I can't seem to figure out what's wrong with my resize code - it only resizes correctly for n = 1. I've checked the header data when n = 4 compared to large.bmp, and it's the same. If anyone knows what I'm doing wrong, please let me know.
Edit: I've changed my code to make a new bf and bi, and this almost works, but not quite. If you can see the problem here, please help!
// Resizes a bmp file
#include
#include
#include "bmp.h"
int main(int argc, char *argv[])
{
// ensure proper usage
if (argc != 4)
{
fprintf(stderr, "Usage: copy n infile outfile\n");
return 1;
}
// remember filenames
int n = atoi(argv[1]);
//printf("%i", n);
char *infile = argv[2];
char *outfile = argv[3];
// 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, nbf;
fread(&bf, sizeof(BITMAPFILEHEADER), 1, inptr);
nbf = bf;
// read infile's BITMAPINFOHEADER
BITMAPINFOHEADER bi, nbi;
fread(&bi, sizeof(BITMAPINFOHEADER), 1, inptr);
nbi = bi;
// 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;
}
// int ogWidth = bi.biWidth;
// int ogHeight = bi.biHeight;
int ogPadding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
printf("og Padding: %i\n", ogPadding);
// multiply width and height by n
// this is where the problem is?
nbi.biWidth = bi.biWidth * n;
nbi.biHeight = bi.biHeight * n;
// determine padding for scanlines
int newPadding = (4 - (nbi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4; // Here
printf("new Padding: %i\n", newPadding);
nbi.biSizeImage = ((sizeof(RGBTRIPLE) * nbi.biWidth) + newPadding) * abs(nbi.biHeight); // Here
nbf.bfSize = nbi.biSizeImage + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
// incorrect because bi.biWidth is still og
// write outfile's BITMAPFILEHEADER
fwrite(&nbf, sizeof(BITMAPFILEHEADER), 1, outptr);
// write outfile's BITMAPINFOHEADER
fwrite(&nbi, sizeof(BITMAPINFOHEADER), 1, outptr);
// iterate over infile's scanlines
for (int i = 0, biHeight = abs(bi.biHeight); i < biHeight; i++)
{
for (int o = 0; o < n - 1; o++)
{
printf("Yay %i\n", o);
// iterate over pixels in scanline
for (int j = 0; j < bi.biWidth; j++) // Here
{
// temporary storage
RGBTRIPLE triple;
// read RGB triple from infile
fread(&triple, sizeof(RGBTRIPLE), 1, inptr);
// write RGB triple to outfile
for (int p = 0; p < n; p++){
fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
//printf("in loop %i", p);
}
}
// add padding
for (int k = 0; k < newPadding; k++)
{
fputc(0x00, outptr);
printf("Padding\n");
}
fseek(inptr, -1 * bi.biWidth, SEEK_CUR); // Here
}
// iterate over pixels in scanline
for (int j = 0; j < bi.biWidth; j++) // Here
{
// temporary storage
RGBTRIPLE triple;
// read RGB triple from infile
fread(&triple, sizeof(RGBTRIPLE), 1, inptr);
// write RGB triple to outfile
for (int p = 0; p < n; p++){
fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
//printf("in loop %i", p);
}
}
// add padding
for (int k = 0; k < newPadding; k++)
{
fputc(0x00, outptr);
//printf("Padding");
}
// skip over padding, if any
fseek(inptr, ogPadding, SEEK_CUR);
// // Skip back to previous line if necessary
// int o = (i + 1) % n;
// printf("o: %i\n", o);
// if (o > 0)
// {
// int skip = bi.biWidth + ogPadding;
// printf("skip: %i\n", skip);
// fseek(inptr, -4, SEEK_CUR);
// //printf("Gotcha\n");
// }
}
// close infile
fclose(inptr);
// close outfile
fclose(outptr);
// success
return 0;
}