1 #include "gifenc.h"
2
3 #include <stdio.h>
4 #include <stdlib.h>
5 #include <string.h>
6 #include <sys/types.h>
7 #include <sys/stat.h>
8 #include <fcntl.h>
9 #ifdef _WIN32
10 #include <io.h>
11 #else
12 #include <unistd.h>
13 #endif
14
15 /* helper to write a little-endian 16-bit number portably */
16 #define write_num(fd, n) write((fd), (uint8_t []) {(n) & 0xFF, (n) >> 8}, 2)
17
18 static uint8_t vga[0x30] = {
19 0x00, 0x00, 0x00,
20 0xAA, 0x00, 0x00,
21 0x00, 0xAA, 0x00,
22 0xAA, 0x55, 0x00,
23 0x00, 0x00, 0xAA,
24 0xAA, 0x00, 0xAA,
25 0x00, 0xAA, 0xAA,
26 0xAA, 0xAA, 0xAA,
27 0x55, 0x55, 0x55,
28 0xFF, 0x55, 0x55,
29 0x55, 0xFF, 0x55,
30 0xFF, 0xFF, 0x55,
31 0x55, 0x55, 0xFF,
32 0xFF, 0x55, 0xFF,
33 0x55, 0xFF, 0xFF,
34 0xFF, 0xFF, 0xFF,
35 };
36
37 struct Node {
38 uint16_t key;
39 struct Node *children[];
40 };
41 typedef struct Node Node;
42
43 static Node *
new_node(uint16_t key,int degree)44 new_node(uint16_t key, int degree)
45 {
46 Node *node = calloc(1, sizeof(*node) + degree * sizeof(Node *));
47 if (node)
48 node->key = key;
49 return node;
50 }
51
52 static Node *
new_trie(int degree,int * nkeys)53 new_trie(int degree, int *nkeys)
54 {
55 Node *root = new_node(0, degree);
56 /* Create nodes for single pixels. */
57 for (*nkeys = 0; *nkeys < degree; (*nkeys)++)
58 root->children[*nkeys] = new_node(*nkeys, degree);
59 *nkeys += 2; /* skip clear code and stop code */
60 return root;
61 }
62
63 static void
del_trie(Node * root,int degree)64 del_trie(Node *root, int degree)
65 {
66 int i;
67 if (!root)
68 return;
69 for (i = 0; i < degree; i++)
70 del_trie(root->children[i], degree);
71 free(root);
72 }
73
74 static void put_loop(ge_GIF *gif, uint16_t loop);
75
76 ge_GIF *
ge_new_gif(const char * fname,uint16_t width,uint16_t height,uint8_t * palette,int depth,int loop)77 ge_new_gif(
78 const char *fname, uint16_t width, uint16_t height,
79 uint8_t *palette, int depth, int loop
80 )
81 {
82 int i, r, g, b, v;
83 ge_GIF *gif = calloc(1, sizeof(*gif) + 2*width*height);
84 if (!gif)
85 goto no_gif;
86 gif->w = width; gif->h = height;
87 gif->depth = depth > 1 ? depth : 2;
88 gif->frame = (uint8_t *) &gif[1];
89 gif->back = &gif->frame[width*height];
90 gif->fd = creat(fname, 0666);
91 if (gif->fd == -1)
92 goto no_fd;
93 #ifdef _WIN32
94 setmode(gif->fd, O_BINARY);
95 #endif
96 write(gif->fd, "GIF89a", 6);
97 write_num(gif->fd, width);
98 write_num(gif->fd, height);
99 write(gif->fd, (uint8_t []) {0xF0 | (depth-1), 0x00, 0x00}, 3);
100 if (palette) {
101 write(gif->fd, palette, 3 << depth);
102 } else if (depth <= 4) {
103 write(gif->fd, vga, 3 << depth);
104 } else {
105 write(gif->fd, vga, sizeof(vga));
106 i = 0x10;
107 for (r = 0; r < 6; r++) {
108 for (g = 0; g < 6; g++) {
109 for (b = 0; b < 6; b++) {
110 write(gif->fd, (uint8_t []) {r*51, g*51, b*51}, 3);
111 if (++i == 1 << depth)
112 goto done_gct;
113 }
114 }
115 }
116 for (i = 1; i <= 24; i++) {
117 v = i * 0xFF / 25;
118 write(gif->fd, (uint8_t []) {v, v, v}, 3);
119 }
120 }
121 done_gct:
122 if (loop >= 0 && loop <= 0xFFFF)
123 put_loop(gif, (uint16_t) loop);
124 return gif;
125 no_fd:
126 free(gif);
127 no_gif:
128 return NULL;
129 }
130
131 static void
put_loop(ge_GIF * gif,uint16_t loop)132 put_loop(ge_GIF *gif, uint16_t loop)
133 {
134 write(gif->fd, (uint8_t []) {'!', 0xFF, 0x0B}, 3);
135 write(gif->fd, "NETSCAPE2.0", 11);
136 write(gif->fd, (uint8_t []) {0x03, 0x01}, 2);
137 write_num(gif->fd, loop);
138 write(gif->fd, "\0", 1);
139 }
140
141 /* Add packed key to buffer, updating offset and partial.
142 * gif->offset holds position to put next *bit*
143 * gif->partial holds bits to include in next byte */
144 static void
put_key(ge_GIF * gif,uint16_t key,int key_size)145 put_key(ge_GIF *gif, uint16_t key, int key_size)
146 {
147 int byte_offset, bit_offset, bits_to_write;
148 byte_offset = gif->offset / 8;
149 bit_offset = gif->offset % 8;
150 gif->partial |= ((uint32_t) key) << bit_offset;
151 bits_to_write = bit_offset + key_size;
152 while (bits_to_write >= 8) {
153 gif->buffer[byte_offset++] = gif->partial & 0xFF;
154 if (byte_offset == 0xFF) {
155 write(gif->fd, "\xFF", 1);
156 write(gif->fd, gif->buffer, 0xFF);
157 byte_offset = 0;
158 }
159 gif->partial >>= 8;
160 bits_to_write -= 8;
161 }
162 gif->offset = (gif->offset + key_size) % (0xFF * 8);
163 }
164
165 static void
end_key(ge_GIF * gif)166 end_key(ge_GIF *gif)
167 {
168 int byte_offset;
169 byte_offset = gif->offset / 8;
170 if (gif->offset % 8)
171 gif->buffer[byte_offset++] = gif->partial & 0xFF;
172 write(gif->fd, (uint8_t []) {byte_offset}, 1);
173 write(gif->fd, gif->buffer, byte_offset);
174 write(gif->fd, "\0", 1);
175 gif->offset = gif->partial = 0;
176 }
177
178 static void
put_image(ge_GIF * gif,uint16_t w,uint16_t h,uint16_t x,uint16_t y)179 put_image(ge_GIF *gif, uint16_t w, uint16_t h, uint16_t x, uint16_t y)
180 {
181 int nkeys, key_size, i, j;
182 Node *node, *child, *root;
183 int degree = 1 << gif->depth;
184
185 write(gif->fd, ",", 1);
186 write_num(gif->fd, x);
187 write_num(gif->fd, y);
188 write_num(gif->fd, w);
189 write_num(gif->fd, h);
190 write(gif->fd, (uint8_t []) {0x00, gif->depth}, 2);
191 root = node = new_trie(degree, &nkeys);
192 key_size = gif->depth + 1;
193 put_key(gif, degree, key_size); /* clear code */
194 for (i = y; i < y+h; i++) {
195 for (j = x; j < x+w; j++) {
196 uint8_t pixel = gif->frame[i*gif->w+j] & (degree - 1);
197 child = node->children[pixel];
198 if (child) {
199 node = child;
200 } else {
201 put_key(gif, node->key, key_size);
202 if (nkeys < 0x1000) {
203 if (nkeys == (1 << key_size))
204 key_size++;
205 node->children[pixel] = new_node(nkeys++, degree);
206 } else {
207 put_key(gif, degree, key_size); /* clear code */
208 del_trie(root, degree);
209 root = node = new_trie(degree, &nkeys);
210 key_size = gif->depth + 1;
211 }
212 node = root->children[pixel];
213 }
214 }
215 }
216 put_key(gif, node->key, key_size);
217 put_key(gif, degree + 1, key_size); /* stop code */
218 end_key(gif);
219 del_trie(root, degree);
220 }
221
222 static int
get_bbox(ge_GIF * gif,uint16_t * w,uint16_t * h,uint16_t * x,uint16_t * y)223 get_bbox(ge_GIF *gif, uint16_t *w, uint16_t *h, uint16_t *x, uint16_t *y)
224 {
225 int i, j, k;
226 int left, right, top, bottom;
227 left = gif->w; right = 0;
228 top = gif->h; bottom = 0;
229 k = 0;
230 for (i = 0; i < gif->h; i++) {
231 for (j = 0; j < gif->w; j++, k++) {
232 if (gif->frame[k] != gif->back[k]) {
233 if (j < left) left = j;
234 if (j > right) right = j;
235 if (i < top) top = i;
236 if (i > bottom) bottom = i;
237 }
238 }
239 }
240 if (left != gif->w && top != gif->h) {
241 *x = left; *y = top;
242 *w = right - left + 1;
243 *h = bottom - top + 1;
244 return 1;
245 } else {
246 return 0;
247 }
248 }
249
250 /* (From the docs)
251 * The `delay` parameter specifies how long the frame will be shown, in hundreths
252 * of a second. For example, `delay` == 100 means "show this frame for one second"
253 * and `delay` == 25 means "show this frame for a quarter of a second". Note that
254 * short delays may not be supported by some GIF viewers: it's recommended to keep
255 * a minimum of `delay` == 6. If `delay` == 0, no delay information will be stored
256 * for the frame. This can be used when creating still (single-frame) GIF images.
257 */
258 static void
set_delay(ge_GIF * gif,uint16_t d)259 set_delay(ge_GIF *gif, uint16_t d)
260 {
261 write(gif->fd, (uint8_t []) {'!', 0xF9, 0x04, 0x04}, 4);
262 write_num(gif->fd, d);
263 write(gif->fd, "\0\0", 2);
264 }
265
266 void
ge_add_frame(ge_GIF * gif,uint16_t delay)267 ge_add_frame(ge_GIF *gif, uint16_t delay)
268 {
269 uint16_t w, h, x, y;
270 uint8_t *tmp;
271
272 if (delay)
273 set_delay(gif, delay);
274 if (gif->nframes == 0) {
275 w = gif->w;
276 h = gif->h;
277 x = y = 0;
278 } else if (!get_bbox(gif, &w, &h, &x, &y)) {
279 /* image's not changed; save one pixel just to add delay */
280 w = h = 1;
281 x = y = 0;
282 }
283 put_image(gif, w, h, x, y);
284 gif->nframes++;
285 tmp = gif->back;
286 gif->back = gif->frame;
287 gif->frame = tmp;
288 }
289
290 void
ge_close_gif(ge_GIF * gif)291 ge_close_gif(ge_GIF* gif)
292 {
293 write(gif->fd, ";", 1);
294 close(gif->fd);
295 free(gif);
296 }
297