diff options
| -rw-r--r-- | farbfeld.5 | 101 |
1 files changed, 73 insertions, 28 deletions
@@ -52,72 +52,117 @@ and inherent complexity involved in handling common image formats (PNG, JPEG, GIF,...), having to rely on bloated libraries while not being able to focus on the task at hand for a given image processing problem. .Sh EXAMPLES -Below is an example for a color inverter usable in a pipeline. No external -libraries other than libc are needed to handle the image data: +The following code listing +.Em invert.c +is a ready-to-use color inverter with all necessary error handling and +reporting. This program can be integrated into a farbfeld pipeline as +follows: +.Pp +$ png2ff < image.png | invert | ff2png > image-inverted.png +.Pp +It shall be noted here that due to the simplicity of the format no +external libraries are needed to handle the farbfeld image data. The +0BSD-License gives you the freedom to throw away the license block and +just use the code as you wish. Happy hacking! .Bd -literal -offset left +/* + * 0BSD-License + * + * (c) 2017 Laslo Hunhold <dev@frign.de> + * + * Permission to use, copy, modify, and/or distribute this software for + * any purpose with or without fee is hereby granted. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL + * WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED + * WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE + * AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL + * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR + * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER + * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR + * PERFORMANCE OF THIS SOFTWARE. + */ #include <arpa/inet.h> +#include <errno.h> #include <stdint.h> #include <stdio.h> -#include <stdlib.h> #include <string.h> +#define LEN(x) (sizeof (x) / sizeof *(x)) + +static void +invert(uint16_t rgba[4]) +{ + rgba[0] = UINT16_MAX - rgba[0]; + rgba[1] = UINT16_MAX - rgba[1]; + rgba[2] = UINT16_MAX - rgba[2]; +} + int main(int argc, char *argv[]) { - uint32_t width, height, i, j, k; + uint32_t hdr[4], width, height, i, j, k; uint16_t rgba[4]; - uint8_t hdr[strlen("farbfeld") + 2 * sizeof(uint32_t)]; - if (argc > 1) { + /* arguments */ + if (argc != 1) { fprintf(stderr, "usage: %s\\n", argv[0]); return 1; } - if (fread(hdr, 1, sizeof(hdr), stdin) != sizeof(hdr)) { - fprintf(stderr, "incomplete header\\n"); - return 1; + /* read header */ + if (fread(hdr, sizeof(*hdr), LEN(hdr), stdin) != LEN(hdr)) { + goto readerr; } - if (memcmp("farbfeld", hdr, strlen("farbfeld"))) { - fprintf(stderr, "invalid magic\\n"); + if (memcmp("farbfeld", hdr, sizeof("farbfeld") - 1)) { + fprintf(stderr, "%s: invalid magic value\\n", argv[0]); return 1; } - width = ntohl(*((uint32_t *)(hdr + 8))); - height = ntohl(*((uint32_t *)(hdr + 12))); + width = ntohl(hdr[2]); + height = ntohl(hdr[3]); - if (fwrite(hdr, 1, sizeof(hdr), stdout) != sizeof(hdr)) { - fprintf(stderr, "write error\\n"); - return 1; + /* write data */ + if (fwrite(hdr, sizeof(*hdr), LEN(hdr), stdout) != 4) { + goto writerr; } for (i = 0; i < height; i++) { for (j = 0; j < width; j++) { - if (fread(rgba, sizeof(uint16_t), 4, - stdin) != 4) { - fprintf(stderr, "unexpected EOF\\n"); - return 1; + if (fread(rgba, sizeof(*rgba), LEN(rgba), + stdin) != LEN(rgba)) { + goto readerr; } for (k = 0; k < 4; k++) { rgba[k] = ntohs(rgba[k]); } - /* invert colors */ - rgba[0] = 65535 - rgba[0]; - rgba[1] = 65535 - rgba[1]; - rgba[2] = 65535 - rgba[2]; + invert(rgba); for (k = 0; k < 4; k++) { rgba[k] = htons(rgba[k]); } - if (fwrite(rgba, sizeof(uint16_t), 4, - stdout) != 4) { - fprintf(stderr, "write error\\n"); - return 1; + if (fwrite(rgba, sizeof(*rgba), LEN(rgba), + stdout) != LEN(rgba)) { + goto writerr; } } } + /* clean up */ + if (fclose(stdout)) { + fprintf(stderr, "%s: fclose: %s\\n", argv[0], + strerror(errno)); + return 1; + } + return 0; +readerr: + fprintf(stderr, "%s: fread: Unexpected EOF\\n", argv[0]); + return 1; +writerr: + fprintf(stderr, "%s: fwrite: %s\\n", argv[0], strerror(errno)); + return 1; } .Ed .Sh SEE ALSO |