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Imported from libpng-1.0.7beta12.tar

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Glenn Randers-Pehrson
2000-05-12 06:19:53 -05:00
parent 752945701e
commit 1ef65b6742
41 changed files with 390 additions and 272 deletions
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112
libpng.txt
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@@ -1,6 +1,6 @@
libpng.txt - A description on how to use and modify libpng
libpng version 1.0.7beta11 - May 6, 2000
libpng version 1.0.7beta12 - May 12, 2000
Updated and distributed by Glenn Randers-Pehrson
<randeg@alum.rpi.edu>
Copyright (c) 1998, 1999, 2000 Glenn Randers-Pehrson
@@ -552,7 +552,7 @@ into the info_ptr is returned for any complex types.
text_ptr[i].key - keyword for comment. Must contain
1-79 characters.
text_ptr[i].text - text comments for current
keyword. Can empty.
keyword. Can be empty.
text_ptr[i].text_length - length of text string,
after decompression, 0 for iTXt
text_ptr[i].itxt_length - length of itxt string,
@@ -1182,15 +1182,17 @@ It is also possible to individually free the info_ptr members that
point to libpng-allocated storage with the following functions:
png_free_data(png_ptr, info_ptr, mask, n)
mask - identifies data to be freed, a mask
containing the logical OR of one or more of
PNG_FREE_PLTE, PNG_FREE_TRNS,
PNG_FREE_HIST, PNG_FREE_ICCP,
PNG_FREE_SPLT, PNG_FREE_ROWS,
PNG_FREE_TEXT, PNG_FREE_UNKN,
or simply PNG_FREE_ALL
n - sequence number of item to be freed
(-1 for all items)
mask - identifies data to be freed, a mask
containing the logical OR of one or
more of
PNG_FREE_PLTE, PNG_FREE_TRNS,
PNG_FREE_HIST, PNG_FREE_ICCP,
PNG_FREE_PCAL, PNG_FREE_ROWS,
PNG_FREE_SCAL, PNG_FREE_SPLT,
PNG_FREE_TEXT, PNG_FREE_UNKN,
or simply PNG_FREE_ALL
n - sequence number of item to be freed
(-1 for all items)
These functions may be safely called when the relevant storage has
already been freed, or has not yet been allocated, or was allocated
@@ -1206,12 +1208,12 @@ or so that it will free data that was allocated by the user with png_malloc()
or png_zalloc() and passed in via a png_set_*() function, with
png_data_freer(png_ptr, info_ptr, freer, mask)
mask - which data elements are affected
same choices as in png_free_data()
freer - one of
PNG_DESTROY_WILL_FREE_DATA
PNG_SET_WILL_FREE_DATA
PNG_USER_WILL_FREE_DATA
mask - which data elements are affected
same choices as in png_free_data()
freer - one of
PNG_DESTROY_WILL_FREE_DATA
PNG_SET_WILL_FREE_DATA
PNG_USER_WILL_FREE_DATA
This function only affects data that has already been allocated.
You can call this function after reading the PNG data but before calling
@@ -1220,13 +1222,23 @@ function is responsible for freeing any existing data that might be present,
and again after the png_set_*() functions to control whether the user
or png_destroy_*() is supposed to free the data. When the user assumes
responsibility for libpng-allocated data, the application must use
png_free() to free it.
png_free() to free it, and when the user transfers responsibility to libpng
for data that the user has allocated, the user must have used png_malloc()
or png_zalloc() to allocate it (the png_zalloc() function is the same
as png_malloc() except that it also zeroes the newly-allocated memory).
If you allocated your row_pointers in a single block, as suggested above in
the description of the high level read interface, you must not transfer
responsibility for freeing it to the png_set_rows or png_read_destroy function,
because they would also try to free the individual row_pointers[i].
If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
separately, do not transfer responsibility for freeing text_ptr to libpng,
because when libpng fills a png_text structure it combines these members with
the key member, and png_free_data() will free only text_ptr.key. Similarly,
if you transfer responsibility for free'ing text_ptr from libpng to your
application, your application must not separately free those members.
For a more compact example of reading a PNG image, see the file example.c.
Reading PNG files progressively
@@ -1867,7 +1879,8 @@ transformations are permitted, enabled by the following masks.
PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
PNG_TRANSFORM_STRIP_FILLER Strip out filler bytes.
If you have valid image data in the info structure, simply do this:
If you have valid image data in the info structure (you can use
png_set_rows() to put image data in the info structure), simply do this:
png_write_png(png_ptr, info_ptr, png_transforms, NULL)
@@ -2127,15 +2140,17 @@ It is also possible to individually free the info_ptr members that
point to libpng-allocated storage with the following functions:
png_free_data(png_ptr, info_ptr, mask, n)
mask - identifies data to be freed, a mask
containing the logical OR of one or more of
PNG_FREE_PLTE, PNG_FREE_TRNS,
PNG_FREE_HIST, PNG_FREE_ICCP,
PNG_FREE_SPLT, PNG_FREE_ROWS,
PNG_FREE_TEXT, PNG_FREE_UNKN,
or simply PNG_FREE_ALL
n - sequence number of item to be freed
(-1 for all items)
mask - identifies data to be freed, a mask
containing the logical OR of one or
more of
PNG_FREE_PLTE, PNG_FREE_TRNS,
PNG_FREE_HIST, PNG_FREE_ICCP,
PNG_FREE_PCAL, PNG_FREE_ROWS,
PNG_FREE_SCAL, PNG_FREE_SPLT,
PNG_FREE_TEXT, PNG_FREE_UNKN,
or simply PNG_FREE_ALL
n - sequence number of item to be freed
(-1 for all items)
These functions may be safely called when the relevant storage has
already been freed, or has not yet been allocated, or was allocated
@@ -2155,12 +2170,12 @@ or so that it will free data that was allocated by the user with png_malloc()
or png_zalloc() and passed in via a png_set_*() function, with
png_data_freer(png_ptr, info_ptr, freer, mask)
mask - which data elements are affected
same choices as in png_free_data()
freer - one of
PNG_DESTROY_WILL_FREE_DATA
PNG_SET_WILL_FREE_DATA
PNG_USER_WILL_FREE_DATA
mask - which data elements are affected
same choices as in png_free_data()
freer - one of
PNG_DESTROY_WILL_FREE_DATA
PNG_SET_WILL_FREE_DATA
PNG_USER_WILL_FREE_DATA
For example, to transfer responsibility for some data from a read structure
to a write structure, you could use
@@ -2182,8 +2197,17 @@ This function only affects data that has already been allocated.
You can call this function before calling after the png_set_*() functions
to control whether the user or png_destroy_*() is supposed to free the data.
When the user assumes responsibility for libpng-allocated data, the
application must use png_free() to free it.
application must use
png_free() to free it, and when the user transfers responsibility to libpng
for data that the user has allocated, the user must have used png_malloc()
or png_zalloc() to allocate it.
If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
separately, do not transfer responsibility for freeing text_ptr to libpng,
because when libpng fills a png_text structure it combines these members with
the key member, and png_free_data() will free only text_ptr.key. Similarly,
if you transfer responsibility for free'ing text_ptr from libpng to your
application, your application must not separately free those members.
For a more compact example of writing a PNG image, see the file example.c.
V. Modifying/Customizing libpng:
@@ -2573,15 +2597,29 @@ png_set_error_fn(), which is essentially the same function, but with a new
name to force compilation errors with applications that try to use the old
method.
Starting with version 1.0.7, you can find out which version of the library
you are using at run-time:
png_uint_32 libpng_vn = png_access_version_number();
The number libpng_vn is constructed from the major version, minor
version with leading zero, and release number with leading zero,
(e.g., libpng_vn for version 1.0.7 is 10007).
You can also check which version of png.h you used when compiling your
application:
png_uint_32 application_vn = PNG_LIBPNG_VER;
VII. Y2K Compliance in libpng
May 6, 2000
May 12, 2000
Since the PNG Development group is an ad-hoc body, we can't make
an official declaration.
This is your unofficial assurance that libpng from version 0.71 and
upward through 1.0.7beta11 are Y2K compliant. It is my belief that earlier
upward through 1.0.7beta12 are Y2K compliant. It is my belief that earlier
versions were also Y2K compliant.
Libpng only has three year fields. One is a 2-byte unsigned integer that