BMP Reader C Code

Mitesh Karwa

I was developing a simple program to read an 24-bit BMP image, convert it into 8-bit intensity map and then display it as a grayscale image. Please review this code and tell me where I am getting an error...

#include<stdio.h>
#include<conio.h>
#pragma pack(2)

typedef struct
{
unsigned short int type;
unsigned int size;
unsigned short int reserved1,reserved2;
unsigned int offset;
}HEADER;

typedef struct
{
unsigned int size;
int width,height;
unsigned short int bits;
unsigned int compression;
unsigned int imagesize;
int xresolution,yresolution;
unsigned int ncolors;
unsigned int impcolors;
}INFOHEADER;

typedef struct
{
unsigned int R,G,B;
}PIXEL;

void main()
{
HEADER headfirst;
INFOHEADER headsecond;
PIXEL pix;
FILE *fin,*fout,*f1;
char *read;
int ch=0,i,j,mat[768],R[256],G[256],B[256],Gray[256];
float Y[256];

  //Read Image Header
  fin=fopen("C:/Dev-Cpp/1.bmp","rb+");
  if(fin==NULL)
  {
               printf("Error");
               exit(0);
  }
  fread(&headfirst,sizeof(headfirst),1,fin);
  if(headfirst.type!=19778)
  {
                           printf("Not BMP");
                           getch();
                           return(0);
                           }
  printf("Header %x ",headfirst.type);
  printf("%u ",headfirst.size);
  printf("%u %u ",headfirst.reserved1,headfirst.reserved2);
  printf("%u\\n",headfirst.offset); 
  fin=fopen("C:/Dev-Cpp/1.bmp","rb+");         
  fread(&headsecond,sizeof(headsecond),1,fin);

  //Read Image Information Directory
  printf("IFD %u",headsecond.size);
  printf("%d %d %u %u %u %d %d %u %u\\n",headsecond.width,headsecond.height,headsecond.height,headsecond.bits,headsecond.compression,headsecond.imagesize,headsecond.xresolution,headsecond.yresolution,headsecond.ncolors,headsecond.impcolors);
  
  //Read Image Pixel Values
  fin=fopen("C:/Dev-Cpp/1.bmp","rb+");
  if(fin==0)
  {return(0);
  }
  for(i=0;i<headfirst.offset;i++)
  {
                                 ch=getc(fin);//Remove Offset
  }
  i=0;
  while ((ch=fgetc(fin))!=EOF)
  {
       mat\[i\]=(int)ch;
       i++;
  }
 //mat\[\] gives me the whole array of pixels in the image
 //Now I need to co

CPallini

What is the misbehaviour? Please be specific in your posts. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

Hamid Taebi

And your question we need to use of your code or it doesnt work ?

Of one Essence is the human race thus has Creation put the base One Limb impacted is sufficient For all Others to feel the Mace (Saadi )

KarstenK

try it here http://www.rentacoder.com/[^] or start learning programming.

Press F1 for help or google it. Greetings from Germany

Baltoro

...Since, you are trying to read a Bitmap (presumably stored on disk), I'm assuming that you are attempting to write Windows code. Your posted code example has numerous errors. You should start by reading up on the: Bitmap Storage Format, MSDN[^]. This will explain the overall data structure of a bitmap file stored on your computer. You should become familiar with the Bitmap header structure, so that you can read the bitmap file correctly. Here is the reference for the Bitmap Header Types[^]. You should read the headers first to be sure that the image is, in fact, a 24-bit bitmap type (there are numerous variations). The preferred method is to open the bitmap file with, CreateFile. Then you can read the byte arrays in whatever way is appropriate to your applicatrion.

Mitesh Karwa

The code does not execute

Mitesh Karwa

The code does not execute... The image is read right to left i believe, not left to right

CPallini

Mitesh Karwa wrote:

The code does not execute...

Mitesh Karwa wrote:

The image is read right to left i believe, not left to right

The above behaviours looks quite incompatible... :rolleyes:

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

Mitesh Karwa

Actually the problem is that when i write to the image file, nothing gets written on the image. Do I need to include the image header and all again. If yes, how will I know the address it will point to and all that. What I have done is, in the target directory, right click and go to new -> Bitmap Image. Renamed it as 1.bmp I'm trying to write the array that contains my grayscale image to that file 1.bmp... But the code does not work. Somehow nothing gets written on it

Mitesh Karwa

I'm afraid I did not get you... Actually, I could not get the image written on the file I meant to. So, the code does not execute. And I am also doing the same thing in MATLAB. I got the pixel values there using imread command. On comparing, i found that the image is being read right to left. That was also my question... does imread read the image from right to left... Hope I am being clearer now. Please help me

Mitesh Karwa

The preferred method is to open the bitmap file with, CreateFile. I am not doing Windows Programming. I am doing a project on face recognition on C++. How do I use CreateFile on C++? Any useful links for that might be helpful

CPallini

There is a not of stuff on the web showing how to load a bitmap file, see, for instance [^]. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

Mitesh Karwa

I am not working on Windows Programming. In fact I have no idea about it. Still anyways, thanks for your help. It's very helpful. I'll try to fix it from here on. But what about my problem reading the image back after I have done manipulations on it... How do I write it back to another file?

XcentY

I'm actually building a BMP Reader in C And I came accross your code. I'm only in the beginning and already changed some stuff. First when you put if(headfirst.type!=19778) I see that you're not taking ENDIAN in account. I made some functions to reorder the bytes.