/lib/gifdec/gifdec.c
C | 530 lines | 447 code | 42 blank | 41 comment | 87 complexity | 7a5c87fe9025088d0cc4131cf20097c8 MD5 | raw file
- #include "gifdec.h"
- #include <stdio.h>
- #include <stdlib.h>
- #include <string.h>
- #include <sys/types.h>
- #include <sys/stat.h>
- #include <fcntl.h>
- #ifdef _WIN32
- #include <io.h>
- #else
- #include <unistd.h>
- #endif
- #define MIN(A, B) ((A) < (B) ? (A) : (B))
- #define MAX(A, B) ((A) > (B) ? (A) : (B))
- typedef struct Entry {
- uint16_t length;
- uint16_t prefix;
- uint8_t suffix;
- } Entry;
- typedef struct Table {
- int bulk;
- int nentries;
- Entry *entries;
- } Table;
- static uint16_t
- read_num(int fd)
- {
- uint8_t bytes[2];
- read(fd, bytes, 2);
- return bytes[0] + (((uint16_t) bytes[1]) << 8);
- }
- gd_GIF *
- gd_open_gif(const char *fname)
- {
- int fd;
- uint8_t sigver[3];
- uint16_t width, height, depth;
- uint8_t fdsz, bgidx, aspect;
- int i;
- uint8_t *bgcolor;
- int gct_sz;
- gd_GIF *gif;
- fd = open(fname, O_RDONLY);
- if (fd == -1) return NULL;
- #ifdef _WIN32
- setmode(fd, O_BINARY);
- #endif
- /* Header */
- read(fd, sigver, 3);
- if (memcmp(sigver, "GIF", 3) != 0) {
- fprintf(stderr, "invalid signature\n");
- goto fail;
- }
- /* Version */
- read(fd, sigver, 3);
- if (memcmp(sigver, "89a", 3) != 0) {
- fprintf(stderr, "invalid version\n");
- goto fail;
- }
- /* Width x Height */
- width = read_num(fd);
- height = read_num(fd);
- /* FDSZ */
- read(fd, &fdsz, 1);
- /* Presence of GCT */
- if (!(fdsz & 0x80)) {
- fprintf(stderr, "no global color table\n");
- goto fail;
- }
- /* Color Space's Depth */
- depth = ((fdsz >> 4) & 7) + 1;
- /* Ignore Sort Flag. */
- /* GCT Size */
- gct_sz = 1 << ((fdsz & 0x07) + 1);
- /* Background Color Index */
- read(fd, &bgidx, 1);
- /* Aspect Ratio */
- read(fd, &aspect, 1);
- /* Create gd_GIF Structure. */
- gif = calloc(1, sizeof(*gif));
- if (!gif) goto fail;
- gif->fd = fd;
- gif->width = width;
- gif->height = height;
- gif->depth = depth;
- /* Read GCT */
- gif->gct.size = gct_sz;
- read(fd, gif->gct.colors, 3 * gif->gct.size);
- gif->palette = &gif->gct;
- gif->bgindex = bgidx;
- gif->frame = calloc(4, width * height);
- if (!gif->frame) {
- free(gif);
- goto fail;
- }
- gif->canvas = &gif->frame[width * height];
- if (gif->bgindex)
- memset(gif->frame, gif->bgindex, gif->width * gif->height);
- bgcolor = &gif->palette->colors[gif->bgindex*3];
- if (bgcolor[0] || bgcolor[1] || bgcolor [2])
- for (i = 0; i < gif->width * gif->height; i++)
- memcpy(&gif->canvas[i*3], bgcolor, 3);
- gif->anim_start = lseek(fd, 0, SEEK_CUR);
- goto ok;
- fail:
- close(fd);
- return 0;
- ok:
- return gif;
- }
- static void
- discard_sub_blocks(gd_GIF *gif)
- {
- uint8_t size;
- do {
- read(gif->fd, &size, 1);
- lseek(gif->fd, size, SEEK_CUR);
- } while (size);
- }
- static void
- read_plain_text_ext(gd_GIF *gif)
- {
- if (gif->plain_text) {
- uint16_t tx, ty, tw, th;
- uint8_t cw, ch, fg, bg;
- off_t sub_block;
- lseek(gif->fd, 1, SEEK_CUR); /* block size = 12 */
- tx = read_num(gif->fd);
- ty = read_num(gif->fd);
- tw = read_num(gif->fd);
- th = read_num(gif->fd);
- read(gif->fd, &cw, 1);
- read(gif->fd, &ch, 1);
- read(gif->fd, &fg, 1);
- read(gif->fd, &bg, 1);
- sub_block = lseek(gif->fd, 0, SEEK_CUR);
- gif->plain_text(gif, tx, ty, tw, th, cw, ch, fg, bg);
- lseek(gif->fd, sub_block, SEEK_SET);
- } else {
- /* Discard plain text metadata. */
- lseek(gif->fd, 13, SEEK_CUR);
- }
- /* Discard plain text sub-blocks. */
- discard_sub_blocks(gif);
- }
- static void
- read_graphic_control_ext(gd_GIF *gif)
- {
- uint8_t rdit;
- /* Discard block size (always 0x04). */
- lseek(gif->fd, 1, SEEK_CUR);
- read(gif->fd, &rdit, 1);
- gif->gce.disposal = (rdit >> 2) & 3;
- gif->gce.input = rdit & 2;
- gif->gce.transparency = rdit & 1;
- gif->gce.delay = read_num(gif->fd);
- read(gif->fd, &gif->gce.tindex, 1);
- /* Skip block terminator. */
- lseek(gif->fd, 1, SEEK_CUR);
- }
- static void
- read_comment_ext(gd_GIF *gif)
- {
- if (gif->comment) {
- off_t sub_block = lseek(gif->fd, 0, SEEK_CUR);
- gif->comment(gif);
- lseek(gif->fd, sub_block, SEEK_SET);
- }
- /* Discard comment sub-blocks. */
- discard_sub_blocks(gif);
- }
- static void
- read_application_ext(gd_GIF *gif)
- {
- char app_id[8];
- char app_auth_code[3];
- /* Discard block size (always 0x0B). */
- lseek(gif->fd, 1, SEEK_CUR);
- /* Application Identifier. */
- read(gif->fd, app_id, 8);
- /* Application Authentication Code. */
- read(gif->fd, app_auth_code, 3);
- if (!strncmp(app_id, "NETSCAPE", sizeof(app_id))) {
- /* Discard block size (0x03) and constant byte (0x01). */
- lseek(gif->fd, 2, SEEK_CUR);
- gif->loop_count = read_num(gif->fd);
- /* Skip block terminator. */
- lseek(gif->fd, 1, SEEK_CUR);
- } else if (gif->application) {
- off_t sub_block = lseek(gif->fd, 0, SEEK_CUR);
- gif->application(gif, app_id, app_auth_code);
- lseek(gif->fd, sub_block, SEEK_SET);
- discard_sub_blocks(gif);
- } else {
- discard_sub_blocks(gif);
- }
- }
- static void
- read_ext(gd_GIF *gif)
- {
- uint8_t label;
- read(gif->fd, &label, 1);
- switch (label) {
- case 0x01:
- read_plain_text_ext(gif);
- break;
- case 0xF9:
- read_graphic_control_ext(gif);
- break;
- case 0xFE:
- read_comment_ext(gif);
- break;
- case 0xFF:
- read_application_ext(gif);
- break;
- default:
- fprintf(stderr, "unknown extension: %02X\n", label);
- }
- }
- static Table *
- new_table(int key_size)
- {
- int key;
- int init_bulk = MAX(1 << (key_size + 1), 0x100);
- Table *table = malloc(sizeof(*table) + sizeof(Entry) * init_bulk);
- if (table) {
- table->bulk = init_bulk;
- table->nentries = (1 << key_size) + 2;
- table->entries = (Entry *) &table[1];
- for (key = 0; key < (1 << key_size); key++)
- table->entries[key] = (Entry) {1, 0xFFF, key};
- }
- return table;
- }
- /* Add table entry. Return value:
- * 0 on success
- * +1 if key size must be incremented after this addition
- * -1 if could not realloc table */
- static int
- add_entry(Table **tablep, uint16_t length, uint16_t prefix, uint8_t suffix)
- {
- Table *table = *tablep;
- if (table->nentries == table->bulk) {
- table->bulk *= 2;
- table = realloc(table, sizeof(*table) + sizeof(Entry) * table->bulk);
- if (!table) return -1;
- table->entries = (Entry *) &table[1];
- *tablep = table;
- }
- table->entries[table->nentries] = (Entry) {length, prefix, suffix};
- table->nentries++;
- if ((table->nentries & (table->nentries - 1)) == 0)
- return 1;
- return 0;
- }
- static uint16_t
- get_key(gd_GIF *gif, int key_size, uint8_t *sub_len, uint8_t *shift, uint8_t *byte)
- {
- int bits_read;
- int rpad;
- int frag_size;
- uint16_t key;
- key = 0;
- for (bits_read = 0; bits_read < key_size; bits_read += frag_size) {
- rpad = (*shift + bits_read) % 8;
- if (rpad == 0) {
- /* Update byte. */
- if (*sub_len == 0) {
- read(gif->fd, sub_len, 1); /* Must be nonzero! */
- if (*sub_len == 0)
- return 0x1000;
- }
- read(gif->fd, byte, 1);
- (*sub_len)--;
- }
- frag_size = MIN(key_size - bits_read, 8 - rpad);
- key |= ((uint16_t) ((*byte) >> rpad)) << bits_read;
- }
- /* Clear extra bits to the left. */
- key &= (1 << key_size) - 1;
- *shift = (*shift + key_size) % 8;
- return key;
- }
- /* Compute output index of y-th input line, in frame of height h. */
- static int
- interlaced_line_index(int h, int y)
- {
- int p; /* number of lines in current pass */
- p = (h - 1) / 8 + 1;
- if (y < p) /* pass 1 */
- return y * 8;
- y -= p;
- p = (h - 5) / 8 + 1;
- if (y < p) /* pass 2 */
- return y * 8 + 4;
- y -= p;
- p = (h - 3) / 4 + 1;
- if (y < p) /* pass 3 */
- return y * 4 + 2;
- y -= p;
- /* pass 4 */
- return y * 2 + 1;
- }
- /* Decompress image pixels.
- * Return 0 on success or -1 on out-of-memory (w.r.t. LZW code table). */
- static int
- read_image_data(gd_GIF *gif, int interlace)
- {
- uint8_t sub_len, shift, byte;
- int init_key_size, key_size, table_is_full;
- int frm_off, frm_size, str_len, i, p, x, y;
- uint16_t key, clear, stop;
- int ret;
- Table *table;
- Entry entry;
- off_t start, end;
- read(gif->fd, &byte, 1);
- key_size = (int) byte;
- if (key_size < 2 || key_size > 8)
- return -1;
-
- start = lseek(gif->fd, 0, SEEK_CUR);
- discard_sub_blocks(gif);
- end = lseek(gif->fd, 0, SEEK_CUR);
- lseek(gif->fd, start, SEEK_SET);
- clear = 1 << key_size;
- stop = clear + 1;
- table = new_table(key_size);
- key_size++;
- init_key_size = key_size;
- sub_len = shift = 0;
- key = get_key(gif, key_size, &sub_len, &shift, &byte); /* clear code */
- frm_off = 0;
- ret = 0;
- frm_size = gif->fw*gif->fh;
- while (frm_off < frm_size) {
- if (key == clear) {
- key_size = init_key_size;
- table->nentries = (1 << (key_size - 1)) + 2;
- table_is_full = 0;
- } else if (!table_is_full) {
- ret = add_entry(&table, str_len + 1, key, entry.suffix);
- if (ret == -1) {
- free(table);
- return -1;
- }
- if (table->nentries == 0x1000) {
- ret = 0;
- table_is_full = 1;
- }
- }
- key = get_key(gif, key_size, &sub_len, &shift, &byte);
- if (key == clear) continue;
- if (key == stop || key == 0x1000) break;
- if (ret == 1) key_size++;
- entry = table->entries[key];
- str_len = entry.length;
- for (i = 0; i < str_len; i++) {
- p = frm_off + entry.length - 1;
- x = p % gif->fw;
- y = p / gif->fw;
- if (interlace)
- y = interlaced_line_index((int) gif->fh, y);
- gif->frame[(gif->fy + y) * gif->width + gif->fx + x] = entry.suffix;
- if (entry.prefix == 0xFFF)
- break;
- else
- entry = table->entries[entry.prefix];
- }
- frm_off += str_len;
- if (key < table->nentries - 1 && !table_is_full)
- table->entries[table->nentries - 1].suffix = entry.suffix;
- }
- free(table);
- if (key == stop)
- read(gif->fd, &sub_len, 1); /* Must be zero! */
- lseek(gif->fd, end, SEEK_SET);
- return 0;
- }
- /* Read image.
- * Return 0 on success or -1 on out-of-memory (w.r.t. LZW code table). */
- static int
- read_image(gd_GIF *gif)
- {
- uint8_t fisrz;
- int interlace;
- /* Image Descriptor. */
- gif->fx = read_num(gif->fd);
- gif->fy = read_num(gif->fd);
-
- if (gif->fx >= gif->width || gif->fy >= gif->height)
- return -1;
-
- gif->fw = read_num(gif->fd);
- gif->fh = read_num(gif->fd);
-
- gif->fw = MIN(gif->fw, gif->width - gif->fx);
- gif->fh = MIN(gif->fh, gif->height - gif->fy);
-
- read(gif->fd, &fisrz, 1);
- interlace = fisrz & 0x40;
- /* Ignore Sort Flag. */
- /* Local Color Table? */
- if (fisrz & 0x80) {
- /* Read LCT */
- gif->lct.size = 1 << ((fisrz & 0x07) + 1);
- read(gif->fd, gif->lct.colors, 3 * gif->lct.size);
- gif->palette = &gif->lct;
- } else
- gif->palette = &gif->gct;
- /* Image Data. */
- return read_image_data(gif, interlace);
- }
- static void
- render_frame_rect(gd_GIF *gif, uint8_t *buffer)
- {
- int i, j, k;
- uint8_t index, *color;
- i = gif->fy * gif->width + gif->fx;
- for (j = 0; j < gif->fh; j++) {
- for (k = 0; k < gif->fw; k++) {
- index = gif->frame[(gif->fy + j) * gif->width + gif->fx + k];
- color = &gif->palette->colors[index*3];
- if (!gif->gce.transparency || index != gif->gce.tindex)
- memcpy(&buffer[(i+k)*3], color, 3);
- }
- i += gif->width;
- }
- }
- static void
- dispose(gd_GIF *gif)
- {
- int i, j, k;
- uint8_t *bgcolor;
- switch (gif->gce.disposal) {
- case 2: /* Restore to background color. */
- bgcolor = &gif->palette->colors[gif->bgindex*3];
- i = gif->fy * gif->width + gif->fx;
- for (j = 0; j < gif->fh; j++) {
- for (k = 0; k < gif->fw; k++)
- memcpy(&gif->canvas[(i+k)*3], bgcolor, 3);
- i += gif->width;
- }
- break;
- case 3: /* Restore to previous, i.e., don't update canvas.*/
- break;
- default:
- /* Add frame non-transparent pixels to canvas. */
- render_frame_rect(gif, gif->canvas);
- }
- }
- /* Return 1 if got a frame; 0 if got GIF trailer; -1 if error. */
- int
- gd_get_frame(gd_GIF *gif)
- {
- char sep;
- dispose(gif);
- read(gif->fd, &sep, 1);
- while (sep != ',') {
- if (sep == ';')
- return 0;
- if (sep == '!')
- read_ext(gif);
- else return -1;
- read(gif->fd, &sep, 1);
- }
- if (read_image(gif) == -1)
- return -1;
- return 1;
- }
- void
- gd_render_frame(gd_GIF *gif, uint8_t *buffer)
- {
- memcpy(buffer, gif->canvas, gif->width * gif->height * 3);
- render_frame_rect(gif, buffer);
- }
- int
- gd_is_bgcolor(gd_GIF *gif, uint8_t color[3])
- {
- return !memcmp(&gif->palette->colors[gif->bgindex*3], color, 3);
- }
- void
- gd_rewind(gd_GIF *gif)
- {
- lseek(gif->fd, gif->anim_start, SEEK_SET);
- }
- void
- gd_close_gif(gd_GIF *gif)
- {
- close(gif->fd);
- free(gif->frame);
- free(gif);
- }