java - Text extraction and segmentation open CV -

i've never used opencv before, i'm trying write neural network system recognize text , need tool text extraction/ segmentation.

how can use java opencv preprocess , segmentate image containing text.
i don't need recognize text, need each letter in separate image.
something :

try code .no need of opencv

import java.awt.image.bufferedimage; import java.util.arraylist; import java.util.list; import org.neuroph.imgrec.imageutilities;   public class charextractor {  private int croptopy = 0;//up locked coordinate private int cropbottomy = 0;//down locked coordinate private int cropleftx = 0;//left locked coordinate private int croprightx = 0;//right locked coordinate private bufferedimage imagewithchars = null; private boolean endofimage;//end of picture private boolean endofrow;//end of current reading row  /**  * creates new char extractor soecified text image  * @param imagewithchars - image text  */ public charextractor(bufferedimage imagewithchars) {     this.imagewithchars = imagewithchars; }  public void setimagewithchars(bufferedimage imagewithchars) {     this.imagewithchars = imagewithchars; }  /**  * method scans image pixels until finds first black pixel (todo: use         foreground color black default).  * when finds black pixel, sets croptopy , returns true. if reaches end of image , not find black pixels,   * sets endofimage flag , returns false.  * @return - returns true when black pixel found , croptopy value changed, , false if croptopy value not changed  */  private boolean findcroptopy() {     (int y = cropbottomy; y < imagewithchars.getheight(); y++) { // why cropydown? -   multiple lines of text using cropbottomy previous line above; first line 0         (int x = cropleftx; x < imagewithchars.getwidth(); x++) { // scan starting previous left crop position - or shoud right???             if (imagewithchars.getrgb(x, y) == -16777216) { // if black rixel (also consider condition close black or not white or different background)                 this.croptopy = y;   // save current y coordiante                 return true;        // , return true             }         }     }     endofimage = true;  //sets flag if no black pixels found     return false;       // , return false }  /**  * method scans image pixels until finds first row white pixels. (todo: background color white default).  * when finds line whith white pixels, sets cropbottomy , returns true  * @return - returns true when cropbottomy value set, false otherwise  */ private boolean findcropbottomy() {     (int y = croptopy + 1; y < imagewithchars.getheight(); y++) { // scan image  top bottom                    int whitepixcounter = 0; //counter of white pixels in row         (int x = cropleftx; x < imagewithchars.getwidth(); x++) { // scan pixels right starting left crop position             if (imagewithchars.getrgb(x, y) == -1) {    // if white pixel                 whitepixcounter++;                      // increase counter             }         }         if (whitepixcounter == imagewithchars.getwidth()-1) { // if have reached end of line counting white pixels (x pos)             cropbottomy = y;// means we've found white line, set current y coordinate minus 1             return true; // cropbottomy , finnish true         }         if (y == imagewithchars.getheight() - 1) {  // if have reached end of image              cropbottomy = y;                        // set crop bottom             endofimage = true;                      // set corresponding endofimage flag             return true;                            // , return true         }     }     return false;                                   // should never happen, possible if image has non white bg }  private boolean findcropleftx() {             int whitepixcounter = 0;                                            // white pixel counter between letters     (int x = croprightx; x < imagewithchars.getwidth(); x++) {      // start previous righ crop position (previous letter), , scan following pixels right         (int y = croptopy; y <= cropbottomy; y++) {             // vertical pixel scan @ current x coordinate             if (imagewithchars.getrgb(x, y) == -16777216) {             // when find black pixel                 cropleftx = x;                                          // set cropleftx                 return true;                                            // , return true             }         }          // bug?: condition looks strange.... might not need whitepixcounter @ all, might used 'i' letter         whitepixcounter++;                                              // if not black pixel assume white pixel         if (whitepixcounter == 3) {                                     // why 3 pixels? hard coded case , not work in general...!!!             whitepixcounter = 0;                                        // why sets zero, has no purporse @ all...         }     }     endofrow = true;        // if have reached end of row , have not found black pixels, set endofrow flag     return false;           // , return false }  /**  * method scans image pixels right until finds next row pixel white, y1 , y2.  * @return - return true  when x2 value changed , false when x2 value not changed  */ private boolean findcroprightx() {     (int x = cropleftx + 1; x < imagewithchars.getwidth(); x++) {   // start current cropleftx position , scan pixels right         int whitepixcounter = 0;         (int y = croptopy; y <= cropbottomy; y++) {             // vertical pixel scan @ current x coordinate             if (imagewithchars.getrgb(x, y) == -1) {                    // if have white pixel @ current (x, y)                 whitepixcounter++;                                      // increase whitepixcounter             }         }          // space!         int heightpixels = cropbottomy - croptopy;                      // calculate crop height         if (whitepixcounter == heightpixels+1) {                         // if white pixel count equal crop height+1  white vertical line, means end of current char/ (+1 case when there 1 pixel; 'w' bug fix)             croprightx = x;                                             // set croprightx                 return true;                                                // , return true         }          // why need when allready have condiiton in loop? - last letter in row.         if (x == imagewithchars.getwidth() - 1) {                       // if have reached end of row x position                 croprightx = x;                                             // set croprightx             endofrow = true;                                            // set endofrow flag             return true;                                                // , return true         }     }        }  public list<bufferedimage> extractcharimagestorecognize() {     list<bufferedimage> trimedimages = new arraylist<bufferedimage>();     int = 0;      while (endofimage == false) {         endofrow = false;         boolean foundtop = findcroptopy();         boolean foundbottom = false;         if (foundtop == true) {             foundbottom = findcropbottomy();             if (foundbottom == true) {                 while (endofrow == false) {                     boolean foundleft = false;                     boolean foundright = false;                     foundleft = findcropleftx();                     if (foundleft == true) {                         foundright = findcroprightx();                         if (foundright == true) {                             bufferedimage image = imageutilities.trimimage(imageutilities.cropimage(imagewithchars, cropleftx, croptopy, croprightx, cropbottomy));                             trimedimages.add(image);                                                             i++;                                                                                                        }                     }                 }                 cropleftx = 0;                 croprightx = 0;             }         }     }     croptopy = 0;     cropbottomy = 0;     endofimage = false;      return trimedimages; }   public static void main(string[] args) throws exception {     file f=new file("./written.png");     bufferedimage img=imageio.read(f);     charextractor ch=new charextractor(img);     list<bufferedimage> list=ch.extractcharimagestorecognize();      for(int i=0;i<list.size();i++)     {          file outputfile = new file("./char_" +i+ ".png");          imageio.write(list.get(i),"png", outputfile);     }         } }