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sngc.c
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sngc.c
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/*****************************************************************************
NAME
sngc.c -- compile SNG to PNG.
*****************************************************************************/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <ctype.h>
#include "png.h"
#include "sng.h"
extern int verbose;
typedef int bool;
#define FALSE 0
#define TRUE 1
#define NONE -2
typedef struct {
char *name; /* name of chunk type */
bool multiple_ok; /* OK to have more than one? */
int count; /* how many have we seen? */
} chunkprops;
#ifndef PNG_KEYWORD_MAX_LENGTH
#define PNG_KEYWORD_MAX_LENGTH 79
#endif /* PNG_KEYWORD_MAX_LENGTH */
#define MEMORY_QUANTUM 1024
#define MAX_PARAMS 16
#define PNG_MAX_LONG 2147483647L /* 2^31 */
/* chunk types */
static chunkprops properties[] =
{
/*
* The PNG 1.0 chunks, listed in order of the summary table in section 4.3.
* IEND is not listed here because it doesn't have to appear in the file.
*/
#define IHDR 0
{"IHDR", FALSE, 0},
#define PLTE 1
{"PLTE", FALSE, 0},
#define IDAT 2
{"IDAT", TRUE, 0},
#define cHRM 3
{"cHRM", FALSE, 0},
#define gAMA 4
{"gAMA", FALSE, 0},
#define iCCP 5
{"iCCP", FALSE, 0},
#define sBIT 6
{"sBIT", FALSE, 0},
#define sRGB 7
{"sRGB", FALSE, 0},
#define bKGD 8
{"bKGD", FALSE, 0},
#define hIST 9
{"hIST", FALSE, 0},
#define tRNS 10
{"tRNS", FALSE, 0},
#define pHYs 11
{"pHYs", FALSE, 0},
#define sPLT 12
{"sPLT", TRUE, 0},
#define tIME 13
{"tIME", FALSE, 0},
#define iTXt 14
{"iTXt", TRUE, 0},
#define tEXt 15
{"tEXt", TRUE, 0},
#define zTXt 16
{"zTXt", TRUE, 0},
/*
* Special-purpose chunks in PNG Extensions 1.2.0 specification.
*/
#define oFFs 17
{"oFFs", FALSE, 0},
#define pCAL 18
{"pCAL", FALSE, 0},
#define sCAL 19
{"sCAL", FALSE, 0},
#define gIFg 20
{"gIFg", FALSE, 0},
#define gIFt 21
{"gIFt", FALSE, 0},
#define gIFx 22
{"gIFx", FALSE, 0},
#define fRAc 23
{"fRAc", FALSE, 0},
/*
* Image pseudo-chunk
*/
#define IMAGE 24
{"IMAGE", FALSE, 0},
/*
* Private chunks
*/
#define PRIVATE 25
{"private", TRUE, 0},
};
static png_color palette[256];
/*************************************************************************
*
* Color-name handling
*
************************************************************************/
static color_item *cname_hashbuckets[COLOR_HASH_MODULUS];
static int cname_initialized;
static int write_transform_options;
static int hash_by_cname(color_item *cp)
/* hash by color's RGB value */
{
unsigned int h = 0;
char *p;
for (p = cp->name; *p; p++)
h = COLOR_HASH_MODULUS * h + *p;
return(h % COLOR_HASH_MODULUS);
}
static color_item *find_by_cname(char *name)
/* find a character name */
{
color_item sc, *hp;
sc.name = name;
for (hp = cname_hashbuckets[hash_by_cname(&sc)]; hp; hp = hp->next)
if (strcmp(hp->name, name) == 0)
return(hp);
return((color_item *)NULL);
}
/*************************************************************************
*
* Token-parsing code
*
************************************************************************/
static char token_buffer[16384];
static int token_class;
#define STRING_TOKEN 1
#define PUNCT_TOKEN 2
#define WORD_TOKEN 3
static bool pushed;
static void escapes(cp, tp)
/* process standard C-style escape sequences in a string */
const char *cp; /* source string with escapes */
char *tp; /* target buffer for digested string */
{
while (*cp)
{
int cval = 0;
if (*cp == '\\' && strchr("0123456789xX", cp[1]))
{
char *dp;
const char *hex = "00112233445566778899aAbBcCdDeEfF";
int dcount = 0;
if (*++cp == 'x' || *cp == 'X')
for (++cp; (dp = strchr(hex, *cp)) && (dcount++ < 2); cp++)
cval = (cval * 16) + (dp - hex) / 2;
else if (*cp == '0')
while (strchr("01234567",*cp) != (char*)NULL && (dcount++ < 3))
cval = (cval * 8) + (*cp++ - '0');
else
while ((strchr("0123456789",*cp)!=(char*)NULL)&&(dcount++ < 3))
cval = (cval * 10) + (*cp++ - '0');
}
else if (*cp == '\\') /* C-style character escapes */
{
switch (*++cp)
{
case '\\': cval = '\\'; break;
case 'n': cval = '\n'; break;
case 't': cval = '\t'; break;
case 'b': cval = '\b'; break;
case 'r': cval = '\r'; break;
default: cval = *cp;
}
cp++;
}
else
cval = *cp++;
*tp++ = cval;
}
*tp = '\0';
}
static int get_token(void)
/* grab a token from yyin */
{
char w, c, *tp = token_buffer;
if (pushed)
{
pushed = FALSE;
if (verbose > 1)
fprintf(stderr, "saved token: %s\n", token_buffer);
return(TRUE);
}
/*
* Skip leading whitespace.
*
* Treat commas, colons, and semicolons as whitespace -- this is
* a mildly sleazy way to ensure that the compiler has
* *really* tolerant syntax...in case we ever decide to change
* this, there are comments reading "comma" at every point
* where we might actually want same.
*/
for (;;)
{
w = fgetc(yyin);
if (w == '\n')
linenum++;
if (feof(yyin))
return(FALSE);
else if (isspace(w) || w == ',' || w == ';' || w == ':')
continue;
else if (w == '#') /* comment */
{
for (;;)
{
w = fgetc(yyin);
if (feof(yyin))
return(FALSE);
if (w == '\n')
{
ungetc(w, yyin);
break;
}
}
}
else /* non-space character */
{
*tp++ = w;
break;
}
}
/* accumulate token */
if (w == '\'' || w == '"')
{
int literal = FALSE;
tp = token_buffer;
for (;;)
{
c = fgetc(yyin);
if (feof(yyin))
return(FALSE);
else if (c == '\\' && !literal)
{
literal = TRUE;
continue;
}
else if (c == w && !literal)
break;
else if (c == '\n' && !literal)
fatal("runaway string");
else if (tp >= token_buffer + sizeof(token_buffer) - 1)
fatal("string token too long");
else
{
if (literal)
{
*tp++ = '\\';
literal = FALSE;
}
*tp++ = c;
}
}
*tp = '\0';
escapes(token_buffer, token_buffer);
token_class = STRING_TOKEN;
}
else if (ispunct(w))
{
*tp = '\0';
token_class = PUNCT_TOKEN;
}
else
{
for (;;)
{
c = fgetc(yyin);
if (feof(yyin))
return(FALSE);
else if (isspace(c))
{
if (c == '\n')
linenum++;
break;
}
else if (ispunct(c) && c != '.')
{
ungetc(c, yyin);
break;
}
else if (tp >= token_buffer + sizeof(token_buffer))
fatal("token too long");
else
*tp++ = c;
}
*tp = '\0';
token_class = WORD_TOKEN;
}
if (verbose > 1)
fprintf(stderr, "token: %s\n", token_buffer);
return(TRUE);
}
static int token_equals(const char *str)
/* does the currently fetched token equal a specified string? */
{
return !strcmp(str, token_buffer);
}
static int get_inner_token(void)
/* get a token within a chunk specification */
{
if (!get_token())
fatal("unexpected EOF");
return(!token_equals("}")); /* do we see end delimiter? */
}
static void push_token(void)
/* push back a token; must always be followed immediately by get_token */
{
if (verbose > 1)
fprintf(stderr, "pushing token: %s\n", token_buffer);
pushed = TRUE;
}
static void require_or_die(const char *str)
/* croak if the next token doesn't match what we expect */
{
if (!get_token())
fatal("unexpected EOF");
else if (!token_equals(str))
fatal("unexpected token `%s' while waiting for %s", token_buffer, str);
}
static png_uint_32 long_numeric(bool token_ok)
/* validate current token as a PNG long (range 0..2^31-1) */
{
unsigned long result;
char *vp;
if (!token_ok)
fatal("EOF while expecting long-integer constant");
result = strtoul(token_buffer, &vp, 0);
if (*vp || result >= PNG_MAX_LONG)
fatal("invalid or out of range long constant `%s'", token_buffer);
return(result);
}
static png_int_32 slong_numeric(bool token_ok)
/* validate current token as a signed PNG long (range 0..2^31-1) */
{
long result;
char *vp;
if (!token_ok)
fatal("EOF while expecting signed long-integer constant");
result = strtol(token_buffer, &vp, 0);
if (*vp || result >= PNG_MAX_LONG || result <= -PNG_MAX_LONG)
fatal("invalid or out of range long constant `%s'", token_buffer);
return(result);
}
static png_uint_16 short_numeric(bool token_ok)
/* validate current token as a PNG long (range 0..2^16-1) */
{
unsigned long result;
char *vp;
if (!token_ok)
fatal("EOF while expecting short-integer constant");
result = strtoul(token_buffer, &vp, 0);
if (*vp || result == 65536)
fatal("invalid or out of range short constant `%s'", token_buffer);
return(result);
}
static png_byte byte_numeric(bool token_ok)
/* validate current token as a byte */
{
unsigned long result;
char *vp;
if (!token_ok)
fatal("EOF while expecting byte constant");
result = strtoul(token_buffer, &vp, 0);
if (*vp || result > 255)
fatal("invalid or out of range byte constant `%s'", token_buffer);
return(result);
}
static double double_numeric(bool token_ok)
/* validate current token as a double-precision value */
{
double result;
char *vp;
if (!token_ok)
fatal("EOF while expecting double-precision constant");
result = strtod(token_buffer, &vp);
if (*vp || result < 0)
fatal("invalid or out of range double-precision constant `%s'", token_buffer);
return(result);
}
static int string_validate(bool token_ok, char *stash)
/* validate current token as a string */
{
if (!token_ok)
fatal("EOF while expecting string constant");
/* else */
{
int len = strlen(token_buffer);
if (len > PNG_STRING_MAX_LENGTH)
fatal("string token is too long");
strncpy(stash, token_buffer, PNG_STRING_MAX_LENGTH);
return(len);
}
}
static int keyword_validate(bool token_ok, char *stash)
/* validate current token as a PNG keyword */
{
if (!token_ok)
fatal("EOF while expecting PNG keyword");
/* else */
{
int len = strlen(token_buffer);
unsigned char *cp;
if (len > PNG_KEYWORD_MAX_LENGTH)
fatal("keyword token is too long");
strncpy(stash, token_buffer, PNG_KEYWORD_MAX_LENGTH);
if (isspace(stash[0]) || isspace(stash[len-1]))
fatal("keywords may not contain leading or trailing spaces");
for (cp = (unsigned char *)stash; *cp; cp++)
if (*cp < 32 || (*cp > 126 && *cp < 161))
fatal("keywords must contain Latin-1 characters only");
else if (isspace(cp[0]) && isspace(cp[1]))
fatal("keywords may not contain consecutive spaces");
return(len);
}
}
static void collect_data(int *pnbytes, png_byte **pbytes)
/* collect data in either bitmap format */
{
/*
* A data segment consists of a byte stream.
* There are presently three formats:
*
* string:
* An ASCII string, doublequote-delimited.
*
* base64:
* One character per byte; values 0-63 are mapped to these characters:
* 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/
*
* Note: This encoding is NOT compatible with RFC2045 base64.
* Indeed, RFC2045 uses this mapping for values 0-63:
* ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/
* There are other differences, e.g. we print no padding character '='.
*
* The advantage of our mapping is that for black and white images,
* we generate only '0' and '1' characters, which result in very
* readable output.
*
* hex:
* Two hex digits per byte.
*
* P1:
* pbm format P1 (see pbm(5)).
*
* P3:
* ppm format P3 (see ppm(5)).
*
* In either format, whitespace is ignored.
*/
png_byte *bytes = xalloc(MEMORY_QUANTUM);
int quanta = 1;
int nbytes = 0;
int ocount = 0;
int c, maxval = 0;
#define BASE64_FMT 0
#define HEX_FMT 1
#define P1_FMT 2
#define P3_FMT 3
int fmt = 0;
if (!get_inner_token())
fatal("missing format type in data segment");
else if (token_class == STRING_TOKEN)
{
*pnbytes = 0;
*pbytes = NULL;
do {
int seglen = strlen(token_buffer);
*pbytes = xrealloc(*pbytes, *pnbytes + seglen);
memcpy(*pbytes + *pnbytes, token_buffer, seglen);
*pnbytes += seglen;
} while
(get_inner_token() && token_class == STRING_TOKEN);
push_token();
return;
}
else if (token_equals("base64"))
fmt = BASE64_FMT;
else if (token_equals("hex"))
fmt = HEX_FMT;
else if (token_equals("P1"))
{
int width = short_numeric(get_token());
int height = short_numeric(get_token());
if (width != png_get_image_width(png_ptr, info_ptr) && height != png_get_image_height(png_ptr, info_ptr))
fatal("pbm image dimensions don't mastch IHDR");
fmt = P1_FMT;
}
else if (token_equals("P3"))
{
int width = short_numeric(get_token());
int height = short_numeric(get_token());
maxval = short_numeric(get_token());
if (width != png_get_image_width(png_ptr, info_ptr) && height != png_get_image_height(png_ptr, info_ptr))
fatal("ppm image dimensions don't match IHDR");
fmt = P3_FMT;
}
else
fatal("unknown data format");
while ((c = fgetc(yyin)))
{
if (feof(yyin))
fatal("unexpected EOF in data segment");
else if (c == ';')
break;
else if (c == '}')
{
ungetc('}', yyin);
break;
}
else if (c == '#') /* handle comments */
{
while ((c = fgetc(yyin)))
if (feof(yyin) || c == '\n')
break;
if (c == '\n')
linenum++;
continue;
}
else if (isspace(c)) /* skip whitespace */
{
if (c == '\n')
linenum++;
continue;
}
else
{
unsigned char value = 0;
if (nbytes >= quanta * MEMORY_QUANTUM)
bytes = xrealloc(bytes, MEMORY_QUANTUM * ++quanta);
switch(fmt)
{
case BASE64_FMT:
// NOTE: The mapping below differs from base64, which uses this mapping:
// ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/
if (isdigit(c))
value = c - '0';
else if (isalpha(c) && isupper(c))
value = (c - 'A') + 10;
else if (isalpha(c) && islower(c))
value = (c - 'a') + 36;
else if (c == '+')
value = 62;
else if (c == '/')
value = 63;
else
fatal("bad character %02x in data block", c);
bytes[nbytes++] = value;
break;
case HEX_FMT:
if (!isxdigit(c))
fatal("bad hex character %02x in data block", c);
else if (isdigit(c))
value = c - '0';
else if (isupper(c))
value = (c - 'A') + 10;
else
value = (c - 'a') + 10;
if (ocount++ % 2)
bytes[nbytes++] |= value;
else
bytes[nbytes] = value * 16;
break;
case P1_FMT:
if (c == '0')
bytes[nbytes++] = 0;
else if (c == '1')
bytes[nbytes++] = 1;
else
fatal("bad pbm character %02x in data block", c);
break;
case P3_FMT:
c = short_numeric(get_token());
if (c > maxval)
fatal("channel value out of range in pbm block");
/*
* Channel order in PBM is R, then G, then B, same as PNG;
* so a straight copy in the order we see them will work.
*/
bytes[nbytes++] = c;
break;
}
}
}
#undef BASE64_FMT
#undef HEX_FMT
#undef P1_FMT
#undef P3_FMT
*pnbytes = nbytes;
*pbytes = bytes;
}
/*************************************************************************
*
* The compiler itself
*
************************************************************************/
static void compile_IHDR(void)
/* parse IHDR specification, set corresponding bits in info_ptr */
{
int d = 8;
png_uint_32 width = 0;
png_uint_32 height = 0;
int color_type = PNG_COLOR_TYPE_GRAY;
int interlace_type = PNG_INTERLACE_NONE;
/* read IHDR data */
while (get_inner_token())
if (token_equals("height"))
height = long_numeric(get_token());
else if (token_equals("width"))
width = long_numeric(get_token());
else if (token_equals("bitdepth"))
d = byte_numeric(get_token());
else if (token_equals("using"))
continue; /* `uses' is just syntactic sugar */
else if (token_equals("grayscale"))
continue; /* so is grayscale */
else if (token_equals("palette"))
color_type |= PNG_COLOR_MASK_PALETTE;
else if (token_equals("color"))
color_type |= PNG_COLOR_MASK_COLOR;
else if (token_equals("alpha"))
color_type |= PNG_COLOR_MASK_ALPHA;
else if (token_equals("with"))
continue; /* `with' is just syntactic sugar */
else if (token_equals("interlace"))
interlace_type = PNG_INTERLACE_ADAM7;
else
fatal("bad token `%s' in IHDR specification", token_buffer);
/* IHDR sanity checks */
if (!height)
fatal("image height is zero or nonexistent");
else if (!width)
fatal("image width is zero or nonexistent");
else if (d != 1 && d != 2 && d != 4 && d != 8 && d != 16)
fatal("illegal bit depth %d in IHDR", d);
else if (color_type == PNG_COLOR_TYPE_PALETTE)
{
if (d > 8)
fatal("bit depth of paletted images must be 1, 2, 4, or 8");
}
else if ((color_type != PNG_COLOR_TYPE_GRAY) && d!=8 && d!=16)
fatal("bit depth of RGB- and alpha-using images must be 8 or 16");
png_set_IHDR(png_ptr, info_ptr, width, height, d, color_type,
interlace_type, PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
}
static void compile_PLTE(void)
/* parse PLTE specification, set corresponding bits in info_ptr */
{
int ncolors;
initialize_hash(hash_by_cname, cname_hashbuckets, &cname_initialized);
memset(palette, '\0', sizeof(palette));
ncolors = 0;
while (get_inner_token())
{
if (ncolors >= 256)
fatal("too many palette entries in PLTE specification");
if (token_class == STRING_TOKEN)
{
color_item *cp = find_by_cname(token_buffer);
if (!cp)
fatal("unknown color name `%s' in PLTE", token_buffer);
else
{
palette[ncolors].red = cp->r;
palette[ncolors].green = cp->g;
palette[ncolors].blue = cp->b;
ncolors++;
}
}
else if (token_equals("("))
{
palette[ncolors].red = byte_numeric(get_token());
/* comma */
palette[ncolors].green = byte_numeric(get_token());
/* comma */
palette[ncolors].blue = byte_numeric(get_token());
require_or_die(")");
ncolors++;
}
else
fatal("bad token %s in PLTE", token_buffer);
}
/* register the accumulated palette entries into the info structure */
png_set_PLTE(png_ptr, info_ptr, palette, ncolors);
}
static void compile_IDAT(void)
/* parse IDAT specification and emit corresponding bits */
{
int nbits;
png_byte *bits;
#ifdef PNG_INFO_IMAGE_SUPPORTED
png_unknown_chunk chunk;
#endif /* PNG_INFO_IMAGE_SUPPORTED */
/*
* Collect raw hex data and write it out as a chunk.
*/
collect_data(&nbits, &bits);
require_or_die("}");
#ifndef PNG_INFO_IMAGE_SUPPORTED
png_write_chunk(png_ptr, "IDAT", bits, nbits);
free(bits);
#else
memcpy(chunk.name, "IDAT", sizeof(chunk.name));
chunk.data = bits;
chunk.size = nbits;
png_set_unknown_chunks(png_ptr, info_ptr, &chunk, 1);
// TODO: also use png_set_unknown_chunk_location if libpng before 1.6.0
png_free(png_ptr, bits);
#endif /* PNG_INFO_IMAGE_SUPPORTED */
}
static void compile_cHRM(void)
/* parse cHRM specification, set corresponding bits in info_ptr */
{
char cmask = 0;
float wx = 0, wy = 0, rx = 0, ry = 0, gx = 0, gy = 0, bx = 0, by = 0;
while (get_inner_token())
{
if (token_equals("white"))
{
require_or_die("(");
wx = double_numeric(get_inner_token());
/* comma */
wy = double_numeric(get_inner_token());
require_or_die(")");
cmask |= 0x01;
}
else if (token_equals("red"))
{
require_or_die("(");
rx = double_numeric(get_inner_token());
/* comma */
ry = double_numeric(get_inner_token());
require_or_die(")");
cmask |= 0x02;
}
else if (token_equals("green"))
{
require_or_die("(");
gx = double_numeric(get_inner_token());
/* comma */
gy = double_numeric(get_inner_token());
require_or_die(")");
cmask |= 0x04;
}
else if (token_equals("blue"))
{
require_or_die("(");
bx = double_numeric(get_inner_token());
/* comma */
by = double_numeric(get_inner_token());
require_or_die(")");
cmask |= 0x08;
}
else
fatal("invalid color `%s' name in cHRM specification",token_buffer);
}
if (cmask != 0x0f)
fatal("cHRM specification is not complete");
else
{
#ifdef PNG_FLOATING_POINT_SUPPORTED
png_set_cHRM(png_ptr, info_ptr,
wx, wy, rx, ry, gx, gy, bx, by);
#else
#ifdef PNG_FIXED_POINT_SUPPORTED
png_set_cHRM_fixed(png_ptr, info_ptr,
FLOAT_TO_FIXED(wx),
FLOAT_TO_FIXED(wy),
FLOAT_TO_FIXED(rx),
FLOAT_TO_FIXED(ry),
FLOAT_TO_FIXED(gx),
FLOAT_TO_FIXED(gy),
FLOAT_TO_FIXED(bx),
FLOAT_TO_FIXED(by));
#endif
#endif
}
}
static void compile_gAMA(void)
/* compile and emit an gAMA chunk */
{
double gamma = double_numeric(get_token());
#ifdef PNG_FLOATING_POINT_SUPPORTED
png_set_gAMA(png_ptr, info_ptr, gamma);
#endif
#ifdef PNG_FIXED_POINT_SUPPORTED
png_set_gAMA_fixed(png_ptr, info_ptr, FLOAT_TO_FIXED(gamma));
#endif
if (!get_token() || !token_equals("}"))
fatal("bad token `%s' in gAMA specification", token_buffer);
}
static void compile_iCCP(void)
/* compile and emit an iCCP chunk */
{
int nname = 0, data_len = 0;
char name[PNG_KEYWORD_MAX_LENGTH+1];
png_byte *data;
while (get_inner_token())
if (token_equals("name"))
nname = keyword_validate(get_token(), name);
else if (token_equals("profile"))
collect_data(&data_len, &data);
if (!nname || !data_len)
fatal("incomplete iCCP specification");
png_set_iCCP(png_ptr, info_ptr, name, PNG_COMPRESSION_TYPE_BASE,
data, data_len);
free(data);
}
static void compile_sBIT(void)
/* compile an sBIT chunk, set corresponding bits in info_ptr */
{
png_color_8 sigbits;
png_byte color_type = png_get_color_type(png_ptr, info_ptr);
png_byte bit_depth = png_get_bit_depth(png_ptr, info_ptr);
bool color = (color_type & (PNG_COLOR_MASK_PALETTE | PNG_COLOR_MASK_COLOR));
int sample_depth = ((color_type & PNG_COLOR_MASK_PALETTE) ? 8 : bit_depth);
while (get_inner_token())
if (token_equals("red"))
{
if (!color)
fatal("No color channels in this image type");
sigbits.red = byte_numeric(get_token());
if (sigbits.red > sample_depth)
fatal("red sample depth out of range");
}
else if (token_equals("green"))
{
if (!color)
fatal("No color channels in this image type");
sigbits.green = byte_numeric(get_token());
if (sigbits.green > sample_depth)
fatal("red sample depth out of range");
}
else if (token_equals("blue"))
{
if (!color)
fatal("No color channels in this image type");
sigbits.blue = byte_numeric(get_token());
if (sigbits.blue > sample_depth)
fatal("red sample depth out of range");
}
else if (token_equals("gray"))
{
if (color)
fatal("No gray channel in this image type");
sigbits.gray = byte_numeric(get_token());
if (sigbits.gray > sample_depth)
fatal("gray sample depth out of range");
}
else if (token_equals("alpha"))
{
if (color_type & PNG_COLOR_MASK_ALPHA)
fatal("No alpha channel in this image type");
sigbits.alpha = byte_numeric(get_token());
if (sigbits.alpha > sample_depth)
fatal("alpha sample depth out of range");
}
else
fatal("invalid channel name `%s' in sBIT specification",
token_buffer);
png_set_sBIT(png_ptr, info_ptr, &sigbits);
}
static void compile_bKGD(void)
/* compile a bKGD chunk, put data in info structure */
{
png_color_16 bkgbits;
png_byte color_type = png_get_color_type(png_ptr, info_ptr);
while (get_inner_token())
if (token_equals("red"))
{
if (!(color_type & PNG_COLOR_MASK_COLOR))
fatal("Can't use color background with this image type");
bkgbits.red = short_numeric(get_token());
}
else if (token_equals("green"))
{
if (!(color_type & PNG_COLOR_MASK_COLOR))
fatal("Can't use color background with this image type");
bkgbits.green = short_numeric(get_token());
}
else if (token_equals("blue"))
{
if (!(color_type & PNG_COLOR_MASK_COLOR))
fatal("Can't use color background with this image type");
bkgbits.blue = short_numeric(get_token());
}
else if (token_equals("gray"))
{
if (color_type & (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE))
fatal("Can't use color background with this image type");
bkgbits.gray = short_numeric(get_token());
}
else if (token_equals("index"))
{
if (!(color_type & PNG_COLOR_MASK_PALETTE))
fatal("Can't use index background with a non-palette image");
bkgbits.index = byte_numeric(get_token());
}
else
fatal("invalid channel `%s' name in bKGD specification",
token_buffer);
png_set_bKGD(png_ptr, info_ptr, &bkgbits);
}