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	invert.c (2295B)
	---
	1 /*
	2 * 0BSD-License
	3 *
	4 * (c) 2017 Laslo Hunhold <[email protected]>
	5 *
	6 * Permission to use, copy, modify, and/or distribute this software for
	7 * any purpose with or without fee is hereby granted.
	8 *
	9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
	10 * WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
	11 * WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
	12 * AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
	13 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
	14 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
	15 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
	16 * PERFORMANCE OF THIS SOFTWARE.
	17 */
	18 #include <arpa/inet.h>
	19
	20 #include <errno.h>
	21 #include <stdint.h>
	22 #include <stdio.h>
	23 #include <string.h>
	24
	25 #define LEN(x) (sizeof (x) / sizeof *(x))
	26
	27 static void
	28 invert(uint16_t rgba[4])
	29 {
	30 rgba[0] = UINT16_MAX - rgba[0];
	31 rgba[1] = UINT16_MAX - rgba[1];
	32 rgba[2] = UINT16_MAX - rgba[2];
	33 }
	34
	35 int
	36 main(int argc, char *argv[])
	37 {
	38 uint32_t hdr[4], width, height, i, j, k;
	39 uint16_t rgba[4];
	40
	41 /* arguments */
	42 if (argc != 1) {
	43 fprintf(stderr, "usage: %s\n", argv[0]);
	44 return 1;
	45 }
	46
	47 /* read header */
	48 if (fread(hdr, sizeof(*hdr), LEN(hdr), stdin) != LEN(hdr)) {
	49 goto readerr;
	50 }
	51 if (memcmp("farbfeld", hdr, sizeof("farbfeld") - 1)) {
	52 fprintf(stderr, "%s: invalid magic value\n", argv[0]);
	53 return 1;
	54 }
	55 width = ntohl(hdr[2]);
	56 height = ntohl(hdr[3]);
	57
	58 /* write data */
	59 if (fwrite(hdr, sizeof(*hdr), LEN(hdr), stdout) != 4) {
	60 goto writerr;
	61 }
	62
	63 for (i = 0; i < height; i++) {
	64 for (j = 0; j < width; j++) {
	65 if (fread(rgba, sizeof(*rgba), LEN(rgba),
	66 stdin) != LEN(rgba)) {
	67 goto readerr;
	68 }
	69 for (k = 0; k < 4; k++) {
	70 rgba[k] = ntohs(rgba[k]);
	71 }
	72
	73 invert(rgba);
	74
	75 for (k = 0; k < 4; k++) {
	76 rgba[k] = htons(rgba[k]);
	77 }
	78 if (fwrite(rgba, sizeof(*rgba), LEN(rgba),
	79 stdout) != LEN(rgba)) {
	80 goto writerr;
	81 }
	82 }
	83 }
	84
	85 /* clean up */
	86 if (fclose(stdout)) {
	87 fprintf(stderr, "%s: fclose: %s\n", argv[0],
	88 strerror(errno));
	89 return 1;
	90 }
	91
	92 return 0;
	93 readerr:
	94 fprintf(stderr, "%s: fread: Unexpected EOF\n", argv[0]);
	95 return 1;
	96 writerr:
	97 fprintf(stderr, "%s: fwrite: %s\n", argv[0], strerror(errno));
	98 return 1;
	99 }