/* pngrutil.c - utilities to read a PNG file * * Copyright (c) 2018-2024 Cosmin Truta * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson * Copyright (c) 1996-1997 Andreas Dilger * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc. * * This code is released under the libpng license. * For conditions of distribution and use, see the disclaimer * and license in png.h * * This file contains routines that are only called from within * libpng itself during the course of reading an image. */ #include "pngpriv.h" #ifdef PNG_READ_SUPPORTED png_uint_32 PNGAPI png_get_uint_31(png_const_structrp png_ptr, png_const_bytep buf) { … } #if defined(PNG_READ_gAMA_SUPPORTED) || defined(PNG_READ_cHRM_SUPPORTED) /* The following is a variation on the above for use with the fixed * point values used for gAMA and cHRM. Instead of png_error it * issues a warning and returns (-1) - an invalid value because both * gAMA and cHRM use *unsigned* integers for fixed point values. */ #define PNG_FIXED_ERROR … static png_fixed_point /* PRIVATE */ png_get_fixed_point(png_structrp png_ptr, png_const_bytep buf) { … } #endif #ifdef PNG_READ_INT_FUNCTIONS_SUPPORTED /* NOTE: the read macros will obscure these definitions, so that if * PNG_USE_READ_MACROS is set the library will not use them internally, * but the APIs will still be available externally. * * The parentheses around "PNGAPI function_name" in the following three * functions are necessary because they allow the macros to co-exist with * these (unused but exported) functions. */ /* Grab an unsigned 32-bit integer from a buffer in big-endian format. */ png_uint_32 (PNGAPI png_get_uint_32)(png_const_bytep buf) { … } /* Grab a signed 32-bit integer from a buffer in big-endian format. The * data is stored in the PNG file in two's complement format and there * is no guarantee that a 'png_int_32' is exactly 32 bits, therefore * the following code does a two's complement to native conversion. */ png_int_32 (PNGAPI png_get_int_32)(png_const_bytep buf) { … } /* Grab an unsigned 16-bit integer from a buffer in big-endian format. */ png_uint_16 (PNGAPI png_get_uint_16)(png_const_bytep buf) { … } #endif /* READ_INT_FUNCTIONS */ /* Read and check the PNG file signature */ void /* PRIVATE */ png_read_sig(png_structrp png_ptr, png_inforp info_ptr) { … } /* Read the chunk header (length + type name). * Put the type name into png_ptr->chunk_name, and return the length. */ png_uint_32 /* PRIVATE */ png_read_chunk_header(png_structrp png_ptr) { … } /* Read data, and (optionally) run it through the CRC. */ void /* PRIVATE */ png_crc_read(png_structrp png_ptr, png_bytep buf, png_uint_32 length) { … } /* Optionally skip data and then check the CRC. Depending on whether we * are reading an ancillary or critical chunk, and how the program has set * things up, we may calculate the CRC on the data and print a message. * Returns '1' if there was a CRC error, '0' otherwise. */ int /* PRIVATE */ png_crc_finish(png_structrp png_ptr, png_uint_32 skip) { … } /* Compare the CRC stored in the PNG file with that calculated by libpng from * the data it has read thus far. */ int /* PRIVATE */ png_crc_error(png_structrp png_ptr) { … } #if defined(PNG_READ_iCCP_SUPPORTED) || defined(PNG_READ_iTXt_SUPPORTED) ||\ defined(PNG_READ_pCAL_SUPPORTED) || defined(PNG_READ_sCAL_SUPPORTED) ||\ defined(PNG_READ_sPLT_SUPPORTED) || defined(PNG_READ_tEXt_SUPPORTED) ||\ defined(PNG_READ_zTXt_SUPPORTED) || defined(PNG_SEQUENTIAL_READ_SUPPORTED) /* Manage the read buffer; this simply reallocates the buffer if it is not small * enough (or if it is not allocated). The routine returns a pointer to the * buffer; if an error occurs and 'warn' is set the routine returns NULL, else * it will call png_error (via png_malloc) on failure. (warn == 2 means * 'silent'). */ static png_bytep png_read_buffer(png_structrp png_ptr, png_alloc_size_t new_size, int warn) { … } #endif /* READ_iCCP|iTXt|pCAL|sCAL|sPLT|tEXt|zTXt|SEQUENTIAL_READ */ /* png_inflate_claim: claim the zstream for some nefarious purpose that involves * decompression. Returns Z_OK on success, else a zlib error code. It checks * the owner but, in final release builds, just issues a warning if some other * chunk apparently owns the stream. Prior to release it does a png_error. */ static int png_inflate_claim(png_structrp png_ptr, png_uint_32 owner) { … } #if ZLIB_VERNUM >= 0x1240 /* Handle the start of the inflate stream if we called inflateInit2(strm,0); * in this case some zlib versions skip validation of the CINFO field and, in * certain circumstances, libpng may end up displaying an invalid image, in * contrast to implementations that call zlib in the normal way (e.g. libpng * 1.5). */ int /* PRIVATE */ png_zlib_inflate(png_structrp png_ptr, int flush) { … } #endif /* Zlib >= 1.2.4 */ #ifdef PNG_READ_COMPRESSED_TEXT_SUPPORTED #if defined(PNG_READ_zTXt_SUPPORTED) || defined (PNG_READ_iTXt_SUPPORTED) /* png_inflate now returns zlib error codes including Z_OK and Z_STREAM_END to * allow the caller to do multiple calls if required. If the 'finish' flag is * set Z_FINISH will be passed to the final inflate() call and Z_STREAM_END must * be returned or there has been a problem, otherwise Z_SYNC_FLUSH is used and * Z_OK or Z_STREAM_END will be returned on success. * * The input and output sizes are updated to the actual amounts of data consumed * or written, not the amount available (as in a z_stream). The data pointers * are not changed, so the next input is (data+input_size) and the next * available output is (output+output_size). */ static int png_inflate(png_structrp png_ptr, png_uint_32 owner, int finish, /* INPUT: */ png_const_bytep input, png_uint_32p input_size_ptr, /* OUTPUT: */ png_bytep output, png_alloc_size_t *output_size_ptr) { … } /* * Decompress trailing data in a chunk. The assumption is that read_buffer * points at an allocated area holding the contents of a chunk with a * trailing compressed part. What we get back is an allocated area * holding the original prefix part and an uncompressed version of the * trailing part (the malloc area passed in is freed). */ static int png_decompress_chunk(png_structrp png_ptr, png_uint_32 chunklength, png_uint_32 prefix_size, png_alloc_size_t *newlength /* must be initialized to the maximum! */, int terminate /*add a '\0' to the end of the uncompressed data*/) { … } #endif /* READ_zTXt || READ_iTXt */ #endif /* READ_COMPRESSED_TEXT */ #ifdef PNG_READ_iCCP_SUPPORTED /* Perform a partial read and decompress, producing 'avail_out' bytes and * reading from the current chunk as required. */ static int png_inflate_read(png_structrp png_ptr, png_bytep read_buffer, uInt read_size, png_uint_32p chunk_bytes, png_bytep next_out, png_alloc_size_t *out_size, int finish) { … } #endif /* READ_iCCP */ /* Read and check the IDHR chunk */ void /* PRIVATE */ png_handle_IHDR(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } /* Read and check the palette */ void /* PRIVATE */ png_handle_PLTE(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } void /* PRIVATE */ png_handle_IEND(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #ifdef PNG_READ_gAMA_SUPPORTED void /* PRIVATE */ png_handle_gAMA(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_sBIT_SUPPORTED void /* PRIVATE */ png_handle_sBIT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_cHRM_SUPPORTED void /* PRIVATE */ png_handle_cHRM(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_sRGB_SUPPORTED void /* PRIVATE */ png_handle_sRGB(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif /* READ_sRGB */ #ifdef PNG_READ_iCCP_SUPPORTED void /* PRIVATE */ png_handle_iCCP(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) /* Note: this does not properly handle profiles that are > 64K under DOS */ { … } #endif /* READ_iCCP */ #ifdef PNG_READ_sPLT_SUPPORTED void /* PRIVATE */ png_handle_sPLT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) /* Note: this does not properly handle chunks that are > 64K under DOS */ { … } #endif /* READ_sPLT */ #ifdef PNG_READ_tRNS_SUPPORTED void /* PRIVATE */ png_handle_tRNS(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_bKGD_SUPPORTED void /* PRIVATE */ png_handle_bKGD(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_eXIf_SUPPORTED void /* PRIVATE */ png_handle_eXIf(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_hIST_SUPPORTED void /* PRIVATE */ png_handle_hIST(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_pHYs_SUPPORTED void /* PRIVATE */ png_handle_pHYs(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_oFFs_SUPPORTED void /* PRIVATE */ png_handle_oFFs(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_pCAL_SUPPORTED /* Read the pCAL chunk (described in the PNG Extensions document) */ void /* PRIVATE */ png_handle_pCAL(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_sCAL_SUPPORTED /* Read the sCAL chunk */ void /* PRIVATE */ png_handle_sCAL(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_tIME_SUPPORTED void /* PRIVATE */ png_handle_tIME(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_tEXt_SUPPORTED /* Note: this does not properly handle chunks that are > 64K under DOS */ void /* PRIVATE */ png_handle_tEXt(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_zTXt_SUPPORTED /* Note: this does not correctly handle chunks that are > 64K under DOS */ void /* PRIVATE */ png_handle_zTXt(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_iTXt_SUPPORTED /* Note: this does not correctly handle chunks that are > 64K under DOS */ void /* PRIVATE */ png_handle_iTXt(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length) { … } #endif #ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED /* Utility function for png_handle_unknown; set up png_ptr::unknown_chunk */ static int png_cache_unknown_chunk(png_structrp png_ptr, png_uint_32 length) { … } #endif /* READ_UNKNOWN_CHUNKS */ /* Handle an unknown, or known but disabled, chunk */ void /* PRIVATE */ png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length, int keep) { … } /* This function is called to verify that a chunk name is valid. * This function can't have the "critical chunk check" incorporated * into it, since in the future we will need to be able to call user * functions to handle unknown critical chunks after we check that * the chunk name itself is valid. */ /* Bit hacking: the test for an invalid byte in the 4 byte chunk name is: * * ((c) < 65 || (c) > 122 || ((c) > 90 && (c) < 97)) */ void /* PRIVATE */ png_check_chunk_name(png_const_structrp png_ptr, png_uint_32 chunk_name) { … } void /* PRIVATE */ png_check_chunk_length(png_const_structrp png_ptr, png_uint_32 length) { … } /* Combines the row recently read in with the existing pixels in the row. This * routine takes care of alpha and transparency if requested. This routine also * handles the two methods of progressive display of interlaced images, * depending on the 'display' value; if 'display' is true then the whole row * (dp) is filled from the start by replicating the available pixels. If * 'display' is false only those pixels present in the pass are filled in. */ void /* PRIVATE */ png_combine_row(png_const_structrp png_ptr, png_bytep dp, int display) { … } #ifdef PNG_READ_INTERLACING_SUPPORTED void /* PRIVATE */ png_do_read_interlace(png_row_infop row_info, png_bytep row, int pass, png_uint_32 transformations /* Because these may affect the byte layout */) { … } #endif /* READ_INTERLACING */ static void png_read_filter_row_sub(png_row_infop row_info, png_bytep row, png_const_bytep prev_row) { … } static void png_read_filter_row_up(png_row_infop row_info, png_bytep row, png_const_bytep prev_row) { … } static void png_read_filter_row_avg(png_row_infop row_info, png_bytep row, png_const_bytep prev_row) { … } static void png_read_filter_row_paeth_1byte_pixel(png_row_infop row_info, png_bytep row, png_const_bytep prev_row) { … } static void png_read_filter_row_paeth_multibyte_pixel(png_row_infop row_info, png_bytep row, png_const_bytep prev_row) { … } static void png_init_filter_functions(png_structrp pp) /* This function is called once for every PNG image (except for PNG images * that only use PNG_FILTER_VALUE_NONE for all rows) to set the * implementations required to reverse the filtering of PNG rows. Reversing * the filter is the first transformation performed on the row data. It is * performed in place, therefore an implementation can be selected based on * the image pixel format. If the implementation depends on image width then * take care to ensure that it works correctly if the image is interlaced - * interlacing causes the actual row width to vary. */ { … } void /* PRIVATE */ png_read_filter_row(png_structrp pp, png_row_infop row_info, png_bytep row, png_const_bytep prev_row, int filter) { … } #ifdef PNG_SEQUENTIAL_READ_SUPPORTED void /* PRIVATE */ png_read_IDAT_data(png_structrp png_ptr, png_bytep output, png_alloc_size_t avail_out) { … } void /* PRIVATE */ png_read_finish_IDAT(png_structrp png_ptr) { … } void /* PRIVATE */ png_read_finish_row(png_structrp png_ptr) { … } #endif /* SEQUENTIAL_READ */ void /* PRIVATE */ png_read_start_row(png_structrp png_ptr) { … } #endif /* READ */
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