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Write code update

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Implemented better defaulting of zlib settings based on image properties.
Implemented pass-through of png_write_rows when the rows can be used directly (a
common case) optimizing the handling of previous-row buffering.

Removed the METHODICAL filter selection method and disabled the HEURISTIC one;
the first was ridiculously slow (though useful for experiments) the second
doesn't work.  Filter selection is temporarily disabled (it defaults to the
lowest numbered filter in the list; typically 'none').

New handling of compression settings (incomplete), new PNG compression level
(not yet visible in an API).

Back ported 'PNG_FAST_FILTERS' from 1.6 (in png.h).

There are minimal API changes beyond removal of the selection options.  Work is
still to be done to investigate a filter selection mechanism that is at least as
good as the previous one.

Signed-off-by: John Bowler <jbowler@acm.org>
This commit is contained in:
John Bowler
2016-05-04 17:02:20 -07:00
parent 1fd42d849d
commit cde9b583a8
10 changed files with 1834 additions and 1330 deletions
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22
pngpriv.h
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@@ -1080,10 +1080,6 @@ PNG_INTERNAL_FUNCTION(int,png_crc_finish,(png_structrp png_ptr,
PNG_INTERNAL_FUNCTION(void,png_calculate_crc,(png_structrp png_ptr,
png_const_voidp ptr, png_size_t length),PNG_EMPTY);
#ifdef PNG_WRITE_FLUSH_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_flush,(png_structrp png_ptr),PNG_EMPTY);
#endif
/* Write various chunks */
/* Write the IHDR chunk, and update the png_struct with the necessary
@@ -1199,9 +1195,9 @@ PNG_INTERNAL_FUNCTION(void,png_write_sCAL_s,(png_structrp png_ptr,
#endif
#ifdef PNG_WRITE_SUPPORTED
/* Initialize the row compression mechanism. */
PNG_INTERNAL_FUNCTION(void, png_write_start_IDAT, (png_structp png_ptr),
PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_write_start_IDAT,(png_structrp png_ptr),
PNG_EMPTY);
/* Do any required initialization before IDAT or row processing starts. */
/* Choose the best filter to use and filter the row data then write it out. If
* WRITE_FILTERING is not supported this just writes the data out with a zero
@@ -1226,11 +1222,21 @@ enum
# define PNG_IDAT_END(f) (((f) & ~png_pass_first_row) == \
(png_row_end+png_pass_last_row+png_pass_last))
};
PNG_INTERNAL_FUNCTION(void, png_write_filter_row, (png_structrp png_ptr,
PNG_INTERNAL_FUNCTION(void,png_write_png_data,(png_structrp png_ptr,
png_bytep prev_pixels, png_const_bytep unfiltered_row, png_uint_32 x,
unsigned int width/*pixels*/, unsigned int row_info_flags),
PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_write_png_rows,(png_structrp png_ptr,
png_const_bytep *rows, png_uint_32 num_rows), PNG_EMPTY);
/* As above but rows[num_rows] of correctly (PNG) formated but unfiltered
* data are passed in. For an interlaced image the rows will be interlaced
* rows and therefore may be narrower than the image width.
*
* This function advances png_structp::pass and png_structp::row_number as
* required.
*/
/* Release memory used by the deflate mechanism */
PNG_INTERNAL_FUNCTION(void, png_deflate_destroy, (png_structp png_ptr),
PNG_EMPTY);