1
  2/* pnginfo.h - header file for PNG reference library
  3 *
  4 * Last changed in libpng 1.6.1 [March 28, 2013]
  5 * Copyright (c) 1998-2002,2004,2006-2013 Glenn Randers-Pehrson
  6 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  7 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  8 *
  9 * This code is released under the libpng license.
 10 * For conditions of distribution and use, see the disclaimer
 11 * and license in png.h
 12 */
 13
 14 /* png_info is a structure that holds the information in a PNG file so
 15 * that the application can find out the characteristics of the image.
 16 * If you are reading the file, this structure will tell you what is
 17 * in the PNG file.  If you are writing the file, fill in the information
 18 * you want to put into the PNG file, using png_set_*() functions, then
 19 * call png_write_info().
 20 *
 21 * The names chosen should be very close to the PNG specification, so
 22 * consult that document for information about the meaning of each field.
 23 *
 24 * With libpng < 0.95, it was only possible to directly set and read the
 25 * the values in the png_info_struct, which meant that the contents and
 26 * order of the values had to remain fixed.  With libpng 0.95 and later,
 27 * however, there are now functions that abstract the contents of
 28 * png_info_struct from the application, so this makes it easier to use
 29 * libpng with dynamic libraries, and even makes it possible to use
 30 * libraries that don't have all of the libpng ancillary chunk-handing
 31 * functionality.  In libpng-1.5.0 this was moved into a separate private
 32 * file that is not visible to applications.
 33 *
 34 * The following members may have allocated storage attached that should be
 35 * cleaned up before the structure is discarded: palette, trans, text,
 36 * pcal_purpose, pcal_units, pcal_params, hist, iccp_name, iccp_profile,
 37 * splt_palettes, scal_unit, row_pointers, and unknowns.   By default, these
 38 * are automatically freed when the info structure is deallocated, if they were
 39 * allocated internally by libpng.  This behavior can be changed by means
 40 * of the png_data_freer() function.
 41 *
 42 * More allocation details: all the chunk-reading functions that
 43 * change these members go through the corresponding png_set_*
 44 * functions.  A function to clear these members is available: see
 45 * png_free_data().  The png_set_* functions do not depend on being
 46 * able to point info structure members to any of the storage they are
 47 * passed (they make their own copies), EXCEPT that the png_set_text
 48 * functions use the same storage passed to them in the text_ptr or
 49 * itxt_ptr structure argument, and the png_set_rows and png_set_unknowns
 50 * functions do not make their own copies.
 51 */
 52#ifndef PNGINFO_H
 53#define PNGINFO_H
 54
 55struct png_info_def
 56{
 57   /* The following are necessary for every PNG file */
 58   png_uint_32 width;  /* width of image in pixels (from IHDR) */
 59   png_uint_32 height; /* height of image in pixels (from IHDR) */
 60   png_uint_32 valid;  /* valid chunk data (see PNG_INFO_ below) */
 61   png_size_t rowbytes; /* bytes needed to hold an untransformed row */
 62   png_colorp palette;      /* array of color values (valid & PNG_INFO_PLTE) */
 63   png_uint_16 num_palette; /* number of color entries in "palette" (PLTE) */
 64   png_uint_16 num_trans;   /* number of transparent palette color (tRNS) */
 65   png_byte bit_depth;      /* 1, 2, 4, 8, or 16 bits/channel (from IHDR) */
 66   png_byte color_type;     /* see PNG_COLOR_TYPE_ below (from IHDR) */
 67   /* The following three should have been named *_method not *_type */
 68   png_byte compression_type; /* must be PNG_COMPRESSION_TYPE_BASE (IHDR) */
 69   png_byte filter_type;    /* must be PNG_FILTER_TYPE_BASE (from IHDR) */
 70   png_byte interlace_type; /* One of PNG_INTERLACE_NONE, PNG_INTERLACE_ADAM7 */
 71
 72   /* The following are set by png_set_IHDR, called from the application on
 73    * write, but the are never actually used by the write code.
 74    */
 75   png_byte channels;       /* number of data channels per pixel (1, 2, 3, 4) */
 76   png_byte pixel_depth;    /* number of bits per pixel */
 77   png_byte spare_byte;     /* to align the data, and for future use */
 78
 79#ifdef PNG_READ_SUPPORTED
 80   /* This is never set during write */
 81   png_byte signature[8];   /* magic bytes read by libpng from start of file */
 82#endif
 83
 84   /* The rest of the data is optional.  If you are reading, check the
 85    * valid field to see if the information in these are valid.  If you
 86    * are writing, set the valid field to those chunks you want written,
 87    * and initialize the appropriate fields below.
 88    */
 89
 90#if defined(PNG_COLORSPACE_SUPPORTED) || defined(PNG_GAMMA_SUPPORTED)
 91   /* png_colorspace only contains 'flags' if neither GAMMA or COLORSPACE are
 92    * defined.  When COLORSPACE is switched on all the colorspace-defining
 93    * chunks should be enabled, when GAMMA is switched on all the gamma-defining
 94    * chunks should be enabled.  If this is not done it becomes possible to read
 95    * inconsistent PNG files and assign a probably incorrect interpretation to
 96    * the information.  (In other words, by carefully choosing which chunks to
 97    * recognize the system configuration can select an interpretation for PNG
 98    * files containing ambiguous data and this will result in inconsistent
 99    * behavior between different libpng builds!)
100    */
101   png_colorspace colorspace;
102#endif
103
104#ifdef PNG_iCCP_SUPPORTED
105   /* iCCP chunk data. */
106   png_charp iccp_name;     /* profile name */
107   png_bytep iccp_profile;  /* International Color Consortium profile data */
108   png_uint_32 iccp_proflen;  /* ICC profile data length */
109#endif
110
111#ifdef PNG_TEXT_SUPPORTED
112   /* The tEXt, and zTXt chunks contain human-readable textual data in
113    * uncompressed, compressed, and optionally compressed forms, respectively.
114    * The data in "text" is an array of pointers to uncompressed,
115    * null-terminated C strings. Each chunk has a keyword that describes the
116    * textual data contained in that chunk.  Keywords are not required to be
117    * unique, and the text string may be empty.  Any number of text chunks may
118    * be in an image.
119    */
120   int num_text; /* number of comments read or comments to write */
121   int max_text; /* current size of text array */
122   png_textp text; /* array of comments read or comments to write */
123#endif /* TEXT */
124
125#ifdef PNG_tIME_SUPPORTED
126   /* The tIME chunk holds the last time the displayed image data was
127    * modified.  See the png_time struct for the contents of this struct.
128    */
129   png_time mod_time;
130#endif
131
132#ifdef PNG_sBIT_SUPPORTED
133   /* The sBIT chunk specifies the number of significant high-order bits
134    * in the pixel data.  Values are in the range [1, bit_depth], and are
135    * only specified for the channels in the pixel data.  The contents of
136    * the low-order bits is not specified.  Data is valid if
137    * (valid & PNG_INFO_sBIT) is non-zero.
138    */
139   png_color_8 sig_bit; /* significant bits in color channels */
140#endif
141
142#if defined(PNG_tRNS_SUPPORTED) || defined(PNG_READ_EXPAND_SUPPORTED) || \
143defined(PNG_READ_BACKGROUND_SUPPORTED)
144   /* The tRNS chunk supplies transparency data for paletted images and
145    * other image types that don't need a full alpha channel.  There are
146    * "num_trans" transparency values for a paletted image, stored in the
147    * same order as the palette colors, starting from index 0.  Values
148    * for the data are in the range [0, 255], ranging from fully transparent
149    * to fully opaque, respectively.  For non-paletted images, there is a
150    * single color specified that should be treated as fully transparent.
151    * Data is valid if (valid & PNG_INFO_tRNS) is non-zero.
152    */
153   png_bytep trans_alpha;    /* alpha values for paletted image */
154   png_color_16 trans_color; /* transparent color for non-palette image */
155#endif
156
157#if defined(PNG_bKGD_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
158   /* The bKGD chunk gives the suggested image background color if the
159    * display program does not have its own background color and the image
160    * is needs to composited onto a background before display.  The colors
161    * in "background" are normally in the same color space/depth as the
162    * pixel data.  Data is valid if (valid & PNG_INFO_bKGD) is non-zero.
163    */
164   png_color_16 background;
165#endif
166
167#ifdef PNG_oFFs_SUPPORTED
168   /* The oFFs chunk gives the offset in "offset_unit_type" units rightwards
169    * and downwards from the top-left corner of the display, page, or other
170    * application-specific co-ordinate space.  See the PNG_OFFSET_ defines
171    * below for the unit types.  Valid if (valid & PNG_INFO_oFFs) non-zero.
172    */
173   png_int_32 x_offset; /* x offset on page */
174   png_int_32 y_offset; /* y offset on page */
175   png_byte offset_unit_type; /* offset units type */
176#endif
177
178#ifdef PNG_pHYs_SUPPORTED
179   /* The pHYs chunk gives the physical pixel density of the image for
180    * display or printing in "phys_unit_type" units (see PNG_RESOLUTION_
181    * defines below).  Data is valid if (valid & PNG_INFO_pHYs) is non-zero.
182    */
183   png_uint_32 x_pixels_per_unit; /* horizontal pixel density */
184   png_uint_32 y_pixels_per_unit; /* vertical pixel density */
185   png_byte phys_unit_type; /* resolution type (see PNG_RESOLUTION_ below) */
186#endif
187
188#ifdef PNG_eXIf_SUPPORTED
189   int num_exif;  /* Added at libpng-1.6.31 */
190   png_bytep exif;
191# ifdef PNG_READ_eXIf_SUPPORTED
192   png_bytep eXIf_buf;  /* Added at libpng-1.6.32 */
193# endif
194#endif
195
196#ifdef PNG_hIST_SUPPORTED
197   /* The hIST chunk contains the relative frequency or importance of the
198    * various palette entries, so that a viewer can intelligently select a
199    * reduced-color palette, if required.  Data is an array of "num_palette"
200    * values in the range [0,65535]. Data valid if (valid & PNG_INFO_hIST)
201    * is non-zero.
202    */
203   png_uint_16p hist;
204#endif
205
206#ifdef PNG_pCAL_SUPPORTED
207   /* The pCAL chunk describes a transformation between the stored pixel
208    * values and original physical data values used to create the image.
209    * The integer range [0, 2^bit_depth - 1] maps to the floating-point
210    * range given by [pcal_X0, pcal_X1], and are further transformed by a
211    * (possibly non-linear) transformation function given by "pcal_type"
212    * and "pcal_params" into "pcal_units".  Please see the PNG_EQUATION_
213    * defines below, and the PNG-Group's PNG extensions document for a
214    * complete description of the transformations and how they should be
215    * implemented, and for a description of the ASCII parameter strings.
216    * Data values are valid if (valid & PNG_INFO_pCAL) non-zero.
217    */
218   png_charp pcal_purpose;  /* pCAL chunk description string */
219   png_int_32 pcal_X0;      /* minimum value */
220   png_int_32 pcal_X1;      /* maximum value */
221   png_charp pcal_units;    /* Latin-1 string giving physical units */
222   png_charpp pcal_params;  /* ASCII strings containing parameter values */
223   png_byte pcal_type;      /* equation type (see PNG_EQUATION_ below) */
224   png_byte pcal_nparams;   /* number of parameters given in pcal_params */
225#endif
226
227/* New members added in libpng-1.0.6 */
228   png_uint_32 free_me;     /* flags items libpng is responsible for freeing */
229
230#ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
231   /* Storage for unknown chunks that the library doesn't recognize. */
232   png_unknown_chunkp unknown_chunks;
233
234   /* The type of this field is limited by the type of
235    * png_struct::user_chunk_cache_max, else overflow can occur.
236    */
237   int                unknown_chunks_num;
238#endif
239
240#ifdef PNG_sPLT_SUPPORTED
241   /* Data on sPLT chunks (there may be more than one). */
242   png_sPLT_tp splt_palettes;
243   int         splt_palettes_num; /* Match type returned by png_get API */
244#endif
245
246#ifdef PNG_sCAL_SUPPORTED
247   /* The sCAL chunk describes the actual physical dimensions of the
248    * subject matter of the graphic.  The chunk contains a unit specification
249    * a byte value, and two ASCII strings representing floating-point
250    * values.  The values are width and height corresponsing to one pixel
251    * in the image.  Data values are valid if (valid & PNG_INFO_sCAL) is
252    * non-zero.
253    */
254   png_byte scal_unit;         /* unit of physical scale */
255   png_charp scal_s_width;     /* string containing height */
256   png_charp scal_s_height;    /* string containing width */
257#endif
258
259#ifdef PNG_INFO_IMAGE_SUPPORTED
260   /* Memory has been allocated if (valid & PNG_ALLOCATED_INFO_ROWS)
261      non-zero */
262   /* Data valid if (valid & PNG_INFO_IDAT) non-zero */
263   png_bytepp row_pointers;        /* the image bits */
264#endif
265
266};
267#endif /* PNGINFO_H */