Epoch.

COPYING

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+ISC License
+
+Copyright (c) 2018, Adrian "vifino" Pistol
+
+Permission to use, copy, modify, and/or distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+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.

Makefile

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+CC ?= cc
+CFLAGS ?= -Os
+CPPLAGS += -pedantic -Wall
+
+BINS=ff-glitch
+
+all: $(BINS)
+
+ff-glitch: ff-glitch.c
+	$(CC) $(CPPFLAGS) $(CFLAGS) $(LDFLAGS) -o ff-glitch $^
+
+clean:
+	rm $(BINS)

ff-glitch.c

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+// ┳━┓┳━┓  ┏━┓┳  o┏┓┓┏━┓┳ ┳
+// ┣━ ┣━ ━━┃ ┳┃  ┃ ┃ ┃  ┃━┫
+// ┇  ┇    ┇━┛┇━┛┇ ┇ ┗━┛┇ ┻
+// ff-glitch: the farbfeld glitcher.
+// usage: <farbfeld source> | ff-glitch | <farbfeld sink>
+// thanks to xero for the idea! you rock.
+// made by vifino. ISC (C) vifino 2018
+
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <sys/time.h>
+#include <arpa/inet.h>
+
+// TODO: replace ntohl
+
+static uint32_t w, h;
+static unsigned char buf[64] = {0};
+static unsigned char img;
+static struct timeval tv;
+
+typedef struct {
+	unsigned short r, g, b, a;
+} pixel;
+
+// IO helpers.
+static inline void bread(int bytes) {
+	if (!fread(buf, bytes, 1, stdin)) {
+		fprintf(stderr, "wanted more bytes, didn't get any?\n");
+		exit(1);
+	}
+}
+
+static inline void bwrite(unsigned char* buffer, size_t bytes) {
+	if (!fwrite(buffer, bytes, 1, stdout)) {
+		fprintf(stderr, "write failed.\n");
+		exit(1);
+	}
+}
+
+// random helper, random from 0-n, inclusive.
+// tries to get evenly spread out random.
+unsigned int randn(unsigned int n) {
+	if (!n) return 0;
+	if (n == RAND_MAX) return rand();
+	n++;
+	long end = RAND_MAX / n;
+	end *= n;
+	int r;
+	while ((r = rand()) >= end);
+	return r % n;
+}
+
+// Glitch a short.
+#define GLITCHPX() randn(2 * UINT8_MAX)
+
+int main(int argc, char* argv[]) {
+	// TODO: parse argv[1] for range;
+	unsigned int glitches = 40 + randn(50);
+
+	bread(8);
+	if (strcmp(buf, "farbfeld") != 0) {
+		fprintf(stderr, "stdin is not a farbfeld image?\n");
+		return 1;
+	}
+	bwrite(buf, 8);
+
+	// seed like a dumbass.
+	if (gettimeofday(&tv, NULL)) {
+		fprintf(stderr, "failed to get the time? that's messed up.\n");
+		return 2;
+	}
+	srand(tv.tv_usec);
+
+	// parse width and height
+	bread(8);
+	uint32_t w = ntohl(*(uint32_t*)buf);
+	uint32_t h = ntohl(*((uint32_t*)(buf + 4)));
+	if (!w && !h) {
+		fprintf(stderr, "image size has zero dimension? %i*%i\n", w, h);
+		return 1;
+	}
+	bwrite(buf, 8);
+
+	unsigned int pxn;
+	unsigned int end = w*h;
+	unsigned int trash = 0;
+	unsigned int skipped = 0;
+	int glitchpx = 0;
+	unsigned short gv;
+	unsigned char gp = 0;
+	pixel glitchp;
+	for(pxn = 0; pxn < end; pxn++) {
+		if (randn(end / glitches) == 0) {
+			// glitch it. glitch it hard.
+			trash = randn(end / 10 / glitches);
+			if (randn(1) == 0) {
+				glitchpx = randn((end * 4) / glitches);
+				gp = randn(2);
+				gv = GLITCHPX();
+			}
+		}
+
+		if (trash) {
+			// trash it.
+			pxn = pxn + trash - 1;
+			while (trash > 1) {
+				if (randn(1) == 0) {
+					bread(8); // throw away
+				} else {
+					skipped++;
+				}
+				pixel* px = (pixel*) buf;
+				px->r = GLITCHPX();
+				px->g = GLITCHPX();
+				px->b = GLITCHPX();
+				trash--;
+				bwrite(buf, 8);
+			}
+		}
+
+		bread(8);
+		if (glitchpx) {
+			pixel* px = (pixel*) buf;
+			if ((glitchpx - 1) >= 0) {
+				switch (gp) {
+				case 0:
+					px->r = gv;
+					break;
+				case 1:
+					px->g = gv;
+					break;
+				case 2:
+					px->b = gv;
+					break;
+				}
+				glitchpx--;
+			}
+			if (glitchpx < 0) glitchpx = 0;
+		}
+
+		bwrite(buf, 8);
+	}
+	for (; skipped > 0; skipped--)
+		bread(8);
+
+	return 0;
+}