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-rw-r--r--src/load_gif.c384
1 files changed, 384 insertions, 0 deletions
diff --git a/src/load_gif.c b/src/load_gif.c
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+++ b/src/load_gif.c
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+/*
+ * GIF Loader
+ * by Paul Bartrum
+ *
+ * Comment by Eric Stevens (tome@eastevens.com):
+ *
+ * This file has been modified to work with Allegro 4.0.3 that comes with
+ * DJGPP 2.0.3 for the use in compiling for ToME 2.2.7. This modification
+ * changes a variable name to one that is not in conflict with Allegro
+ * variable name. The variable 'empty_string' was changed to 'empty_str'.
+ *
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <allegro.h>
+#include <string.h>
+
+int _color_load_depth(int depth);
+
+struct LZW_STRING
+{
+ short base;
+ char new;
+ short length;
+};
+
+PACKFILE *f;
+int empty_str, curr_bit_size, bit_overflow;
+int bit_pos, data_pos, data_len, entire, code;
+int cc, string_length, i, bit_size;
+unsigned char string[4096];
+struct LZW_STRING str[4096];
+BITMAP *bmp;
+int image_x, image_y, image_w, image_h, x, y;
+int interlace;
+
+
+void clear_table(void)
+{
+ empty_str = cc + 2;
+ curr_bit_size = bit_size + 1;
+ bit_overflow = 0;
+}
+
+
+void get_code(void)
+{
+ if (bit_pos + curr_bit_size > 8)
+ {
+ if (data_pos >= data_len)
+ {
+ data_len = pack_getc(f);
+ data_pos = 0;
+ }
+ entire = (pack_getc(f) << 8) + entire;
+ data_pos ++;
+ }
+ if (bit_pos + curr_bit_size > 16)
+ {
+ if (data_pos >= data_len)
+ {
+ data_len = pack_getc(f);
+ data_pos = 0;
+ }
+ entire = (pack_getc(f) << 16) + entire;
+ data_pos ++;
+ }
+ code = (entire >> bit_pos) & ((1 << curr_bit_size) - 1);
+ if (bit_pos + curr_bit_size > 8)
+ entire >>= 8;
+ if (bit_pos + curr_bit_size > 16)
+ entire >>= 8;
+ bit_pos = (bit_pos + curr_bit_size) % 8;
+ if (bit_pos == 0)
+ {
+ if (data_pos >= data_len)
+ {
+ data_len = pack_getc(f);
+ data_pos = 0;
+ }
+ entire = pack_getc(f);
+ data_pos ++;
+ }
+}
+
+
+void input_string(int num)
+{
+ if (num < cc)
+ {
+ string_length = 1;
+ string[0] = str[num].new;
+ }
+ else
+ {
+ i = str[num].length;
+ string_length = i;
+ while (i > 0)
+ {
+ i --;
+ string[i] = str[num].new;
+ num = str[num].base;
+ }
+ /* if(num != -1) **-{[ERROR]}-** */
+ }
+}
+
+
+void output_string(void)
+{
+ for (i = 0; i < string_length; i ++)
+ {
+ putpixel(bmp, x, y, string[i]);
+ x ++;
+ if (x >= image_x + image_w)
+ {
+ x = image_x;
+ y += interlace;
+ if (interlace)
+ {
+ if (y >= image_y + image_h)
+ {
+ if (interlace == 8 && (y - image_y) % 8 == 0)
+ {
+ interlace = 8;
+ y = image_y + 4;
+ }
+ else if (interlace == 8 && (y - image_y) % 8 == 4)
+ {
+ interlace = 4;
+ y = image_y + 2;
+ }
+ else if (interlace == 4)
+ {
+ interlace = 2;
+ y = image_y + 1;
+ }
+ }
+ }
+ }
+ }
+}
+
+
+/* load_gif:
+ * Loads a 2-256 colour GIF file onto a bitmap, returning the bitmap
+ * structure and storing the pallete data in the specified pallete (this
+ * should be an array of at least 256 RGB structures).
+ */
+BITMAP *load_gif (char *filename, RGB *pal)
+{
+ int width, height, depth;
+ int old;
+ BITMAP *bmp2;
+ int dest_depth;
+
+ f = pack_fopen(filename, F_READ);
+ if (!f) /* can't open file */
+ return NULL;
+
+ i = pack_mgetw(f) << 8;
+ i += pack_getc(f);
+ if (i != 0x474946) /* is it really a GIF? */
+ {
+ pack_fclose(f);
+ return NULL;
+ }
+ pack_fseek(f, 3); /* skip version */
+
+ width = pack_igetw(f);
+ height = pack_igetw(f);
+
+ bmp = create_bitmap_ex(8, width, height);
+ if (bmp == NULL)
+ {
+ pack_fclose(f);
+ return NULL;
+ }
+ clear(bmp);
+
+ i = pack_getc(f);
+ if (i & 128) /* no global colour table? */
+ depth = (i & 7) + 1;
+ else
+ depth = 0;
+
+ pack_fseek(f, 2); /* skip background colour and aspect ratio */
+
+ if (pal && depth) /* only read palette if pal and depth are not 0 */
+ {
+ for (i = 0; i < (1 << depth); i ++)
+ {
+ pal[i].r = pack_getc(f) / 4;
+ pal[i].g = pack_getc(f) / 4;
+ pal[i].b = pack_getc(f) / 4;
+ }
+ }
+ else
+ if (depth)
+ pack_fseek(f, (1 << depth) * 3);
+
+ do
+ {
+ i = pack_getc(f);
+ switch (i)
+ {
+ case 0x2C: /* Image Descriptor */
+ image_x = pack_igetw(f);
+ image_y = pack_igetw(f); /* individual image dimensions */
+ image_w = pack_igetw(f);
+ image_h = pack_igetw(f);
+
+ i = pack_getc(f);
+ if (i & 64)
+ interlace = 8;
+ else
+ interlace = 1;
+
+ if (i & 128)
+ {
+ depth = (i & 7) + 1;
+ if (pal)
+ {
+ for (i = 0; i < (1 << depth); i ++)
+ {
+ pal[i].r = pack_getc(f) / 4;
+ pal[i].g = pack_getc(f) / 4;
+ pal[i].b = pack_getc(f) / 4;
+ }
+ }
+ else
+ pack_fseek(f, (1 << depth) * 3);
+ }
+
+ /* lzw stream starts now */
+ bit_size = pack_getc(f);
+ cc = 1 << bit_size;
+
+ /* initialise string table */
+ for (i = 0; i < cc; i ++)
+ {
+ str[i].base = -1;
+ str[i].new = i;
+ str[i].length = 1;
+ }
+
+ /* initialise the variables */
+ bit_pos = 0;
+ data_len = pack_getc(f);
+ data_pos = 0;
+ entire = pack_getc(f);
+ data_pos ++;
+ string_length = 0;
+ x = image_x;
+ y = image_y;
+
+ /* starting code */
+ clear_table();
+ get_code();
+ if (code == cc)
+ get_code();
+ input_string(code);
+ output_string();
+ old = code;
+
+ while (TRUE)
+ {
+ get_code();
+
+ if (code == cc)
+ {
+ /* starting code */
+ clear_table();
+ get_code();
+ input_string(code);
+ output_string();
+ old = code;
+ }
+ else if (code == cc + 1)
+ {
+ break;
+ }
+ else if (code < empty_str)
+ {
+ input_string(code);
+ output_string();
+
+ if (bit_overflow == 0)
+ {
+ str[empty_str].base = old;
+ str[empty_str].new = string[0];
+ str[empty_str].length = str[old].length + 1;
+ empty_str ++;
+ if (empty_str == (1 << curr_bit_size))
+ curr_bit_size ++;
+ if (curr_bit_size == 13)
+ {
+ curr_bit_size = 12;
+ bit_overflow = 1;
+ }
+ }
+
+ old = code;
+ }
+ else
+ {
+ input_string(old);
+ string[str[old].length] = string[0];
+ string_length ++;
+
+ if (bit_overflow == 0)
+ {
+ str[empty_str].base = old;
+ str[empty_str].new = string[0];
+ str[empty_str].length = str[old].length + 1;
+ empty_str ++;
+ if (empty_str == (1 << curr_bit_size))
+ curr_bit_size ++;
+ if (curr_bit_size == 13)
+ {
+ curr_bit_size = 12;
+ bit_overflow = 1;
+ }
+ }
+
+ output_string();
+ old = code;
+ }
+ }
+ break;
+ case 0x21: /* Extension Introducer */
+ i = pack_getc(f);
+ if (i == 0xF9) /* Graphic Control Extension */
+ {
+ pack_fseek(f, 1); /* skip size (it's 4) */
+ i = pack_getc(f);
+ if (i & 1) /* is transparency enabled? */
+ {
+ pack_fseek(f, 2);
+ pack_getc(f); /* transparent colour */
+ }
+ else
+ pack_fseek(f, 3);
+ }
+ i = pack_getc(f);
+ while (i) /* skip Data Sub-blocks */
+ {
+ pack_fseek(f, i);
+ i = pack_getc(f);
+ }
+ break;
+ case 0x3B: /* Trailer - end of data */
+ pack_fclose(f);
+
+ /* convert to correct colour depth */
+ dest_depth = _color_load_depth(8);
+
+ if (dest_depth != 8)
+ {
+ bmp2 = create_bitmap_ex(dest_depth, bmp->w, bmp->h);
+ if (!bmp2)
+ {
+ destroy_bitmap(bmp);
+ return NULL;
+ }
+
+ select_palette(pal);
+ blit(bmp, bmp2, 0, 0, 0, 0, bmp->w, bmp->h);
+ unselect_palette();
+
+ destroy_bitmap(bmp);
+ bmp = bmp2;
+ }
+
+ return bmp;
+ }
+ }
+ while (TRUE);
+
+ /* this is never executed but DJGPP complains if you leave it out */
+ return NULL;
+}
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