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util.c - ff2txt - farbfeld image to plain text visualization |
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git clone git://bitreich.org/ff2txt git://enlrupgkhuxnvlhsf6lc3fziv5h2hhfrinws65d7roiv6bfj7d652fid.onion/ff2txt (git://bitreich.org) |
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README |
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--- |
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util.c (822B) |
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--- |
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1 #include <arpa/inet.h> |
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2 |
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3 #include <stdint.h> |
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4 #include <stdlib.h> |
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5 #include <stdio.h> |
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6 #include <string.h> |
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7 |
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8 #include "util.h" |
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9 |
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10 void |
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11 err(char *msg) |
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12 { |
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13 perror(msg); |
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14 exit(1); |
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15 } |
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16 |
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17 void |
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18 read_header(uint32_t *width, uint32_t *height) |
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19 { |
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20 uint32_t header[4]; |
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21 |
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22 if (fread(header, sizeof(*header), LEN(header), stdin) != LEN(header)) |
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23 err("fread"); |
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24 |
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25 if (memcmp("farbfeld", header, sizeof("farbfeld") - 1)) |
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26 err("invalid magic value\n"); |
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27 |
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28 *width = ntohl(header[2]); |
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29 *height = ntohl(header[3]); |
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30 |
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31 if (width == 0 || height == 0) |
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32 err("empty image"); |
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33 } |
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34 |
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35 static uint16_t |
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36 col_blend(struct col col) |
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37 { |
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38 int16_t sum; |
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39 |
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40 /* divide first to avoid overflow */ |
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41 sum = ntohs(col.red) / 3; |
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42 sum += ntohs(col.green) / 3; |
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43 sum += ntohs(col.blue) / 3; |
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44 |
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45 return sum; |
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46 } |
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47 |
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48 int |
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49 col_is_bright(struct col col) |
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50 { |
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51 return col_blend(col) >= UINT16_MAX / 2; |
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52 } |
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