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Reenable filter selection (dummy)

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This implements the code for row-by-row filter selection but does not provide an
actual implementation; the selection function just chooses the lowest set filter
bit.

Signed-off-by: John Bowler <jbowler@acm.org>
This commit is contained in:
John Bowler
2016-05-09 13:08:50 -07:00
parent ba356b4e4d
commit 4905ed4aae
5 changed files with 458 additions and 337 deletions
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25
scripts/pnglibconf.dfa
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@@ -935,31 +935,8 @@ option CONVERT_tIME requires WRITE_ANCILLARY_CHUNKS
# the 'first' (lowest numbered) filter will be selected an this typically
# works out as PNG_FILTER_VALUE_NONE.
#
# COMPRESSION_BUFFER_MAX
# WARNING: take care if you set this. This is the maximum amount of input
# data that the implementation of deflate can consume before it outputs a
# Huffman table for that data. I.e. before it commits to an encoding of the
# data it has read. This is used solely to implement a limit on the amount
# of image data buffering that occurs inside libpng before filter selection
# is done. Normally the limit is never reached because of the next setting,
# but this is a compile time limit and it is intended to prevent a potential
# DNS service as a result of an application setting the libpng equivalent of
# volume level 11 (read the wikipedia article on "Up to eleven").
#
# NOTE: the image of a black cat in a coal mine obviously requires this
# limit, but some more valid images can get very close; well over 8MByte.
#
# COMPRESSION_BUFFER_LIMIT
# This is the (overrideable) default for the amount of memory libpng will
# buffer before selecting a filter for a row. It is limited itself to
# COMPRESSION_BUFFER_MAX as values above that level make no change (see the
# previous paragraph.)
#
# See png.h for more description of these options.
option WRITE_FILTER requires WRITE
option SELECT_FILTER requires WRITE_FILTER disabled
setting COMPRESSION_BUFFER_MAX default 8453377
setting COMPRESSION_BUFFER_LIMIT default 8453377
option SELECT_FILTER requires WRITE_FILTER
# added at libpng-1.5.4

4
scripts/pnglibconf.h.prebuilt
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@@ -100,7 +100,7 @@
#define PNG_READ_tRNS_SUPPORTED
#define PNG_READ_zTXt_SUPPORTED
#define PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
/*#undef PNG_SELECT_FILTER_SUPPORTED*/
#define PNG_SELECT_FILTER_SUPPORTED
#define PNG_SEQUENTIAL_READ_SUPPORTED
#define PNG_SETJMP_SUPPORTED
#define PNG_SETTING_SUPPORTED
@@ -192,8 +192,6 @@
/* settings */
#define PNG_ABORT { (abort()); }
#define PNG_API_RULE 0
#define PNG_COMPRESSION_BUFFER_LIMIT 8453377
#define PNG_COMPRESSION_BUFFER_MAX 8453377
#define PNG_DEFAULT_GAMMA_ACCURACY 665
#define PNG_DEFAULT_READ_MACROS 1
#define PNG_GAMMA_THRESHOLD_FIXED 153