I'm struggling a bit with pset4, it would be really helpful if I can get some advice. It does enlarge the size but create a faulty image.
I am trying to use 'recopy' method here. Could anybody help me with some advice?
Also, I was wondering why abs
is used for abs(bi.biHeight)
. Isn't biHeight
already always positive integer?
int main(int argc, char *argv[]) { // ensure proper usage if (argc != 4 || atoi(argv[1]) > 100 || atoi(argv[1]) < 1 ) { fprintf(stderr, "Usage: ./copy n infile outfile\n"); return 1; }
// remember filenames
int n = atoi(argv[1]);
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;
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;
}
// original padding
int padding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
bi.biWidth *= n;
bi.biHeight *= n;
// new padding
int newpadding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
bi.biSizeImage = ((sizeof(RGBTRIPLE) * bi.biWidth) + newpadding) * abs(bi.biHeight);
bf.bfSize = bi.biSizeImage + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
// write outfile's BITMAPFILEHEADER
fwrite(&bf, sizeof(BITMAPFILEHEADER), 1, outptr);
// write outfile's BITMAPINFOHEADER
fwrite(&bi, sizeof(BITMAPINFOHEADER), 1, outptr);
// read infile's scanline, pixel by pixel
for (int i = 0, biHeight = abs(bi.biHeight); i < biHeight; i++)
{
for (int j = 0; j < bi.biWidth; j++) //bi.biWidth[0]......bi.biWidth[j].
{
// temporary storage
RGBTRIPLE triple;
// read RGB triple from infile
fread(&triple, sizeof(RGBTRIPLE), 1, inptr);
// write RGB triple to outfile
fwrite(&triple, sizeof(RGBTRIPLE), n, outptr);
}
// skip over padding, if any
fseek(inptr, padding, SEEK_CUR);
// insert padding if needed
for (int k = 0; k < newpadding; k++)
{
fputc(0x00, outptr);
}
// go back the scanline
for (int m = 0; m < n - 1; m++)
{
fseek(inptr, -(bi.biWidth + newpadding), SEEK_CUR);
}
}
// close infile
fclose(inptr);
// close outfile
fclose(outptr);
// success
return 0;
}