Expert: Prince M. Premnath - 12/11/2006

Question
Sir, Thank for your reply. Another question, how can i use malloc function to allocate a memory space for a variable?
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The text above is a follow-up to ...

-----Question-----
Sir, my question is : By using C language, how to create a new image(.bmp) when i have all the raster data of a original image(.bmp)?

Thank you in advance!

-----Answer-----
Dear Wei!
 Really i cant understand your question , but one thing i wish to tell you now  , we can manipulate any type of files using C  ,( say JPEG  ,and so on ) but the only thing we needs to know is about its internal file structure ,ie how the file is organized , how the data's are packed and other informations regarding to file operations, ( The file structure is always available in starting few bytes in a file ) , Using that data's you can easily duplicate , create , or manipulate any kind of files!

Regards !
Prince M. Premnath.


Answer
Dear Wei!

Here i got yet another chance to clear your doubt ! regardng BMP file processing !

I supposed to answer one questioner using a cmplete C Program that will display the BMP file on screen !

Here ill present you the program !

#include <alloc.h>
#include <conio.h>
#include <graphics.h>
#include <stdio.h>
#include <stdlib.h>


struct BMP
{
  char Type[2];          //File type. Set to "BM".
  unsigned long Size;     //Size in BYTES of the file.
  unsigned long Reserved;      //Reserved. Set to zero.
  unsigned long OffSet;   //Offset to the data.
  unsigned long headsize; //Size of rest of header. Set to 40.
  unsigned long Width;     //Width of bitmap in pixels.
  unsigned long Height;     //  Height of bitmap in pixels.
  unsigned int  Planes;    //Number of Planes. Set to 1.
  unsigned int  BitsPerPixel;       //Number of Bits per pixels.
  unsigned long Compression;   //Compression. Usually set to 0.
  unsigned long SizeImage;  //Size in bytes of the bitmap.
  unsigned long XPixelsPreMeter;     //Horizontal pixels per meter.
  unsigned long YPixelsPreMeter;     //Vertical pixels per meter.
  unsigned long ColorsUsed;   //Number of colors used.
  unsigned long ColorsImportant;  //Number of "important" colors.
};

int ShowBMP(int x, int y, char* FileName)
{
    int b,a;
    BMP Obj;

    unsigned char* Datas;
    int in=0;
    unsigned char c=0;
    FILE * fp;

    fp = fopen(FileName,"rb");
    if(!fp){
    printf("Error : Unable to open file ..");
    exit(0);
    }

    fread(&Obj, sizeof(Obj), 1, fp);
    if(Obj.BitsPerPixel!=4)  // This isn't a 16 color bmp we can read;
    {
     fclose(fp);
     printf("Error : File format not supported ..");
     exit(0);
    };
    fseek(fp,Obj.OffSet,SEEK_SET);
    Datas=(unsigned char*) calloc(Obj.Width/2+1, sizeof(unsigned char));
    for(b=Obj.Height;b>=0;b--)
    {
     fread(Datas, sizeof(unsigned char), Obj.Width/2, fp);
     c=0;
     in=0;
     for(a=0;a<=Obj.Width;a+=2)
     {
         c = (Datas[in] | 0x00) >>4;
         putpixel(a+x,b+y,c);
         c = (Datas[in] | 0xF0) & 0x0F;
         putpixel(a+1+x,b+y,c);
         in++;
     }
    }
    free (Datas);
    fclose(fp);
    return 1;
}
void main()
{
int color;
int gd , gm ;
gd = VGA ; gm = VGAHI;

initgraph(&gd,&gm,"");
ShowBMP(0,0,"tune.bmp");
getch();
closegraph();
}

Note:
  The program presented above is strictly compatible with Turbo C/C++ of any versions that support BGI.
  Here im unable to present you the bitmap file "sample.bmp"  , so i recommend you to crteate your own file to test this program !
  While creating your own file   make sure that the new file should be compatible to owr program ! other wise undesired results will come !

Regards!
Prince M. Premnath