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pnginfo.h
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pnginfo.h
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/* pnginfo.h - header file for PNG reference library
*
* Copyright (c) 2018 Cosmin Truta
* Copyright (c) 1998-2002,2004,2006-2013,2018 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
*/
/* png_info is a structure that holds the information in a PNG file so
* that the application can find out the characteristics of the image.
* If you are reading the file, this structure will tell you what is
* in the PNG file. If you are writing the file, fill in the information
* you want to put into the PNG file, using png_set_*() functions, then
* call png_write_info().
*
* The names chosen should be very close to the PNG specification, so
* consult that document for information about the meaning of each field.
*
* With libpng < 0.95, it was only possible to directly set and read the
* the values in the png_info_struct, which meant that the contents and
* order of the values had to remain fixed. With libpng 0.95 and later,
* however, there are now functions that abstract the contents of
* png_info_struct from the application, so this makes it easier to use
* libpng with dynamic libraries, and even makes it possible to use
* libraries that don't have all of the libpng ancillary chunk-handing
* functionality. In libpng-1.5.0 this was moved into a separate private
* file that is not visible to applications.
*
* The following members may have allocated storage attached that should be
* cleaned up before the structure is discarded: palette, trans, text,
* pcal_purpose, pcal_units, pcal_params, hist, iccp_name, iccp_profile,
* splt_palettes, scal_unit, row_pointers, and unknowns. By default, these
* are automatically freed when the info structure is deallocated, if they were
* allocated internally by libpng. This behavior can be changed by means
* of the png_data_freer() function.
*
* More allocation details: all the chunk-reading functions that
* change these members go through the corresponding png_set_*
* functions. A function to clear these members is available: see
* png_free_data(). The png_set_* functions do not depend on being
* able to point info structure members to any of the storage they are
* passed (they make their own copies), EXCEPT that the png_set_text
* functions use the same storage passed to them in the text_ptr or
* itxt_ptr structure argument, and the png_set_rows and png_set_unknowns
* functions do not make their own copies.
*/
#ifndef PNGINFO_H
#define PNGINFO_H
struct png_info_def
{
/* The following are necessary for every PNG file */
png_uint_32 width; /* width of image in pixels (from IHDR) */
png_uint_32 height; /* height of image in pixels (from IHDR) */
png_uint_32 valid; /* valid chunk data (see PNG_INFO_ below) */
size_t rowbytes; /* bytes needed to hold an untransformed row */
png_colorp palette; /* array of color values (valid & PNG_INFO_PLTE) */
png_uint_16 num_palette; /* number of color entries in "palette" (PLTE) */
png_uint_16 num_trans; /* number of transparent palette color (tRNS) */
png_byte bit_depth; /* 1, 2, 4, 8, or 16 bits/channel (from IHDR) */
png_byte color_type; /* see PNG_COLOR_TYPE_ below (from IHDR) */
/* The following three should have been named *_method not *_type */
png_byte compression_type; /* must be PNG_COMPRESSION_TYPE_BASE (IHDR) */
png_byte filter_type; /* must be PNG_FILTER_TYPE_BASE (from IHDR) */
png_byte interlace_type; /* One of PNG_INTERLACE_NONE, PNG_INTERLACE_ADAM7 */
/* The following are set by png_set_IHDR, called from the application on
* write, but the are never actually used by the write code.
*/
png_byte channels; /* number of data channels per pixel (1, 2, 3, 4) */
png_byte pixel_depth; /* number of bits per pixel */
png_byte spare_byte; /* to align the data, and for future use */
#ifdef PNG_READ_SUPPORTED
/* This is never set during write */
png_byte signature[8]; /* magic bytes read by libpng from start of file */
#endif
/* The rest of the data is optional. If you are reading, check the
* valid field to see if the information in these are valid. If you
* are writing, set the valid field to those chunks you want written,
* and initialize the appropriate fields below.
*/
#if defined(PNG_COLORSPACE_SUPPORTED) || defined(PNG_GAMMA_SUPPORTED)
/* png_colorspace only contains 'flags' if neither GAMMA or COLORSPACE are
* defined. When COLORSPACE is switched on all the colorspace-defining
* chunks should be enabled, when GAMMA is switched on all the gamma-defining
* chunks should be enabled. If this is not done it becomes possible to read
* inconsistent PNG files and assign a probably incorrect interpretation to
* the information. (In other words, by carefully choosing which chunks to
* recognize the system configuration can select an interpretation for PNG
* files containing ambiguous data and this will result in inconsistent
* behavior between different libpng builds!)
*/
png_colorspace colorspace;
#endif
#ifdef PNG_iCCP_SUPPORTED
/* iCCP chunk data. */
png_charp iccp_name; /* profile name */
png_bytep iccp_profile; /* International Color Consortium profile data */
png_uint_32 iccp_proflen; /* ICC profile data length */
#endif
#ifdef PNG_TEXT_SUPPORTED
/* The tEXt, and zTXt chunks contain human-readable textual data in
* uncompressed, compressed, and optionally compressed forms, respectively.
* The data in "text" is an array of pointers to uncompressed,
* null-terminated C strings. Each chunk has a keyword that describes the
* textual data contained in that chunk. Keywords are not required to be
* unique, and the text string may be empty. Any number of text chunks may
* be in an image.
*/
int num_text; /* number of comments read or comments to write */
int max_text; /* current size of text array */
png_textp text; /* array of comments read or comments to write */
#endif /* TEXT */
#ifdef PNG_tIME_SUPPORTED
/* The tIME chunk holds the last time the displayed image data was
* modified. See the png_time struct for the contents of this struct.
*/
png_time mod_time;
#endif
#ifdef PNG_sBIT_SUPPORTED
/* The sBIT chunk specifies the number of significant high-order bits
* in the pixel data. Values are in the range [1, bit_depth], and are
* only specified for the channels in the pixel data. The contents of
* the low-order bits is not specified. Data is valid if
* (valid & PNG_INFO_sBIT) is non-zero.
*/
png_color_8 sig_bit; /* significant bits in color channels */
#endif
#if defined(PNG_tRNS_SUPPORTED) || defined(PNG_READ_EXPAND_SUPPORTED) || \
defined(PNG_READ_BACKGROUND_SUPPORTED)
/* The tRNS chunk supplies transparency data for paletted images and
* other image types that don't need a full alpha channel. There are
* "num_trans" transparency values for a paletted image, stored in the
* same order as the palette colors, starting from index 0. Values
* for the data are in the range [0, 255], ranging from fully transparent
* to fully opaque, respectively. For non-paletted images, there is a
* single color specified that should be treated as fully transparent.
* Data is valid if (valid & PNG_INFO_tRNS) is non-zero.
*/
png_bytep trans_alpha; /* alpha values for paletted image */
png_color_16 trans_color; /* transparent color for non-palette image */
#endif
#if defined(PNG_bKGD_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
/* The bKGD chunk gives the suggested image background color if the
* display program does not have its own background color and the image
* is needs to composited onto a background before display. The colors
* in "background" are normally in the same color space/depth as the
* pixel data. Data is valid if (valid & PNG_INFO_bKGD) is non-zero.
*/
png_color_16 background;
#endif
#ifdef PNG_oFFs_SUPPORTED
/* The oFFs chunk gives the offset in "offset_unit_type" units rightwards
* and downwards from the top-left corner of the display, page, or other
* application-specific co-ordinate space. See the PNG_OFFSET_ defines
* below for the unit types. Valid if (valid & PNG_INFO_oFFs) non-zero.
*/
png_int_32 x_offset; /* x offset on page */
png_int_32 y_offset; /* y offset on page */
png_byte offset_unit_type; /* offset units type */
#endif
#ifdef PNG_pHYs_SUPPORTED
/* The pHYs chunk gives the physical pixel density of the image for
* display or printing in "phys_unit_type" units (see PNG_RESOLUTION_
* defines below). Data is valid if (valid & PNG_INFO_pHYs) is non-zero.
*/
png_uint_32 x_pixels_per_unit; /* horizontal pixel density */
png_uint_32 y_pixels_per_unit; /* vertical pixel density */
png_byte phys_unit_type; /* resolution type (see PNG_RESOLUTION_ below) */
#endif
#ifdef PNG_eXIf_SUPPORTED
int num_exif; /* Added at libpng-1.6.31 */
png_bytep exif;
# ifdef PNG_READ_eXIf_SUPPORTED
png_bytep eXIf_buf; /* Added at libpng-1.6.32 */
# endif
#endif
#ifdef PNG_hIST_SUPPORTED
/* The hIST chunk contains the relative frequency or importance of the
* various palette entries, so that a viewer can intelligently select a
* reduced-color palette, if required. Data is an array of "num_palette"
* values in the range [0,65535]. Data valid if (valid & PNG_INFO_hIST)
* is non-zero.
*/
png_uint_16p hist;
#endif
#ifdef PNG_pCAL_SUPPORTED
/* The pCAL chunk describes a transformation between the stored pixel
* values and original physical data values used to create the image.
* The integer range [0, 2^bit_depth - 1] maps to the floating-point
* range given by [pcal_X0, pcal_X1], and are further transformed by a
* (possibly non-linear) transformation function given by "pcal_type"
* and "pcal_params" into "pcal_units". Please see the PNG_EQUATION_
* defines below, and the PNG-Group's PNG extensions document for a
* complete description of the transformations and how they should be
* implemented, and for a description of the ASCII parameter strings.
* Data values are valid if (valid & PNG_INFO_pCAL) non-zero.
*/
png_charp pcal_purpose; /* pCAL chunk description string */
png_int_32 pcal_X0; /* minimum value */
png_int_32 pcal_X1; /* maximum value */
png_charp pcal_units; /* Latin-1 string giving physical units */
png_charpp pcal_params; /* ASCII strings containing parameter values */
png_byte pcal_type; /* equation type (see PNG_EQUATION_ below) */
png_byte pcal_nparams; /* number of parameters given in pcal_params */
#endif
/* New members added in libpng-1.0.6 */
png_uint_32 free_me; /* flags items libpng is responsible for freeing */
#ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
/* Storage for unknown chunks that the library doesn't recognize. */
png_unknown_chunkp unknown_chunks;
/* The type of this field is limited by the type of
* png_struct::user_chunk_cache_max, else overflow can occur.
*/
int unknown_chunks_num;
#endif
#ifdef PNG_sPLT_SUPPORTED
/* Data on sPLT chunks (there may be more than one). */
png_sPLT_tp splt_palettes;
int splt_palettes_num; /* Match type returned by png_get API */
#endif
#ifdef PNG_sCAL_SUPPORTED
/* The sCAL chunk describes the actual physical dimensions of the
* subject matter of the graphic. The chunk contains a unit specification
* a byte value, and two ASCII strings representing floating-point
* values. The values are width and height corresponding to one pixel
* in the image. Data values are valid if (valid & PNG_INFO_sCAL) is
* non-zero.
*/
png_byte scal_unit; /* unit of physical scale */
png_charp scal_s_width; /* string containing height */
png_charp scal_s_height; /* string containing width */
#endif
#ifdef PNG_INFO_IMAGE_SUPPORTED
/* Memory has been allocated if (valid & PNG_ALLOCATED_INFO_ROWS)
non-zero */
/* Data valid if (valid & PNG_INFO_IDAT) non-zero */
png_bytepp row_pointers; /* the image bits */
#endif
};
#endif /* PNGINFO_H */