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37 lines (31 loc) · 806 Bytes
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double.c
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37 lines (31 loc) · 806 Bytes
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#include <assert.h>
#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[])
{
FILE *src = fopen(argv[1], "rb");
char line[9999], m;
int w, h, f, i;
assert(src);
fgets(line, 9999, src);
assert(0 == strcmp(line, "P6\n") || 0 == strcmp(line, "P5\n"));
m = line[1];
fgets(line, 9999, src);
assert(2 == sscanf(line, "%d %d", &w, &h));
fgets(line, 9999, src);
assert(1 == sscanf(line, "%d", &f));
assert(3 * w < 9999);
assert(9 <= printf("P%c\n%d %d\n%d\n", m, w, 2 * h, f));
f = (m == '5') ? 1 : 3;
for (i = 0; i < h; ++i)
{
assert(f * w == fread(line, 1, f * w, src));
assert(f * w == fwrite(line, 1, f * w, stdout));
assert(f * w == fwrite(line, 1, f * w, stdout));
}
h = ftell(src);
fseek(src, 0, SEEK_END);
assert(h == ftell(src));
fclose(src);
return 0;
}