int PNGAPI
pngx_read_image(png_structp png_ptr, png_infop info_ptr,
png_const_charpp fmt_name, png_const_charpp fmt_description)
{
png_byte sig[128];
size_t num;
int (*read_fn)(png_structp, png_infop, FILE *);
FILE *stream;
fpos_t fpos;
int result;
/* Precondition. */
#ifdef PNG_FLAG_MALLOC_NULL_MEM_OK
PNGX_ASSERT_MSG(!(png_ptr->flags & PNG_FLAG_MALLOC_NULL_MEM_OK),
"pngxtern requires a safe allocator");
#endif
/* Read the signature bytes. */
stream = (FILE *)png_get_io_ptr(png_ptr);
PNGX_ASSERT(stream != NULL);
if (fgetpos(stream, &fpos) != 0)
png_error(png_ptr, "Can't ftell in input file stream");
num = fread(sig, 1, sizeof(sig), stream);
if (fsetpos(stream, &fpos) != 0)
png_error(png_ptr, "Can't fseek in input file stream");
/* Try the PNG format first. */
if (pngx_sig_is_png(png_ptr, sig, num, fmt_name, fmt_description) > 0)
{
png_read_png(png_ptr, info_ptr, 0, NULL);
if (getc(stream) != EOF)
{
png_warning(png_ptr, "Extraneous data found after IEND");
fseek(stream, 0, SEEK_END);
}
return 1;
}
/* Check the signature bytes against other known image formats. */
if (pngx_sig_is_bmp(sig, num, fmt_name, fmt_description) > 0)
read_fn = pngx_read_bmp;
else if (pngx_sig_is_gif(sig, num, fmt_name, fmt_description) > 0)
read_fn = pngx_read_gif;
else if (pngx_sig_is_jpeg(sig, num, fmt_name, fmt_description) > 0)
read_fn = pngx_read_jpeg;
else if (pngx_sig_is_pnm(sig, num, fmt_name, fmt_description) > 0)
read_fn = pngx_read_pnm;
else if (pngx_sig_is_tiff(sig, num, fmt_name, fmt_description) > 0)
read_fn = pngx_read_tiff;
else
return 0; /* not a known image format */
/* Read the image. */
result = read_fn(png_ptr, info_ptr, stream);
/* Signature checking may give false positives; reading can still fail. */
if (result <= 0) /* this isn't the format we thought it was */
if (fsetpos(stream, &fpos) != 0)
png_error(png_ptr, "Can't fseek in input file stream");
return result;
}
int /* PRIVATE */
pngx_read_jpeg(png_structp png_ptr, png_infop info_ptr, FILE *stream)
{
png_byte buf[JPEG_SIG_SIZE_MAX];
int sig_code;
if (fread(buf, JPEG_SIG_SIZE_MAX, 1, stream) != 1)
return 0; /* not a JPEG file */
sig_code = pngx_sig_is_jpeg(buf, JPEG_SIG_SIZE_MAX, NULL, NULL);
/* TODO: Use the format names passed by pngx_sig_is_jpeg. */
switch (sig_code)
{
case 1:
png_error(png_ptr, "JPEG decoding is not supported");
/* NOTREACHED */
break;
case 2:
png_error(png_ptr, "JPEG-2000 decoding is not supported");
/* NOTREACHED */
break;
case 3:
png_error(png_ptr, "JNG (JPEG) decoding is not supported");
/* NOTREACHED */
break;
}
if (info_ptr == NULL) /* dummy, keep compilers happy */
return 0;
return 0; /* always fail */
}