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My version of resize less comfortable. This was super frustrating to sort out!
/*
Takes in a bmp file
and copies it to a new file
*/
#include <stdio.h>
#include <stdlib.h> // abs()
#include "bmp.h" // bmp structs
int main(int argc, char* argv[])
{
// ensure proper usage
if (argc != 4)
{
printf("Usage: ./copy n infile outfile\n");
return 1;
}
// remember filenames
int factor = atoi(argv[1]);
char* infile = argv[2];
char* outfile = argv[3];
// open input file
FILE* inptr = fopen(infile, "r");
if (inptr == NULL)
{
printf("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;
}
//create outfile bf and bi
BITMAPFILEHEADER obf;
BITMAPINFOHEADER obi;
// first make a copy of the input headers
obf = bf;
obi = bi;
// update values
obi.biWidth *= factor;
obi.biHeight *= factor;
int inPadding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
int outPadding = (4 - (obi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
obi.biSizeImage =
((sizeof(RGBTRIPLE) * obi.biWidth) + outPadding)
* abs(obi.biHeight);
obf.bfSize = obi.biSizeImage +
sizeof(BITMAPFILEHEADER) +
sizeof(BITMAPINFOHEADER);
// write headers to outfile
fwrite(&obf, sizeof(BITMAPFILEHEADER), 1, outptr);
fwrite(&obi, sizeof(BITMAPINFOHEADER), 1, outptr);
// create buffer to hold a scanline's worth of pixels
RGBTRIPLE * scanline = malloc(sizeof(RGBTRIPLE) * obi.biWidth);
for(int i = 0; i < abs(bi.biHeight); i++)
{
int pixel_tracker = 0;
for(int j = 0; j < bi.biWidth; j++)
{
// create placeholder for pixel
RGBTRIPLE pixel;
// read in the pixel
fread(&pixel, sizeof(RGBTRIPLE), 1, inptr);
for(int k = 0; k < factor; k++)
{
// add to the buffer factor times
// use pointer arithmetic
// assigning the pixel in the correct place
// by leveraging the current value of pixel_tracker
*(scanline + pixel_tracker) = pixel;
pixel_tracker++;
}
}
// fseek over input padding to get to next row
fseek(inptr, inPadding, SEEK_CUR);
// loop through adding rows based on resize factor
for(int l = 0; l < factor; l++)
{
fwrite(scanline, sizeof(RGBTRIPLE), obi.biWidth, outptr);
// also add padding to each row inside the loop manually
for(int m = 0; m < outPadding; m++)
{
fputc(0x00, outptr);
}
}
}
//free buffer
free(scanline);
// close infile
fclose(inptr);
// close outfile
fclose(outptr);
return 0;
}
@codersguild

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@codersguild codersguild commented Oct 3, 2018

Sorry, I was reading through your code. It looks good I must say.

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