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5652acdd48
Palette index checking: checking on read was erroneously skipped. pngcp can now turn off the palette index checking or fix the errors (mainly to allow comparison with libpng 1.6, which defaulted to ignoring it). The API now documents how the 'enabled' parameter works. On read the check is on by default (it was apparently off in libpng 1.6) however now if explicitly turned on the warning message is stopped, this provides better interaction with get_palette_max at the cost of a small API change (may need to be reviewed.) Palette size errors: invalid entries in the palette are now set to #beaded to make the errors more obvious and allow easy detection in memory. Read transform pipeline caching: changes to fix the palette index check (which are erroneously cached), the pipeline can now contain multiple caches. E.g. caching of packing of palette indices can be combined with caching of palette RGB transforms. Read code now checks for callbacks to read 0 data (and faults them). Fixed the reading of PNGs with multiple 0 length IDATs that failed as a result plus the handling of zero length unknown. (Which occurs, validly; the spurious warning has been removed). filter selection: the 1.6 and earlier sum of absolute differences algorithm has been reintroduced with an option to disfavor some filters over others where the sums are close (not yet exposed). The selection code also logs the last known occurence of each possible byte code across multiple lines. This allows detection of PNG images with lower bit depth than the format implies and, therefore, allows the filtering to be turned off in those cases as well. The default write zlib settings are still lower than libpng16. The selection algorithm is being refined (the overall results are worse than not doing any filtering). Signed-off-by: John Bowler <jbowler@acm.org>
115 lines
3.8 KiB
C
115 lines
3.8 KiB
C
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/* pngrio.c - functions for data input
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*
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* Last changed in libpng 1.7.0 [(PENDING RELEASE)]
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* Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
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* (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
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* (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
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*
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* This code is released under the libpng license.
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* For conditions of distribution and use, see the disclaimer
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* and license in png.h
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*
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* This file provides a location for all input. Users who need
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* special handling are expected to write a function that has the same
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* arguments as this and performs a similar function, but that possibly
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* has a different input method. Note that you shouldn't change this
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* function, but rather write a replacement function and then make
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* libpng use it at run time with png_set_read_fn(...).
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*/
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#include "pngpriv.h"
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#define PNG_SRC_FILE PNG_SRC_FILE_pngrio
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#ifdef PNG_READ_SUPPORTED
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/* Read the data from whatever input you are using. The default routine
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* reads from a file pointer. Note that this routine sometimes gets called
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* with very small lengths, so you should implement some kind of simple
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* buffering if you are using unbuffered reads. This should never be asked
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* to read more than 64K on a 16 bit machine.
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*/
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void /* PRIVATE */
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png_read_data(png_structrp png_ptr, png_voidp data, png_size_t length)
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{
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png_debug1(4, "reading %d bytes", (int)length);
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/* This was guaranteed by prior versions of libpng, so app callbacks may
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* assume it even though it isn't documented to be the case.
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*/
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debug(length > 0U);
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if (png_ptr->rw_data_fn != NULL)
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png_ptr->rw_data_fn(png_ptr, png_voidcast(png_bytep,data), length);
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else
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png_app_error(png_ptr, "No read function");
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}
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#ifdef PNG_STDIO_SUPPORTED
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/* This is the function that does the actual reading of data. If you are
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* not reading from a standard C stream, you should create a replacement
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* read_data function and use it at run time with png_set_read_fn(), rather
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* than changing the library.
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*/
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void PNGCBAPI
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png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
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{
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png_size_t check;
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if (png_ptr == NULL)
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return;
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/* fread() returns 0 on error, so it is OK to store this in a png_size_t
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* instead of an int, which is what fread() actually returns.
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*/
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check = fread(data, 1, length, png_voidcast(png_FILE_p, png_ptr->io_ptr));
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if (check != length)
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png_error(png_ptr, "Read Error");
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}
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#endif /* STDIO */
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/* This function allows the application to supply a new input function
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* for libpng if standard C streams aren't being used.
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*
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* This function takes as its arguments:
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*
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* png_ptr - pointer to a png input data structure
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*
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* io_ptr - pointer to user supplied structure containing info about
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* the input functions. May be NULL.
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*
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* read_data_fn - pointer to a new input function that takes as its
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* arguments a pointer to a png_struct, a pointer to
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* a location where input data can be stored, and a 32-bit
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* unsigned int that is the number of bytes to be read.
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* To exit and output any fatal error messages the new write
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* function should call png_error(png_ptr, "Error msg").
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* May be NULL, in which case libpng's default function will
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* be used.
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*/
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void PNGAPI
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png_set_read_fn(png_structrp png_ptr, png_voidp io_ptr,
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png_rw_ptr read_data_fn)
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{
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if (png_ptr == NULL)
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return;
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if (!png_ptr->read_struct)
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{
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png_app_error(png_ptr, "cannot set a read function on a write struct");
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return;
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}
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if (read_data_fn == NULL)
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{
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png_app_error(png_ptr, "API change: png_set_read_fn requires a function");
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return;
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}
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png_ptr->io_ptr = io_ptr;
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png_ptr->rw_data_fn = read_data_fn;
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}
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#endif /* READ */
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