[2]);
+		//Iinitialize
+		for (unsigned j = 0; j < R[2]; j++){
+			p[j] = 0;
+		}
+		//calculate vaild number in a band
+		unsigned count = 0;
+		for (unsigned j = 0; j < XY; j++){
+			if (mask[j] != 0){
+				count++;
+			}
+		}
+		//calculate average number of a band
+		for (unsigned i = 0; i < XY; i++){
+			if (mask[i] != 0){			
+				pixel(temp, i);
+				for (unsigned j = 0; j < R[2]; j++){
+					p[j] += temp[j] / (T)count;
+				}
+			}
+		}
+		free(temp);
+		return true;
+	}
+	//calculate correlation coefficient matrix
+	bool co_matrix(T* co, T* avg, unsigned char *mask){
+		//memory allocation
+		unsigned long long xy = R[0] * R[1];
+		unsigned int B = R[2];
+		T* temp = (T*)malloc(sizeof(T) * B);
+		//count vaild pixels in a band
+		unsigned count = 0;
+		for (unsigned j = 0; j < xy; j++){
+			if (mask[j] != 0){
+				count++;
+			}
+		}
+		//initialize correlation matrix
+		for (unsigned i = 0; i < B; i++){
+			for (unsigned k = 0; k < B; k++){
+				co[i * B + k] = 0;
+			}
+		}
+		//calculate correlation coefficient matrix
+		for (unsigned j = 0; j < xy; j++){
+			if (mask[j] != 0){
+				pixel(temp, j);
+				for (unsigned i = 0; i < B; i++){
+					for (unsigned k = i; k < B; k++){
+						co[i * B + k] += (temp[i] - avg[i]) * (temp[k] - avg[k]) / count;
+					}
+				}
+			}
+		}
+		//because correlation matrix is symmetric
+		for (unsigned i = 0; i < B; i++){
+			for (unsigned k = i + 1; k < B; k++){
+				co[k * B + i] = co[i * B + k];
+			}
+		}
+
+		free(temp);
+		return true;
+	}
+
+	//crop specified area the of the original file
+	bool crop(std::string outfile, unsigned x0, unsigned y0, unsigned x1, unsigned y1){
+
+		//calculate the new number of samples and lines
+		unsigned long long sam = x1 - x0;		//samples
+		unsigned long long lin = y1 - y0;		//lines
+		unsigned long long L = R[2] * sizeof(T);
+		//get specified band and save
+		T* temp = (T*)malloc(L);
+		std::ofstream out(outfile.c_str(), std::ios::binary);
+		//get start
+		unsigned long long sp = y0 * R[0] + x0;		//start pixel
+		for (unsigned i = 0; i < lin; i++)
+		{
+			for (unsigned j = 0; j < sam; j++)
+			{
+				pixel(temp, sp + j + i * R[0]);
+				out.write(reinterpret_cast<const char*>(temp), L);   //write slice data into target file	
+			}
+		}
+		free(temp);
+		return true;
+	}
+
 	//close the file
 	bool close(){
 		file.close();
diff --git a/envi/bsq.h b/envi/bsq.h
index 099df79..ba6e4dd 100644
--- a/envi/bsq.h
+++ b/envi/bsq.h
@@ -663,6 +663,115 @@ public:
 		return true;
 	}
 
+	//calculate the average band
+	bool band_avg(T* p){
+		unsigned long long XY = R[0] * R[1];
+		T* temp = (T*)malloc(sizeof(T) * XY);
+		//initialize p
+		band_index(p, 0);
+		for (unsigned j = 0; j < XY; j++){
+			p[j] /= (T)R[2];
+		}
+		//get every band and add them all
+		for (unsigned i = 1; i < R[2]; i++){
+			band_index(temp, i);
+			for (unsigned j = 0; j < XY; j++){
+				p[j] += temp[j]/(T)R[2];
+			}
+		}
+		free(temp);
+		return true;
+	}
+
+	//calculate the average number of every band
+	bool avg_band(T*p, unsigned char* mask){
+		unsigned long long XY = R[0] * R[1];
+		unsigned count = 0;		//number of vaild pixel in a band
+		T* temp = (T*)malloc(sizeof(T) * XY);
+		//calculate valid pixel number
+		for (unsigned j = 0; j < XY; j++){
+			if (mask[j] != 0){
+				count++;
+			}
+		}
+		//calculate average of a band
+		for (unsigned i = 0; i < R[2]; i++){
+			p[i] = 0;
+			band_index(temp, i);
+			for (unsigned j = 0; j < XY; j++){
+				if (mask[j] != 0){
+					p[i] += temp[j] / (T)count;
+				}				
+			}
+		}
+		free(temp);
+		return true;
+	}
+
+	//calculate correlated matrix
+	bool co_matrix(T* co, T* avg, unsigned char *mask){
+		//memory allocation
+		unsigned long long xy = R[0] * R[1];
+		unsigned int B = R[2];
+		T* bandi = (T*)malloc(sizeof(T) * xy);
+		T* bandj = (T*)malloc(sizeof(T) * xy);
+		
+		//count vaild pixels in a band
+		unsigned count = 0;
+		for (unsigned j = 0; j < xy; j++){
+			if (mask[j] != 0){
+				count++;
+			}
+		}
+		//calculate correlation coefficient matrix
+		for (unsigned i = 0; i < B; i++)
+		{
+			band_index(bandi, i);
+			for (unsigned j = i; j < B; j++){
+				band_index(bandj, j);
+				T numerator = 0;			//to calculate element in correlation coefficient matrix, numerator part
+				//calculate the R(i,j) in correlation coeffient matrix
+				for (unsigned k = 0; k < xy; k++){
+					if (mask[k] != 0){
+						numerator += (bandi[k] - avg[i]) * (bandj[k] - avg[j]) / count;
+					}
+				}
+				co[i*B + j] = numerator;
+				co[j*B + i] = numerator;		//because correlated matrix is a symmetric matrix
+			}
+		}
+		free(bandi);
+		free(bandj);
+		return true;
+	}
+
+	//crop specified area the of the original file
+	bool crop(std::string outfile, unsigned x0, unsigned y0, unsigned x1, unsigned y1){
+
+		//calculate the new number of samples and lines
+		unsigned long long sam = x1 - x0;		//samples
+		unsigned long long lin = y1 - y0;		//lines
+		unsigned long long L = sam * lin * sizeof(T);
+		//get specified band and save
+		T* temp = (T*)malloc(L);
+		std::ofstream out(outfile.c_str(), std::ios::binary);
+		unsigned long long jumpb = R[0] * (R[1] - lin) * sizeof(T);		//jump pointer to the next band
+		unsigned long long jumpl = (R[0] - sam) * sizeof(T);	                           	//jump pointer to the next line
+		//get start
+		file.seekg((y0 * R[0] + x0) * sizeof(T), std::ios::beg);
+		for (unsigned i = 0; i < R[2]; i++)
+		{
+			for (unsigned j = 0; j < lin; j++)
+			{
+				file.read((char *)(temp + j * sam), sizeof(T) * sam);
+				file.seekg(jumpl, std::ios::cur);    //go to the next band	
+			}
+			out.write(reinterpret_cast<const char*>(temp), L);   //write slice data into target file	
+			file.seekg(jumpb, std::ios::cur);
+		}
+		free(temp);
+		return true;
+	}
 
 	//close the file
 	bool close(){
diff --git a/envi/envi.h b/envi/envi.h
index b2e2e4b..040883e 100644
--- a/envi/envi.h
+++ b/envi/envi.h
@@ -642,8 +642,111 @@ public:
 		return true;
 	}
 
+	//calculate band average
+	bool avg_band(void * p, unsigned char* mask){
+		if (header.interleave == envi_header::BSQ){
+			if (header.data_type == envi_header::float32)
+				return ((bsq<float>*)file)->avg_band((float*)p, mask);
+			else if (header.data_type == envi_header::float64)
+				return ((bsq<double>*)file)->avg_band((double*)p,  mask);
+			else{
+				std::cout << "ERROR: unidentified data type" << std::endl;
+				exit(1);
+			}
+		}
+		else if (header.interleave == envi_header::BIL){
+			if (header.data_type == envi_header::float32)
+				return ((bil<float>*)file)->avg_band((float*)p,  mask);
+			else if (header.data_type == envi_header::float64)
+				return ((bil<double>*)file)->avg_band((double*)p,  mask);
+			else{
+				std::cout << "ERROR: unidentified data type" << std::endl;
+				exit(1);
+			}
+		}
+		else if (header.interleave == envi_header::BIP){
+			if (header.data_type == envi_header::float32)
+				return ((bip<float>*)file)->avg_band((float*)p, mask);
+			else if (header.data_type == envi_header::float64)
+				return ((bip<double>*)file)->avg_band((double*)p, mask);
+			else{
+				std::cout << "ERROR: unidentified data type" << std::endl;
+				exit(1);
+			}
+		}
+		return false;
+	}
 
+	//calculate correlation coefficient matrix with mask
+	bool co_matrix(void* co, void* avg, unsigned char* mask){
+		if (header.interleave == envi_header::BSQ){
+			if (header.data_type == envi_header::float32)
+				return ((bsq<float>*)file)->co_matrix((float*)co, (float*)avg, mask);
+			else if (header.data_type == envi_header::float64)
+				return ((bsq<double>*)file)->co_matrix((double*)co, (double*)avg, mask);
+			else{
+				std::cout << "ERROR: unidentified data type" << std::endl;
+				exit(1);
+			}
+		}
+		else if (header.interleave == envi_header::BIL){
+			if (header.data_type == envi_header::float32)
+				return ((bil<float>*)file)->co_matrix((float*)co, (float*)avg, mask);
+			else if (header.data_type == envi_header::float64)
+				return ((bil<double>*)file)->co_matrix((double*)co, (double*)avg, mask);
+			else{
+				std::cout << "ERROR: unidentified data type" << std::endl;
+				exit(1);
+			}
+		}
+		else if (header.interleave == envi_header::BIP){
+			if (header.data_type == envi_header::float32)
+				return ((bip<float>*)file)->co_matrix((float*)co, (float*)avg, mask);
+			else if (header.data_type == envi_header::float64)
+				return ((bip<double>*)file)->co_matrix((double*)co, (double*)avg, mask);
+			else{
+				std::cout << "ERROR: unidentified data type" << std::endl;
+				exit(1);
+			}
+		}
+		return false;
+	}
 
+	//crop specified area the of the original file
+	bool crop(std::string outfile,unsigned x0, unsigned y0, unsigned x1, unsigned y1){
+
+		if (header.interleave == envi_header::BSQ){
+			if (header.data_type == envi_header::float32)
+				return ((bsq<float>*)file)->crop(outfile, x0, y0, x1, y1);
+			else if (header.data_type == envi_header::float64)
+				return ((bsq<double>*)file)->crop(outfile, x0, y0, x1, y1);
+			else{
+				std::cout << "ERROR: unidentified data type" << std::endl;
+				exit(1);
+			}
+		}
+		else if (header.interleave == envi_header::BIL){
+			if (header.data_type == envi_header::float32)
+				return ((bil<float>*)file)->crop(outfile, x0, y0, x1, y1);
+			else if (header.data_type == envi_header::float64)
+				return ((bil<double>*)file)->crop(outfile, x0, y0, x1, y1);
+			else{
+				std::cout << "ERROR: unidentified data type" << std::endl;
+				exit(1);
+			}
+		}
+		else if (header.interleave == envi_header::BIP){
+			if (header.data_type == envi_header::float32)
+				return ((bip<float>*)file)->crop(outfile, x0, y0, x1, y1);
+			else if (header.data_type == envi_header::float64)
+				return ((bip<double>*)file)->crop(outfile, x0, y0, x1, y1);
+			else{
+				std::cout << "ERROR: unidentified data type" << std::endl;
+				exit(1);
+			}
+		}
+		return false;
+	}
 };
 
 }	//end namespace rts
--
libgit2 0.21.4