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I am stuck on resize (less). The problem is I think, header of new bmp is always corrupted no matter what. My code compiles and I tried to identify error using debug50 to no avail. Please help me regarding this. My code is below:

#include <stdio.h>
#include <stdlib.h>
#include "bmp.h"

int main(int argc, char *argv[])
{
    // ensure proper usage
    if (argc != 4)
    {
        fprintf(stderr, "Usage: n infile outfile\n");
        return 1;
    }

    // remember filenames
    char *infile = argv[2];
    char *outfile = argv[3];

    //store factor n
    int n = atoi(argv[1]);

    // open input file
    FILE *inptr = fopen(infile, "r");
    if (inptr == NULL)
    {
        fprintf(stderr, "Could not open %s.\n", infile);
        return 2;
    }

    // open output file
    FILE *outptr = fopen(outfile, "w");
    if (outptr == NULL)
    {
        fclose(inptr);
        fprintf(stderr, "Could not create %s.\n", outfile);
        return 3;
    }

    // read infile's BITMAPFILEHEADER
    BITMAPFILEHEADER bf;
    fread(&bf, sizeof(BITMAPFILEHEADER), 1, inptr);

    // read infile's BITMAPINFOHEADER
    BITMAPINFOHEADER bi;
    fread(&bi, sizeof(BITMAPINFOHEADER), 1, inptr);

    // ensure infile is (likely) a 24-bit uncompressed BMP 4.0
    if (bf.bfType != 0x4d42 || bf.bfOffBits != 54 || bi.biSize != 40 ||
        bi.biBitCount != 24 || bi.biCompression != 0)
    {
        fclose(outptr);
        fclose(inptr);
        fprintf(stderr, "Unsupported file format.\n");
        return 4;
    }


    // Store original width and height
    LONG oBiWidth = bi.biWidth;
    LONG oBiHeight = bi.biHeight;

    //Update BITMAPINFOHEADER Width and Height
    biNew.biWidth *= n;
    biNew.biHeight *= n;

    // determine padding for scanlines
    int padding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;

    //Update biSizeImage
    bi.biSizeImage=((sizeof(RGBTRIPLE) * bi.biWidth) + padding) * abs(bi.biHeight);

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

    //Update BITMAPFILEHEADER
    bf.bfSize = bi.biSizeImage + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

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

    //TODO: Store old Height and Width that are two be used in nested for loops

    // iterate over infile's scanlines
    for (int i = 0, biHeight = abs(oBiHeight); i < biHeight; i++)
    {
        // iterate over pixels in scanline
        for (int j = 0; j < oBiWidth; j++)
        {
            // temporary storage
            RGBTRIPLE triple;

            // read RGB triple from infile
            fread(&triple, sizeof(RGBTRIPLE), 1, inptr);

            // write RGB triple to outfile n times
            for (int m=0; m<n; m++)
            {
                fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);    
            }
        }

        // skip over padding, if any
        fseek(inptr, padding, SEEK_CUR);

        // then add it back (to demonstrate how)
        for (int k = 0; k < padding; k++)
        {
            fputc(0x00, outptr);
        }
    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // success
    return 0;
}
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For starters, the code doesn't compile because of biNew.* vars. But ignoring that, have you looked at the actual hex data in the header to see what it looks like? The browser in the IDE does have a hex display function. (See whodunit insturctions on how.)

BTW, which header is supposed to be written out first, bi or bf???? ;-)

If this answers your question, please click on the check mark to accept. Let's keep up on forum maintenance. ;-)

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  • Ok, so ..New was added by mistake. However this doesn't caused the problem. And yes I just figured out that BITMAPFILEHEADER has to be written first. Thank you so much :)
    – Raffay
    Jul 23 '18 at 9:07

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