Thread: Exporting bmp file

Hi. I don't understand why I can't export this bmp file properly. I just basically got a bmp file name from the user, transferred the data to a double pointer and copied it back to a new file to be saved.
But when I run it, and try to open the new image, it says, 'invalid image format'. I don't know what to do anymore
Help pls.

ifile is where i fopened the input file which is lena.bmp
Thanks

Code:

char **idata = malloc( sizeof( char *)*( (*iheader).height) );
    int irow, icol, count = 0;
    int a = 0;
    for ( irow = 0; irow < (*iheader).height; irow++ ){
        idata[irow] = malloc( sizeof(char)*( roundto4s( (iheader->width)*3 ) ) );
    }
    //STORING IMAGE DATA FOR REALZZZ
    for ( irow = 0; irow < ( *iheader ).height; irow++ ){
        for ( icol = 0; icol < roundto4s( ( ( *iheader ).width )*3); icol++ ){
            a = fread( &(idata[irow][icol]), 1, 1, ifile);
            if ( a == 1 )
                count++;
        }
    }
    if ( count != iheader->sizeimage)
        printf("a = %d. HAHAHAHA loser.\n", a);
    
    printf("%c", idata[100][100]);
    
    
    //EXPORTING IMAGE
    FILE *nfile;
    count = 0;
    nfile = fopen("lena_edited.bmp", "w+b");
    fseek(ifile, 0, SEEK_SET);
    a = fwrite(ifile, 1, fheader->offset, nfile);
        if ( a != fheader->offset )
            printf("a = %d. HAHAHAHA loser.\n", a);
    fseek(ifile, fheader->offset, SEEK_SET);
    a = fwrite(ifile, 1, iheader->sizeimage, nfile);
        if ( a != iheader->sizeimage )
            printf("a = %d. HAHAHAHA loser.\n", a);

Oh, the printf thing was just out of curiousity what would appear. please ignore it.

Code:

for ( irow = 0; irow < (*iheader).height; irow++ ){
        idata[irow] = malloc( sizeof(char)*( roundto4s( (iheader->width)*3 ) ) );
    }

that part make sures that i allocate memory that's a multiple of 4 doesnt it? Since I made a roundto4s( int a ); function that rounds stuff to multiples of four.

So aren't I reading or writing the padding too?

You need to post the smallest runnable program that demonstrates the problem so we can see all the details and actually run it.