I'm trying to figure out how to finish my resize.c and am feeling pretty stuck. Right now, when I run the resize.c to change small by a factor of 4, I get a green square of the correct size (but with no white in the middle). When I take out "fseek(inptr, -(newPadding+bi_out.biWidth), SEEK_CUR);" I get something closer to the correct output - the box you see below that has a white rectangle that has been resized horizontally but not vertically.

output without fseek

I believe that my headers are correct and, logically, it seems like the problem would be with the for loop that is responsible for the vertical resize. Yet I'm troubled by the fact that my attempt to move back to the beginning of the horizontal line with fseek seems to make matters worse.

Any suggestions would be appreciated.

// write outfile's BITMAPFILEHEADER
fwrite(&bf_out, sizeof(BITMAPFILEHEADER), 1, outptr);

// write outfile's BITMAPINFOHEADER
fwrite(&bi_out, sizeof(BITMAPINFOHEADER), 1, outptr);

// iterate over infile's scanlines, up to the abs value of the original height
for (int i = 0; i < origHeight2; i++)
    for (int z = 0; z<n; z++)

        for( int j = 0; j < origWidth; j++)
            //temporary storage
            RGBTRIPLE triple;
            // read RGB triple from infile
            fread(&triple, sizeof(RGBTRIPLE), 1, inptr);

            // write RGB triple to outfile
            for( int k = 0; k < n; k++)
            fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
         // skip over padding, if any
        fseek(inptr, padding, SEEK_CUR);
        //add padding back
        for (int l = 0; l < newPadding; l++)
            fputc(0x00, outptr);
        //return to beginning of line
        fseek(inptr, -(newPadding+bi_out.biWidth), SEEK_CUR);

All of the issues lie in the last fseek. First, this fseek repositions the pointer for the input file, so why does it use the padding for the output file?

Second, you need to think about when this has to be done. Do you need to do this after the last copy of each line has been processed and the code needs to move to the next line?

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