C++ last bit of an image Post: 302510270

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Top Forums Programming C++ last bit of an image Post 302510270 by lamachejo on Saturday 2nd of April 2011 02:47:21 PM

04-02-2011

Registered User

C++ last bit of an image

Hi guys, I've been trying to find out what's wrong with the code, g++ doesn't prompt any error but it doesn't do what I want it to do, and after looking at it over and over I can't find anything wrong with it. The code its quite simple:

I need to save the last bit of every position on the vector and to form a word, for example:
buffer[0] has 00110011
buffer[1] has 11000010

I need to get the last bit and form a letter every 8 bits to decode the sentence.

buffer is a dinamic vector that has the image info loaded on it, cadena is where I want to store the "decoded " letters

Code:

 void revelarPGM (char* &cadena,unsigned char buffer[]) { 
 int binario=0;			
 int j=0;	
 cadena=new char[50000];
 for (int i=0; i<262144; i++) {
     if((buffer[i]&1)==0){ // HERE i use the AND operator to get the last bit, if it is
           binario=(binario<<1);  // A 0, i just shift once
     }else{   
	   binario=(binario<<1);  //IF it is a 1, i shift and add a 1 with the OR
  	   binario=(binario|1);    
     }
   if (i%7==0) {               // WHEN i get 8 bits i store the letter in cadena
          cadena[j]=binario;
          j++;
	  cout << binario << endl;
          binario=0;
  }
 }
 for (int i=0; i<300; i++)
cout << cadena[i];  // cout to see the words i stored.
delete [] cadena;
}

I hope I made myself clear. The problem is I am getting rubbish. But everytime i look at the code, it seems alright to me.

edit: tried to edit the title since i forgot to add it was C++ but it wont allow me now.

Last edited by lamachejo; 04-02-2011 at 03:52 PM..

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sdl_stretchrow1

SDL_SETROWSTRETCHCOD(3) 					   Manual Pages 					   SDL_SETROWSTRETCHCOD(3)

NAME

       SDL_SetRowStretchCode, SDL_PutRowStretchCode, SDL_RunRowStretchCode, SDL_StretchRow1, SDL_StretchRow2, SDL_StretchRow3, SDL_StretchRow4 -
       (src/SDL_stretchcode.h)

SYNOPSIS

	#include <SDL_stretch.h>

       unsigned char* SDL_SetRowStretchCode(int src_w, int dst_w, int bpp);

       unsigned char* SDL_PutRowStretchCode(unsigned char* buffer, int buflen, int src_w, int dst_w, int bpp);

       void SDL_RunRowStretchCode(unsigned char* buffer, unsigned char* src, unsigned char* dst);

       void SDL_StretchRow1(Uint8 *src, int src_w, Uint8 *dst, int dst_w);

       void SDL_StretchRow2(Uint16 *src, int src_w, Uint16 *dst, int dst_w);

       void SDL_StretchRow3(Uint8 *src, int src_w, Uint8 *dst, int dst_w);

       void SDL_StretchRow4(Uint32 *src, int src_w, Uint32 *dst, int dst_w);

DESCRIPTION

       The SetRowStretchCode is a wrapper around PutRowStretchCode that uses the Adress and Size of the shared SDL_TheRowStretchCode buffer. The
       PutRowStretchCode will fill the given buffer with an assembler stream that should be called with SDL_RunRowStretchCode. The assembler
       stream is usually faster as all the scale decisions are done in advance of the execution. This helps when a RunCode is done multiple times
       with the same src_w/dst_w/bpp pair. All the pixel-get and pixel-set calls are unrolled in that buffer. Therefore, the buffer should be big
       enough - as a rule of thumb use a buffer of size (src_w+dst_w)*5

       If PutCode or SetCode fails, a NULL is returned and SDL_SetError. Otherwise, the start adress of the machine code buffer is returned, which
       is also the input argument of PutCode and RunCode.

       If SDL_SetRowStretchCode fails, the SDL_StretchRow1 function must be used instead.  The SDL_StretchRow1 function and its cousins are
       singular routines that work in a tight loop to scale a single row. The number specifies the byte-width of each pixel (it is not a
       bit-width!).

SDL_stretch							       0.3.1						   SDL_SETROWSTRETCHCOD(3)