src/png/pnginfo.h

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