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-rw-r--r--bin/glitch.c538
1 files changed, 538 insertions, 0 deletions
diff --git a/bin/glitch.c b/bin/glitch.c
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+++ b/bin/glitch.c
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+/* Copyright (C) 2018  June McEnroe <june@causal.agency>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <arpa/inet.h>
+#include <err.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sysexits.h>
+#include <unistd.h>
+#include <zlib.h>
+
+#define PACKED __attribute__((packed))
+
+#define CRC_INIT (crc32(0, Z_NULL, 0))
+
+static const char *path;
+static FILE *file;
+static uint32_t crc;
+
+static void readExpect(void *ptr, size_t size, const char *expect) {
+	fread(ptr, size, 1, file);
+	if (ferror(file)) err(EX_IOERR, "%s", path);
+	if (feof(file)) errx(EX_DATAERR, "%s: missing %s", path, expect);
+	crc = crc32(crc, ptr, size);
+}
+
+static void writeExpect(const void *ptr, size_t size) {
+	fwrite(ptr, size, 1, file);
+	if (ferror(file)) err(EX_IOERR, "%s", path);
+	crc = crc32(crc, ptr, size);
+}
+
+static const uint8_t Signature[8] = "\x89PNG\r\n\x1A\n";
+
+static void readSignature(void) {
+	uint8_t signature[8];
+	readExpect(signature, 8, "signature");
+	if (0 != memcmp(signature, Signature, 8)) {
+		errx(EX_DATAERR, "%s: invalid signature", path);
+	}
+}
+
+static void writeSignature(void) {
+	writeExpect(Signature, sizeof(Signature));
+}
+
+struct PACKED Chunk {
+	uint32_t size;
+	char type[4];
+};
+
+static const char *typeStr(struct Chunk chunk) {
+	static char buf[5];
+	memcpy(buf, chunk.type, 4);
+	return buf;
+}
+
+static struct Chunk readChunk(void) {
+	struct Chunk chunk;
+	readExpect(&chunk, sizeof(chunk), "chunk");
+	chunk.size = ntohl(chunk.size);
+	crc = crc32(CRC_INIT, (Byte *)chunk.type, sizeof(chunk.type));
+	return chunk;
+}
+
+static void writeChunk(struct Chunk chunk) {
+	chunk.size = htonl(chunk.size);
+	writeExpect(&chunk, sizeof(chunk));
+	crc = crc32(CRC_INIT, (Byte *)chunk.type, sizeof(chunk.type));
+}
+
+static void readCrc(void) {
+	uint32_t expected = crc;
+	uint32_t found;
+	readExpect(&found, sizeof(found), "CRC32");
+	found = ntohl(found);
+	if (found != expected) {
+		errx(
+			EX_DATAERR, "%s: expected CRC32 %08X, found %08X",
+			path, expected, found
+		);
+	}
+}
+
+static void writeCrc(void) {
+	uint32_t net = htonl(crc);
+	writeExpect(&net, sizeof(net));
+}
+
+static void skipChunk(struct Chunk chunk) {
+	uint8_t discard[chunk.size];
+	readExpect(discard, sizeof(discard), "chunk data");
+	readCrc();
+}
+
+static struct PACKED {
+	uint32_t width;
+	uint32_t height;
+	uint8_t depth;
+	enum PACKED {
+		Grayscale      = 0,
+		Truecolor      = 2,
+		Indexed        = 3,
+		GrayscaleAlpha = 4,
+		TruecolorAlpha = 6,
+	} color;
+	uint8_t compression;
+	uint8_t filter;
+	uint8_t interlace;
+} header;
+_Static_assert(13 == sizeof(header), "header size");
+
+static size_t pixelBits(void) {
+	switch (header.color) {
+		case Grayscale:      return 1 * header.depth;
+		case Truecolor:      return 3 * header.depth;
+		case Indexed:        return 1 * header.depth;
+		case GrayscaleAlpha: return 2 * header.depth;
+		case TruecolorAlpha: return 4 * header.depth;
+		default: abort();
+	}
+}
+
+static size_t pixelSize(void) {
+	return (pixelBits() + 7) / 8;
+}
+
+static size_t lineSize(void) {
+	return (header.width * pixelBits() + 7) / 8;
+}
+
+static size_t dataSize(void) {
+	return (1 + lineSize()) * header.height;
+}
+
+static void readHeader(void) {
+	struct Chunk ihdr = readChunk();
+	if (0 != memcmp(ihdr.type, "IHDR", 4)) {
+		errx(EX_DATAERR, "%s: expected IHDR, found %s", path, typeStr(ihdr));
+	}
+	if (ihdr.size != sizeof(header)) {
+		errx(
+			EX_DATAERR, "%s: expected IHDR size %zu, found %u",
+			path, sizeof(header), ihdr.size
+		);
+	}
+	readExpect(&header, sizeof(header), "header");
+	readCrc();
+	header.width = ntohl(header.width);
+	header.height = ntohl(header.height);
+	if (!header.width) errx(EX_DATAERR, "%s: invalid width 0", path);
+	if (!header.height) errx(EX_DATAERR, "%s: invalid height 0", path);
+}
+
+static void writeHeader(void) {
+	struct Chunk ihdr = { .size = sizeof(header), .type = "IHDR" };
+	writeChunk(ihdr);
+	header.width = htonl(header.width);
+	header.height = htonl(header.height);
+	writeExpect(&header, sizeof(header));
+	writeCrc();
+	header.width = ntohl(header.width);
+	header.height = ntohl(header.height);
+}
+
+static struct {
+	uint32_t len;
+	uint8_t entries[256][3];
+} palette;
+
+static void readPalette(void) {
+	struct Chunk chunk;
+	for (;;) {
+		chunk = readChunk();
+		if (0 == memcmp(chunk.type, "PLTE", 4)) break;
+		skipChunk(chunk);
+	}
+	palette.len = chunk.size / 3;
+	readExpect(palette.entries, chunk.size, "palette data");
+	readCrc();
+}
+
+static void writePalette(void) {
+	struct Chunk plte = { .size = 3 * palette.len, .type = "PLTE" };
+	writeChunk(plte);
+	writeExpect(palette.entries, plte.size);
+	writeCrc();
+}
+
+static uint8_t *data;
+
+static void readData(void) {
+	data = malloc(dataSize());
+	if (!data) err(EX_OSERR, "malloc(%zu)", dataSize());
+
+	struct z_stream_s stream = { .next_out = data, .avail_out = dataSize() };
+	int error = inflateInit(&stream);
+	if (error != Z_OK) errx(EX_SOFTWARE, "%s: inflateInit: %s", path, stream.msg);
+
+	for (;;) {
+		struct Chunk chunk = readChunk();
+		if (0 == memcmp(chunk.type, "IDAT", 4)) {
+			uint8_t *idat = malloc(chunk.size);
+			if (!idat) err(EX_OSERR, "malloc");
+
+			readExpect(idat, chunk.size, "image data");
+			readCrc();
+
+			stream.next_in = idat;
+			stream.avail_in = chunk.size;
+			int error = inflate(&stream, Z_SYNC_FLUSH);
+			free(idat);
+
+			if (error == Z_STREAM_END) break;
+			if (error != Z_OK) errx(EX_DATAERR, "%s: inflate: %s", path, stream.msg);
+
+		} else if (0 == memcmp(chunk.type, "IEND", 4)) {
+			errx(EX_DATAERR, "%s: missing IDAT chunk", path);
+		} else {
+			skipChunk(chunk);
+		}
+	}
+
+	inflateEnd(&stream);
+	if ((size_t)stream.total_out != dataSize()) {
+		errx(
+			EX_DATAERR, "%s: expected data size %zu, found %zu",
+			path, dataSize(), (size_t)stream.total_out
+		);
+	}
+}
+
+static void writeData(void) {
+	uLong size = compressBound(dataSize());
+	uint8_t *deflate = malloc(size);
+	if (!deflate) err(EX_OSERR, "malloc");
+
+	int error = compress2(deflate, &size, data, dataSize(), Z_BEST_SPEED);
+	if (error != Z_OK) errx(EX_SOFTWARE, "%s: compress2: %d", path, error);
+
+	struct Chunk idat = { .size = size, .type = "IDAT" };
+	writeChunk(idat);
+	writeExpect(deflate, size);
+	writeCrc();
+
+	free(deflate);
+}
+
+static void writeEnd(void) {
+	struct Chunk iend = { .size = 0, .type = "IEND" };
+	writeChunk(iend);
+	writeCrc();
+}
+
+enum PACKED Filter {
+	None,
+	Sub,
+	Up,
+	Average,
+	Paeth,
+	FilterCount,
+};
+
+static struct {
+	bool brokenPaeth;
+	bool filt;
+	bool recon;
+	uint8_t declareFilter;
+	uint8_t applyFilter;
+	enum Filter declareFilters[255];
+	enum Filter applyFilters[255];
+	bool invert;
+	bool mirror;
+	bool zeroX;
+	bool zeroY;
+} options;
+
+struct Bytes {
+	uint8_t x;
+	uint8_t a;
+	uint8_t b;
+	uint8_t c;
+};
+
+static uint8_t paethPredictor(struct Bytes f) {
+	int32_t p = (int32_t)f.a + (int32_t)f.b - (int32_t)f.c;
+	int32_t pa = abs(p - (int32_t)f.a);
+	int32_t pb = abs(p - (int32_t)f.b);
+	int32_t pc = abs(p - (int32_t)f.c);
+	if (pa <= pb && pa <= pc) return f.a;
+	if (options.brokenPaeth) {
+		if (pb < pc) return f.b;
+	} else {
+		if (pb <= pc) return f.b;
+	}
+	return f.c;
+}
+
+static uint8_t recon(enum Filter type, struct Bytes f) {
+	switch (type) {
+		case None:    return f.x;
+		case Sub:     return f.x + f.a;
+		case Up:      return f.x + f.b;
+		case Average: return f.x + ((uint32_t)f.a + (uint32_t)f.b) / 2;
+		case Paeth:   return f.x + paethPredictor(f);
+		default:      abort();
+	}
+}
+
+static uint8_t filt(enum Filter type, struct Bytes f) {
+	switch (type) {
+		case None:    return f.x;
+		case Sub:     return f.x - f.a;
+		case Up:      return f.x - f.b;
+		case Average: return f.x - ((uint32_t)f.a + (uint32_t)f.b) / 2;
+		case Paeth:   return f.x - paethPredictor(f);
+		default:      abort();
+	}
+}
+
+static struct Line {
+	enum Filter type;
+	uint8_t data[];
+} **lines;
+
+static void scanlines(void) {
+	lines = calloc(header.height, sizeof(*lines));
+	if (!lines) err(EX_OSERR, "calloc(%u, %zu)", header.height, sizeof(*lines));
+
+	size_t stride = 1 + lineSize();
+	for (uint32_t y = 0; y < header.height; ++y) {
+		lines[y] = (struct Line *)&data[y * stride];
+		if (lines[y]->type >= FilterCount) {
+			errx(EX_DATAERR, "%s: invalid filter type %hhu", path, lines[y]->type);
+		}
+	}
+}
+
+static struct Bytes origBytes(uint32_t y, size_t i) {
+	bool a = (i >= pixelSize()), b = (y > 0), c = (a && b);
+	return (struct Bytes) {
+		.x = lines[y]->data[i],
+		.a = a ? lines[y]->data[i - pixelSize()] : 0,
+		.b = b ? lines[y - 1]->data[i] : 0,
+		.c = c ? lines[y - 1]->data[i - pixelSize()] : 0,
+	};
+}
+
+static void reconData(void) {
+	for (uint32_t y = 0; y < header.height; ++y) {
+		for (size_t i = 0; i < lineSize(); ++i) {
+			if (options.filt) {
+				lines[y]->data[i] = filt(lines[y]->type, origBytes(y, i));
+			} else {
+				lines[y]->data[i] = recon(lines[y]->type, origBytes(y, i));
+			}
+		}
+		lines[y]->type = None;
+	}
+}
+
+static void filterData(void) {
+	for (uint32_t y = header.height - 1; y < header.height; --y) {
+		uint8_t filter[FilterCount][lineSize()];
+		uint32_t heuristic[FilterCount] = {0};
+		enum Filter minType = None;
+		for (enum Filter type = None; type < FilterCount; ++type) {
+			for (size_t i = 0; i < lineSize(); ++i) {
+				if (options.recon) {
+					filter[type][i] = recon(type, origBytes(y, i));
+				} else {
+					filter[type][i] = filt(type, origBytes(y, i));
+				}
+				heuristic[type] += abs((int8_t)filter[type][i]);
+			}
+			if (heuristic[type] < heuristic[minType]) minType = type;
+		}
+
+		if (options.declareFilter) {
+			lines[y]->type = options.declareFilters[y % options.declareFilter];
+		} else {
+			lines[y]->type = minType;
+		}
+
+		if (options.applyFilter) {
+			enum Filter type = options.applyFilters[y % options.applyFilter];
+			memcpy(lines[y]->data, filter[type], lineSize());
+		} else {
+			memcpy(lines[y]->data, filter[minType], lineSize());
+		}
+	}
+}
+
+static void invert(void) {
+	for (uint32_t y = 0; y < header.height; ++y) {
+		for (size_t i = 0; i < lineSize(); ++i) {
+			lines[y]->data[i] ^= 0xFF;
+		}
+	}
+}
+
+static void mirror(void) {
+	for (uint32_t y = 0; y < header.height; ++y) {
+		for (size_t i = 0, j = lineSize() - 1; i < j; ++i, --j) {
+			uint8_t t = lines[y]->data[i];
+			lines[y]->data[i] = lines[y]->data[j];
+			lines[y]->data[j] = t;
+		}
+	}
+}
+
+static void zeroX(void) {
+	for (uint32_t y = 0; y < header.height; ++y) {
+		memset(lines[y]->data, 0, pixelSize());
+	}
+}
+
+static void zeroY(void) {
+	memset(lines[0]->data, 0, lineSize());
+}
+
+static void glitch(const char *inPath, const char *outPath) {
+	if (inPath) {
+		path = inPath;
+		file = fopen(path, "r");
+		if (!file) err(EX_NOINPUT, "%s", path);
+	} else {
+		path = "(stdin)";
+		file = stdin;
+	}
+
+	readSignature();
+	readHeader();
+	if (header.color == Indexed) readPalette();
+	readData();
+	fclose(file);
+
+	scanlines();
+	reconData();
+	filterData();
+	if (options.invert) invert();
+	if (options.mirror) mirror();
+	if (options.zeroX) zeroX();
+	if (options.zeroY) zeroY();
+	free(lines);
+
+	if (outPath) {
+		path = outPath;
+		file = fopen(path, "w");
+		if (!file) err(EX_CANTCREAT, "%s", path);
+	} else {
+		path = "(stdout)";
+		file = stdout;
+	}
+
+	writeSignature();
+	writeHeader();
+	if (header.color == Indexed) writePalette();
+	writeData();
+	writeEnd();
+	free(data);
+
+	int error = fclose(file);
+	if (error) err(EX_IOERR, "%s", path);
+}
+
+static enum Filter parseFilter(const char *s) {
+	switch (s[0]) {
+		case 'N': case 'n': return None;
+		case 'S': case 's': return Sub;
+		case 'U': case 'u': return Up;
+		case 'A': case 'a': return Average;
+		case 'P': case 'p': return Paeth;
+		default: errx(EX_USAGE, "invalid filter type %s", s);
+	}
+}
+
+static uint8_t parseFilters(enum Filter *filters, const char *s) {
+	uint8_t len = 0;
+	do {
+		filters[len++] = parseFilter(s);
+		s = strchr(s, ',');
+	} while (s++);
+	return len;
+}
+
+int main(int argc, char *argv[]) {
+	bool stdio = false;
+	char *output = NULL;
+
+	int opt;
+	while (0 < (opt = getopt(argc, argv, "a:cd:fimo:prxy"))) {
+		switch (opt) {
+			break; case 'a':
+				options.applyFilter = parseFilters(options.applyFilters, optarg);
+			break; case 'c': stdio = true;
+			break; case 'd':
+				options.declareFilter = parseFilters(options.declareFilters, optarg);
+			break; case 'f': options.filt = true;
+			break; case 'i': options.invert = true;
+			break; case 'm': options.mirror = true;
+			break; case 'o': output = optarg;
+			break; case 'p': options.brokenPaeth = true;
+			break; case 'r': options.recon = true;
+			break; case 'x': options.zeroX = true;
+			break; case 'y': options.zeroY = true;
+			break; default: return EX_USAGE;
+		}
+	}
+
+	if (argc - optind == 1 && (output || stdio)) {
+		glitch(argv[optind], output);
+	} else if (optind < argc) {
+		for (int i = optind; i < argc; ++i) {
+			glitch(argv[i], argv[i]);
+		}
+	} else {
+		glitch(NULL, output);
+	}
+
+	return EX_OK;
+}