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[devel] Fix the read/write row callback documentation.

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John Bowler 2011-02-16 06:16:31 -06:00 committed by Glenn Randers-Pehrson
parent cd11345693
commit 59010e53f4
2 changed files with 54 additions and 0 deletions
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27
libpng-manual.txt
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@ -513,6 +513,19 @@ To inform libpng about your function, use
png_set_read_status_fn(png_ptr, read_row_callback);
When this function is called the row has already been completely processed and
the 'row' and 'pass' refer to the next row to be handled. For the
non-interlaced case the row that was just handled is simply one less than the
passed in row number, and pass will always be 0. For the interlaced case the
same applies unless the row value is 0, in which case the row just handled was
the last one from one of the preceding passes. Because interlacing may skip a
pass you cannot be sure that the preceding pass is just 'pass-1', if you really
need to know what the last pass is record (row,pass) from the callback and use
the last recorded value each time.
As with the user transform you can find the output row using the
PNG_ROW_FROM_PASS_ROW macro.
Unknown-chunk handling
Now you get to set the way the library processes unknown chunks in the
@ -2224,6 +2237,20 @@ To inform libpng about your function, use
png_set_write_status_fn(png_ptr, write_row_callback);
When this function is called the row has already been completely processed and
it has also been written out. The 'row' and 'pass' refer to the next row to be
handled. For the
non-interlaced case the row that was just handled is simply one less than the
passed in row number, and pass will always be 0. For the interlaced case the
same applies unless the row value is 0, in which case the row just handled was
the last one from one of the preceding passes. Because interlacing may skip a
pass you cannot be sure that the preceding pass is just 'pass-1', if you really
need to know what the last pass is record (row,pass) from the callback and use
the last recorded value each time.
As with the user transform you can find the output row using the
PNG_ROW_FROM_PASS_ROW macro.
You now have the option of modifying how the compression library will
run. The following functions are mainly for testing, but may be useful
in some cases, like if you need to write PNG files extremely fast and

27
libpng.3
View File

@ -1440,6 +1440,19 @@ To inform libpng about your function, use
png_set_read_status_fn(png_ptr, read_row_callback);
When this function is called the row has already been completely processed and
the 'row' and 'pass' refer to the next row to be handled. For the
non-interlaced case the row that was just handled is simply one less than the
passed in row number, and pass will always be 0. For the interlaced case the
same applies unless the row value is 0, in which case the row just handled was
the last one from one of the preceding passes. Because interlacing may skip a
pass you cannot be sure that the preceding pass is just 'pass-1', if you really
need to know what the last pass is record (row,pass) from the callback and use
the last recorded value each time.
As with the user transform you can find the output row using the
PNG_ROW_FROM_PASS_ROW macro.
.SS Unknown-chunk handling
Now you get to set the way the library processes unknown chunks in the
@ -3151,6 +3164,20 @@ To inform libpng about your function, use
png_set_write_status_fn(png_ptr, write_row_callback);
When this function is called the row has already been completely processed and
it has also been written out. The 'row' and 'pass' refer to the next row to be
handled. For the
non-interlaced case the row that was just handled is simply one less than the
passed in row number, and pass will always be 0. For the interlaced case the
same applies unless the row value is 0, in which case the row just handled was
the last one from one of the preceding passes. Because interlacing may skip a
pass you cannot be sure that the preceding pass is just 'pass-1', if you really
need to know what the last pass is record (row,pass) from the callback and use
the last recorded value each time.
As with the user transform you can find the output row using the
PNG_ROW_FROM_PASS_ROW macro.
You now have the option of modifying how the compression library will
run. The following functions are mainly for testing, but may be useful
in some cases, like if you need to write PNG files extremely fast and