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giftiles.c

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nhmall
2016-03-07 08:40:03 -05:00
parent 4aec98ce9c
commit 40f2994ba7
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/* NetHack 3.6 tileset.h $NHDT-Date: 1457207052 2016/03/05 19:44:12 $ $NHDT-Branch: chasonr $:$NHDT-Revision: 1.0 $ */
/* Copyright (c) Ray Chason, 2016. */
/* NetHack may be freely redistributed. See license for details. */
/* giftiles.c -- read a tile map in GIF format */
/* Reference: GIF specification,, retrieved from
* http://www.w3.org/Graphics/GIF/spec-gif89a.txt */
#include "config.h"
#include "tileset.h"
#define MIN_LZW_BITS 3
#define MAX_LZW_BITS 12
#define END_OF_DATA 0x7FFF
/* For use when reading the GIF as a bitstream */
struct Bitstream {
/* The file */
FILE *fp;
/* For unpacking LZW codes */
unsigned long bits;
unsigned char num_bits;
unsigned char bit_width;
unsigned char initial_bit_width;
unsigned char block_size;
/* The dictionary */
struct {
unsigned char byte;
unsigned short next;
} dictionary[1 << MAX_LZW_BITS];
unsigned short dict_size;
/* The string currently being decoded */
unsigned char string[1 << MAX_LZW_BITS];
unsigned short str_size;
unsigned short last_code;
};
struct DataBlock {
size_t size;
size_t index;
unsigned char *data;
};
static boolean FDECL(read_data_block, (struct Bitstream *gif, struct DataBlock *block));
static void FDECL(free_data_block, (struct DataBlock *block));
static unsigned short FDECL(read_u16, (const unsigned char buf[2]));
static void FDECL(init_decoder, (struct Bitstream *gif, unsigned bit_width));
static void FDECL(reset_decoder, (struct Bitstream *gif));
static int FDECL(decode, (struct Bitstream *gif, struct DataBlock *block));
static int FDECL(get_code, (struct Bitstream *gif, struct DataBlock *block));
static unsigned FDECL(interlace_incr, (unsigned y, unsigned height));
/*
* GIF specifies a canvas, which may have a palette (the "global color table")
* of up to 256 colors, of which one is a background color, and zero or more
* images, each of which may have its own palette (a "local color table")
* independently of the canvas. We will join all palettes found into a single
* palette, and indicate that the image uses a palette if, and only if, the
* various palettes do not total more than 256 colors.
*/
boolean
read_gif_tiles(filename, image)
const char *filename;
struct TileSetImage *image;
{
struct Bitstream gif;
struct DataBlock block;
unsigned char buf[1024];
size_t size, num_pixels, i;
/* Image data not returned to the caller */
boolean have_gct; /* global color table is present */
unsigned gct_size; /* global color table size */
unsigned back_color; /* index for background color */
unsigned trans_color = 0xFFFF; /* index for transparent palette entry */
block.data = NULL; /* custodial */
gif.fp = NULL; /* custodial */
image->width = 0;
image->height = 0;
image->pixels = NULL; /* custodial, returned */
image->indexes = NULL; /* custodial, returned */
image->image_desc = NULL; /* custodial, returned */
image->tile_width = 0;
image->tile_height = 0;
gif.fp = fopen(filename, "rb");
if (gif.fp == NULL) goto error;
/* 17. Header */
size = fread(buf, 1, 6, gif.fp);
if (size < 6) goto error;
if (memcmp(buf, "GIF87a", 6) != 0 && memcmp(buf, "GIF89a", 6) != 0)
goto error;
/* 18. Logical screen descriptor */
size = fread(buf, 1, 7, gif.fp);
if (size < 7) goto error;
image->width = read_u16(buf + 0);
image->height = read_u16(buf + 2);
have_gct = (buf[4] & 0x80) != 0;
gct_size = 1 << ((buf[4] & 0x07) + 1);
back_color = buf[5];
if (image->width == 0 || image->height == 0) goto error;
/* 19. Global Color Table */
for (i = 0; i < SIZE(image->palette); ++i) {
image->palette[i].r = 0;
image->palette[i].g = 0;
image->palette[i].b = 0;
image->palette[i].a = 255;
}
if (have_gct) {
size = fread(buf, 3, gct_size, gif.fp);
if (size < gct_size) goto error;
for (i = 0; i < gct_size; ++i) {
image->palette[i].r = buf[i * 3 + 0];
image->palette[i].g = buf[i * 3 + 1];
image->palette[i].b = buf[i * 3 + 2];
image->palette[i].a = 255;
}
}
/* Allocate pixel area; watch out for overflow */
num_pixels = (size_t) image->width * (size_t) image->height;
if (num_pixels / image->width != image->height) goto error; /* overflow */
size = num_pixels * sizeof(image->pixels[0]);
if (size / sizeof(image->pixels[0]) != num_pixels) goto error; /* overflow */
image->pixels = (struct Pixel *) alloc(size);
image->indexes = (unsigned char *) alloc(num_pixels);
/* Fill with the background color */
for (i = 0; i < num_pixels; ++i) {
image->pixels[i] = image->palette[back_color];
image->indexes[i] = back_color;
}
/* Read the image data */
while (TRUE) {
int b = fgetc(gif.fp);
if (b == EOF) goto error;
/* 27. Trailer (0x3B) */
if (b == 0x3B) break;
switch (b) {
case 0x2C:
/* 20. Image descriptor (0x2C) */
{
unsigned img_left, img_top, img_width, img_height;
boolean have_lct, interlace;
unsigned lct_start, lct_size;
struct Pixel lct[256];
int b;
unsigned x, y, x2, y2;
size = fread(buf, 1, 9, gif.fp);
if (size < 9) goto error;
img_left = read_u16(buf + 0);
img_top = read_u16(buf + 2);
img_width = read_u16(buf + 4);
img_height = read_u16(buf + 6);
have_lct = (buf[8] & 0x80) != 0;
interlace = (buf[8] & 0x40) != 0;
lct_size = 1 << ((buf[8] & 0x07) + 1);
/* 21. Local color table */
lct_start = 0;
memcpy(lct, image->palette, sizeof(lct));
if (have_lct) {
size = fread(buf, 3, lct_size, gif.fp);
if (size < lct_size) goto error;
for (i = 0; i < lct_size; ++i) {
lct[i].r = buf[i * 3 + 0];
lct[i].g = buf[i * 3 + 1];
lct[i].b = buf[i * 3 + 2];
lct[i].a = 255;
}
/*
* The combined palette may exceed 256 colors, in which
* case the indexes array will be discarded, indicating a
* full-color image.
*/
if (lct_size + gct_size <= 256) {
memcpy(image->palette, lct, sizeof(lct[0]) * lct_size);
}
lct_start = gct_size;
gct_size += lct_start;
}
if (trans_color != 0xFFFF) {
lct[trans_color].a = 0;
if (!have_lct) {
/* FIXME: this will affect all images using the global
* color table, not just the current one */
image->palette[trans_color].a = 0;
}
}
/* 22. Table based image data */
b = fgetc(gif.fp);
if (b == EOF) goto error;
if (b < MIN_LZW_BITS - 1 || MAX_LZW_BITS - 1 < b) goto error;
init_decoder(&gif, b);
x = 0;
y = 0;
if (!read_data_block(&gif, &block)) goto error;
while (TRUE) {
b = decode(&gif, &block);
if (b == EOF) goto error;
if (b == END_OF_DATA) break;
if (y >= img_height) goto error;
x2 = img_left + x;
y2 = img_top + y;
if (x2 < image->width && y2 < image->height) {
image->pixels[y2 * image->width + x2] = lct[b];
image->indexes[y2 * image->width + x2] = b + lct_start;
}
++x;
if (x >= img_width) {
x = 0;
if (interlace) {
y = interlace_incr(y, img_height);
} else {
++y;
}
}
}
free_data_block(&block);
trans_color = 0xFFFF;
}
break;
case 0x21:
/* Extension blocks */
{
int label;
label = fgetc(gif.fp);
if (label == EOF) goto error;
if (!read_data_block(&gif, &block)) goto error;
switch (label) {
case 0xF9:
/* 23. Graphic control extension (0xF9) */
if (block.size >= 4 && (block.data[0] & 0x01) != 0) {
/* image has a transparent index */
trans_color = block.data[3];
}
break;
#if 0
case 0xFE:
/* 24. Comment extension (0xFE) */
break;
case 0x01:
/* 25. Plain text extension (0x01) */
break;
#endif
case 0xFF:
/* 26. Application extension (0xFF) */
if (block.size > 11
&& memcmp(block.data, "NETHACK3GIF", 11) == 0
&& image->image_desc == NULL) {
memmove(block.data, block.data + 11, block.size - 11);
block.data[block.size - 11] = '\0';
image->image_desc = (char *) block.data;
block.data = NULL;
}
break;
default:
/* Unknown extension type */
break;
}
free_data_block(&block);
}
break;
default:
goto error;
}
}
fclose(gif.fp);
free_data_block(&block);
if (gct_size > 256) {
/* Max palette size exceeded; indexes array is not meaningful */
free(image->indexes);
image->indexes = NULL;
}
return TRUE;
error:
if (gif.fp) fclose(gif.fp);
free_data_block(&block);
free(image->pixels);
image->pixels = NULL;
free(image->indexes);
image->indexes = NULL;
free(image->image_desc);
image->image_desc = NULL;
return FALSE;
}
static void
init_decoder(gif, bit_width)
struct Bitstream *gif;
unsigned bit_width;
{
unsigned i;
unsigned clear;
gif->bits = 0;
gif->num_bits = 0;
gif->initial_bit_width = bit_width;
gif->block_size = 0;
clear = 1 << bit_width;
gif->dict_size = clear + 2;
for (i = 0; i < clear; ++i) {
gif->dictionary[i].byte = i;
gif->dictionary[i].next = 0xFFFF;
}
gif->str_size = 0;
reset_decoder(gif);
}
static void
reset_decoder(gif)
struct Bitstream *gif;
{
/* Set the bit width */
gif->bit_width = gif->initial_bit_width + 1;
/* Reset the dictionary */
gif->dict_size = (1 << gif->initial_bit_width) + 2;
/* No last code */
gif->last_code = 0xFFFF;
}
static int
decode(gif, block)
struct Bitstream *gif;
struct DataBlock *block;
{
int code;
unsigned clear = 1 << gif->initial_bit_width;
/* If a string is being decoded, return the next byte */
if (gif->str_size != 0) {
return gif->string[--gif->str_size];
}
/* Get the next code, until code other than clear */
while (TRUE) {
code = get_code(gif, block);
if (code != clear) break;
reset_decoder(gif);
}
if (code == EOF) return EOF;
if (code == clear + 1) return END_OF_DATA;
if (code > gif->dict_size) return EOF;
/* Add a new string to the dictionary */
if (gif->last_code != 0xFFFF && gif->dict_size < SIZE(gif->dictionary)) {
unsigned next_code;
if (code < gif->dict_size) {
next_code = code;
} else {
next_code = gif->last_code;
}
while (next_code >= clear) {
next_code = gif->dictionary[next_code].next;
}
gif->dictionary[gif->dict_size].next = gif->last_code;
gif->dictionary[gif->dict_size].byte = next_code;
++gif->dict_size;
if (gif->dict_size >= 1 << gif->bit_width
&& gif->bit_width < MAX_LZW_BITS) {
++gif->bit_width;
}
}
gif->last_code = code;
/* code is less than gif->dict_size and not equal to clear or clear + 1 */
/* Prepare the decoded string for return; note that it is stored in
* reverse order */
while (code >= clear) {
gif->string[gif->str_size++] = gif->dictionary[code].byte;
code = gif->dictionary[code].next;
}
return code;
}
static int
get_code(gif, block)
struct Bitstream *gif;
struct DataBlock *block;
{
int code;
while (gif->num_bits < gif->bit_width) {
unsigned char b;
if (block->index >= block->size) return EOF;
b = block->data[block->index++];
gif->bits |= (unsigned long)b << gif->num_bits;
gif->num_bits += 8;
}
code = (int) (gif->bits & ((1UL << gif->bit_width) - 1));
gif->bits >>= gif->bit_width;
gif->num_bits -= gif->bit_width;
return code;
}
static unsigned
interlace_incr(y, height)
unsigned y;
unsigned height;
{
static const unsigned char incr[] = { 8, 2, 4, 2 };
/* The lower three bits indicate the current pass */
/* Advance to the next row of the current pass */
y += incr[y & 0x3];
/* Go to the next pass if y exceeds height */
/* Might not be the immediately following pass if height is small */
if (y >= height && (y & 0x7) == 0) {
/* Pass 1 -> Pass 2 */
y = 4;
}
if (y >= height && (y & 0x7) == 4) {
/* Pass 2 -> Pass 3 */
y = 2;
}
if (y >= height && (y & 0x3) == 2) {
/* Pass 3 -> Pass 4 */
y = 1;
}
return y;
}
/* Decode an unsigned 16 bit quantity */
static unsigned short
read_u16(buf)
const unsigned char buf[2];
{
return ((unsigned short)buf[0] << 0)
| ((unsigned short)buf[1] << 8);
}
static boolean
read_data_block(gif, block)
struct Bitstream *gif;
struct DataBlock *block;
{
long pos = ftell(gif->fp);
int b;
size_t i;
free_data_block(block);
/* Get the length of the data block */
while (TRUE) {
b = fgetc(gif->fp);
if (b == EOF) return FALSE;
if (b == 0) break;
block->size += b;
fseek(gif->fp, b, SEEK_CUR);
}
fseek(gif->fp, pos, SEEK_SET);
/* Allocate memory */
block->data = (unsigned char *) alloc(block->size);
/* Read the data from the file */
i = 0;
while (TRUE) {
b = fgetc(gif->fp);
if (b == EOF) return FALSE;
if (b == 0) break;
if (fread(block->data + i, 1, b, gif->fp) != b) return FALSE;
i += b;
}
block->index = 0;
return TRUE;
}
static void
free_data_block(block)
struct DataBlock *block;
{
free(block->data);
block->size = 0;
block->data = NULL;
}