diff --git a/envi/bil.h b/envi/bil.h
index 47ad258..16edb2c 100644
--- a/envi/bil.h
+++ b/envi/bil.h
@@ -164,13 +164,25 @@ public:
 		file.seekg((y * R[0] * R[2] + x) * sizeof(T), std::ios::beg);
 
 		for(unsigned i = 0; i < R[2]; i++)
-		{         //point to the certain sample and line		
+		{       
+			//point to the certain sample and line		
 			file.read((char *)(p + i), sizeof(T));
 			file.seekg(jump, std::ios::cur);  
 		}	
 
 		return true;	
 	}
+
+	//save one pixel into memory
+	bool pixel(T * p, unsigned n){
+
+		//calculate the corresponding x, y
+		unsigned int x = n % R[0];
+		unsigned int y = n / R[0];
+
+		//get the pixel
+		return spectrum(p, x, y);
+	}
 	
 	//given a Y ,return a XZ slice
 	bool getY(T * p, unsigned y)
diff --git a/envi/bip.h b/envi/bip.h
index f929e20..c1e9b61 100644
--- a/envi/bip.h
+++ b/envi/bip.h
@@ -261,6 +261,20 @@ public:
 			
 		return true;	
 	}
+
+	//save one pixel into memory
+	bool pixel(T * p, unsigned n){
+
+		unsigned bandnum = R[0] * R[1];		//calculate numbers in one band
+		if ( n >= bandnum){							//make sure the pixel number is right
+			std::cout<<"ERROR: sample or line out of range"<<std::endl;
+			return false;
+		}
+
+		file.seekg(n * R[2] * sizeof(T), std::ios::beg);           //point to the certain pixel
+		file.read((char *)p, sizeof(T) * R[2]);
+		return true;	
+	}
 	
 	//given a Y ,return a ZX slice
 	bool getY(T * p, unsigned y)
diff --git a/envi/bsq.h b/envi/bsq.h
index 095b0f2..d8d7b13 100644
--- a/envi/bsq.h
+++ b/envi/bsq.h
@@ -118,7 +118,7 @@ public:
 		}
 
 		file.seekg((x + y * R[0]) * sizeof(T), std::ios::beg);           //point to the certain sample and line
-		for (i = 0; i < R[3]; i++)
+		for (i = 0; i < R[2]; i++)
 		{
 			file.read((char *)(p + i), sizeof(T));
 			file.seekg((R[1] * R[0] - 1) * sizeof(T), std::ios::cur);    //go to the next band
@@ -127,6 +127,25 @@ public:
 		return true;	
 	}
 
+	//save one pixel into memory
+	bool pixel(T * p, unsigned n){
+
+		unsigned bandnum = R[0] * R[1];		//calculate numbers in one band
+		if ( n >= bandnum){							//make sure the pixel number is right
+			std::cout<<"ERROR: sample or line out of range"<<std::endl;
+			return false;
+		}
+
+		file.seekg(n * sizeof(T), std::ios::beg);           //point to the certain pixel
+		for (unsigned i = 0; i < R[2]; i++)
+		{
+			file.read((char *)(p + i), sizeof(T));
+			file.seekg((bandnum - 1) * sizeof(T), std::ios::cur);    //go to the next band
+		}
+
+		return true;	
+	}
+
 	//baseline correction and save it into file
 	
 	bool baseline(std::string outname, std::vector<double> wls )
diff --git a/envi/envi.h b/envi/envi.h
index 8dc7977..8d1eb07 100644
--- a/envi/envi.h
+++ b/envi/envi.h
@@ -5,6 +5,8 @@
 #include "../envi/bsq.h"
 #include "../envi/bip.h"
 #include "../envi/bil.h"
+#include <iostream>
+#include "../../CImg/CImg.h"
 
 namespace stim{
 
@@ -524,6 +526,40 @@ public:
 		}
 		return false;
 	}
+	//get one pixel from binary file
+	bool pixel(void * p, unsigned n){
+		if(header.interleave == envi_header::BSQ){
+			if(header.data_type ==envi_header::float32)
+				return ((bsq<float>*)file)->pixel((float*)p, n);
+			else if(header.data_type == envi_header::float64)
+				return ((bsq<double>*)file)->pixel((double*)p, n);
+			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)->pixel((float*)p, n);
+			else if(header.data_type == envi_header::float64)
+				return ((bil<double>*)file)->pixel((double*)p, n);
+			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)->pixel((float*)p, n);
+			else if(header.data_type == envi_header::float64)
+				return ((bip<double>*)file)->pixel((double*)p, n);
+			else{
+				std::cout<<"ERROR: unidentified data type"<<std::endl;
+				exit(1);
+			}
+		}
+		return false;
+	}
 
 	bool save_header(std::string filename){
 
@@ -551,8 +587,54 @@ public:
 		}
 		return false;
 	}
+	/*
+	//load mask from maskfile and save it into memory
+	bool load_mask(unsigned char * mask, std::string maskname){
+		//open the mask file
+		cimg_library::CImg<unsigned char> mask_image(maskname.c_str(),true);
+		//save mask file into memory
+		for (unsigned i = 0; i < header.lines * header.samples; i++)
+				mask[i] = mask_image.at(i);		//how to copy value from cimg class?
+		//close mask file
+		mask_image.clear();
+		return true;
+	}*/
 
-
+	//p:start positon; N: number of pixels saved in X;
+	bool feature_matrix(void * X, std::string maskname, unsigned char * mask, unsigned start, unsigned N)
+	{
+		cimg_library::CImg<unsigned char> mask_image(maskname.c_str());
+		//save mask file into memory
+		mask = mask_image.data();
+		//save pixels in X as floating numbers
+		float * p = (float *)malloc(header.bands * sizeof(float));
+		
+		//use mask to save valid pixel in X
+		unsigned bandnum = header.samples * header.lines;		//calculate pixel numbers in a band
+		unsigned count = 0;		//for counting use
+		unsigned j = 0;		//memory the pointer location in X
+
+		for(unsigned i = start; i < bandnum; i++){
+			if(mask[i] != 0){
+				pixel(p, i);
+				//copy p to X
+				for(unsigned k = 0; k < header.bands; k++){
+					((float *)X)[j] = p[k];
+					j++;
+				}
+				count++;
+				if(count == N)
+					break;
+			}
+			else
+				continue;
+		}
+		if(count < N){
+			std::cout << "number of valid pixels in the mask : " << count <<"is less than N: "<< N;
+			exit(1);
+		}
+		return true;
+	}
 
 
 
--
libgit2 0.21.4