Remove/Overwrite padding - BMP C

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C

Bitmap

Hello and Merry Christmas ! I've made a program that overwrites all the colors from a 24bit bitmap (except for white) with a given one (it is said that the background is white) . The problem is that i can't remove the padding . I've read bunch of tutorials and questions and still can't manage to solve the problem . I'm asked to overwrite the padding with 0 (I don't know why , in my opinion it will make the padding black) but i'm getting in the upper-right corner always a black row of one third the size of the width..

This is the input image
http://i.stack.imgur.com/jAsW6.png[^]
This is the desired output
http://i.stack.imgur.com/aAgix.png[^]
And this is my result
http://i.stack.imgur.com/yNvqq.png[^]

Now i've seen that not even the color is right..
And here is the code :

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "bmp_header.h"

int main(void)
{
    FILE *f;
    f = fopen("captcha.bmp","rb");
    fread(&BMP_header,sizeof(BMP_header),1,f);
    fread(&BMP_info_header,sizeof(BMP_info_header),1,f);
    fseek(f,BMP_header.imageDataOffset,SEEK_SET);
    int rowSize = (BMP_info_header.bitPix * BMP_info_header.width + 31 ) /32 * 4 ;
    unsigned char *PixelArray = (unsigned char *)malloc(rowSize * abs(BMP_info_header.height));
    fread(PixelArray,sizeof(char),BMP_info_header.biSizeImage,f);
    int i,j,k,addPadding;
    int padding = 4-((BMP_info_header.width*3)%4);

    for( i = 0; i<abs(BMP_info_header.height); i++)

    {
                   for(j = 0 ; j<rowSize-padding; j+= 3)
                  {
                        int offset = i * (rowSize-padding) + j;
                        if((PixelArray[offset] != 255 ) && (PixelArray[offset+1] != 255) && (PixelArray[offset+2] != 255))
                       {    //it is asked to use this RGB value (69,106,671)
                            PixelArray[offset] = 69;
                            PixelArray[offset+1] = 106;
                            PixelArray[offset+2] = 671;
                       }
                  }

                  for (addPadding = 0 ; addPadding < padding ; addPadding ++)

                        PixelArray[ i * (rowSize+padding) + j  ] = 255;

    }



    f = fopen("result.bmp","wb");
    fwrite(&BMP_header,sizeof(BMP_header),1,f);
    fwrite(&BMP_info_header,sizeof(BMP_info_header),1,f);
    fwrite(PixelArray,rowSize * abs(BMP_info_header.height),1,f);
    fclose(f);
    free(PixelArray);


    return 0;
}

Here is "bmp_header.h" 's content :

#pragma pack(1)

struct bmp_fileheader
{
    unsigned char  fileMarker1; /* 'B' */
    unsigned char  fileMarker2; /* 'M' */
    unsigned int   bfSize; /* File's size */
    unsigned short unused1;
    unsigned short unused2;
    unsigned int   imageDataOffset; /* Offset to the start of image data */
}BMP_header,BMP_header_out;

struct bmp_infoheader
{
    unsigned int   biSize; /* Size of the info header - 40 bytes */
    signed int     width; /* Width of the image */
    signed int     height; /* Height of the image */
    unsigned short planes;
    unsigned short bitPix;
    unsigned int   biCompression;
    unsigned int   biSizeImage; /* Size of the image data */
    int            biXPelsPerMeter;
    int            biYPelsPerMeter;
    unsigned int   biClrUsed;
    unsigned int   biClrImportant;
}BMP_info_header,BMP_info_header_out;

#pragma pack()

Any help would be very much appreciated :)