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Add PNG get info function

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This commit is contained in:
Adrian Johnson 2008-11-23 22:27:49 +10:30
parent 1892907e24
commit f59a3e03fc
2 changed files with 45 additions and 6 deletions
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5
src/cairo-image-info-private.h
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@ -55,4 +55,9 @@ _cairo_image_info_get_jpx_info (cairo_image_info_t *info,
const unsigned char *data,
long length);
cairo_private cairo_int_status_t
_cairo_image_info_get_png_info (cairo_image_info_t *info,
const unsigned char *data,
long length);
#endif /* CAIRO_IMAGE_INFO_PRIVATE_H */

46
src/cairo-image-info.c
View file

@ -36,6 +36,12 @@
#include "cairoint.h"
#include "cairo-image-info-private.h"
static uint32_t
_get_be32 (const unsigned char *p)
{
return p[0] << 24 | p[1] << 16 | p[2] << 8 | p[3];
}
/* Markers with no parameters. All other markers are followed by a two
* byte length of the parameters. */
#define TEM 0x01
@ -148,12 +154,6 @@ static const unsigned char _jpx_signature[] = {
0x00, 0x00, 0x00, 0x0c, 0x6a, 0x50, 0x20, 0x20, 0x0d, 0x0a, 0x87, 0x0a
};
static uint32_t
_get_be32 (const unsigned char *p)
{
return p[0] << 24 | p[1] << 16 | p[2] << 8 | p[3];
}
static const unsigned char *
_jpx_next_box (const unsigned char *p)
{
@ -239,3 +239,37 @@ _cairo_image_info_get_jpx_info (cairo_image_info_t *info,
return CAIRO_STATUS_SUCCESS;
}
#define PNG_IHDR 0x49484452
static const unsigned char _png_magic[8] = { 137, 80, 78, 71, 13, 10, 26, 10 };
cairo_int_status_t
_cairo_image_info_get_png_info (cairo_image_info_t *info,
const unsigned char *data,
long length)
{
const unsigned char *p = data;
const unsigned char *end = data + length;
if (length < 8 || memcmp (data, _png_magic, 8) != 0)
return CAIRO_INT_STATUS_UNSUPPORTED;
p += 8;
/* The first chunk must be IDHR. IDHR has 13 bytes of data plus
* the 12 bytes of overhead for the chunk. */
if (p + 13 + 12 > end)
return CAIRO_INT_STATUS_UNSUPPORTED;
p += 4;
if (_get_be32 (p) != PNG_IHDR)
return CAIRO_INT_STATUS_UNSUPPORTED;
p += 4;
info->width = _get_be32 (p);
p += 4;
info->height = _get_be32 (p);
return CAIRO_STATUS_SUCCESS;
}