src/png/pnginfo.h

   1
   2 /* pnginfo.h - header file for PNG reference library
   3  *
   4  * Copyright (c) 1998-2011 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 1.5.0 [January 6, 2011]
   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 is informational only on read, and not used on writes. */
  74    png_byte channels;       /* number of data channels per pixel (1, 2, 3, 4) */
  75    png_byte pixel_depth;    /* number of bits per pixel */
  76    png_byte spare_byte;     /* to align the data, and for future use */
  77    png_byte signature[8];   /* magic bytes read by libpng from start of file */
  78
  79    /* The rest of the data is optional.  If you are reading, check the
  80     * valid field to see if the information in these are valid.  If you
  81     * are writing, set the valid field to those chunks you want written,
  82     * and initialize the appropriate fields below.
  83     */
  84
  85 #if defined(PNG_gAMA_SUPPORTED)
  86    /* The gAMA chunk describes the gamma characteristics of the system
  87     * on which the image was created, normally in the range [1.0, 2.5].
  88     * Data is valid if (valid & PNG_INFO_gAMA) is non-zero.
  89     */
  90    png_fixed_point gamma;
  91 #endif
  92
  93 #ifdef PNG_sRGB_SUPPORTED
  94     /* GR-P, 0.96a */
  95     /* Data valid if (valid & PNG_INFO_sRGB) non-zero. */
  96    png_byte srgb_intent; /* sRGB rendering intent [0, 1, 2, or 3] */
  97 #endif
  98
  99 #ifdef PNG_TEXT_SUPPORTED
 100    /* The tEXt, and zTXt chunks contain human-readable textual data in
 101     * uncompressed, compressed, and optionally compressed forms, respectively.
 102     * The data in "text" is an array of pointers to uncompressed,
 103     * null-terminated C strings. Each chunk has a keyword that describes the
 104     * textual data contained in that chunk.  Keywords are not required to be
 105     * unique, and the text string may be empty.  Any number of text chunks may
 106     * be in an image.
 107     */
 108    int num_text; /* number of comments read or comments to write */
 109    int max_text; /* current size of text array */
 110    png_textp text; /* array of comments read or comments to write */
 111 #endif /* PNG_TEXT_SUPPORTED */
 112
 113 #ifdef PNG_tIME_SUPPORTED
 114    /* The tIME chunk holds the last time the displayed image data was
 115     * modified.  See the png_time struct for the contents of this struct.
 116     */
 117    png_time mod_time;
 118 #endif
 119
 120 #ifdef PNG_sBIT_SUPPORTED
 121    /* The sBIT chunk specifies the number of significant high-order bits
 122     * in the pixel data.  Values are in the range [1, bit_depth], and are
 123     * only specified for the channels in the pixel data.  The contents of
 124     * the low-order bits is not specified.  Data is valid if
 125     * (valid & PNG_INFO_sBIT) is non-zero.
 126     */
 127    png_color_8 sig_bit; /* significant bits in color channels */
 128 #endif
 129
 130 #if defined(PNG_tRNS_SUPPORTED) || defined(PNG_READ_EXPAND_SUPPORTED) || \
 131 defined(PNG_READ_BACKGROUND_SUPPORTED)
 132    /* The tRNS chunk supplies transparency data for paletted images and
 133     * other image types that don't need a full alpha channel.  There are
 134     * "num_trans" transparency values for a paletted image, stored in the
 135     * same order as the palette colors, starting from index 0.  Values
 136     * for the data are in the range [0, 255], ranging from fully transparent
 137     * to fully opaque, respectively.  For non-paletted images, there is a
 138     * single color specified that should be treated as fully transparent.
 139     * Data is valid if (valid & PNG_INFO_tRNS) is non-zero.
 140     */
 141    png_bytep trans_alpha;    /* alpha values for paletted image */
 142    png_color_16 trans_color; /* transparent color for non-palette image */
 143 #endif
 144
 145 #if defined(PNG_bKGD_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
 146    /* The bKGD chunk gives the suggested image background color if the
 147     * display program does not have its own background color and the image
 148     * is needs to composited onto a background before display.  The colors
 149     * in "background" are normally in the same color space/depth as the
 150     * pixel data.  Data is valid if (valid & PNG_INFO_bKGD) is non-zero.
 151     */
 152    png_color_16 background;
 153 #endif
 154
 155 #ifdef PNG_oFFs_SUPPORTED
 156    /* The oFFs chunk gives the offset in "offset_unit_type" units rightwards
 157     * and downwards from the top-left corner of the display, page, or other
 158     * application-specific co-ordinate space.  See the PNG_OFFSET_ defines
 159     * below for the unit types.  Valid if (valid & PNG_INFO_oFFs) non-zero.
 160     */
 161    png_int_32 x_offset; /* x offset on page */
 162    png_int_32 y_offset; /* y offset on page */
 163    png_byte offset_unit_type; /* offset units type */
 164 #endif
 165
 166 #ifdef PNG_pHYs_SUPPORTED
 167    /* The pHYs chunk gives the physical pixel density of the image for
 168     * display or printing in "phys_unit_type" units (see PNG_RESOLUTION_
 169     * defines below).  Data is valid if (valid & PNG_INFO_pHYs) is non-zero.
 170     */
 171    png_uint_32 x_pixels_per_unit; /* horizontal pixel density */
 172    png_uint_32 y_pixels_per_unit; /* vertical pixel density */
 173    png_byte phys_unit_type; /* resolution type (see PNG_RESOLUTION_ below) */
 174 #endif
 175
 176 #ifdef PNG_hIST_SUPPORTED
 177    /* The hIST chunk contains the relative frequency or importance of the
 178     * various palette entries, so that a viewer can intelligently select a
 179     * reduced-color palette, if required.  Data is an array of "num_palette"
 180     * values in the range [0,65535]. Data valid if (valid & PNG_INFO_hIST)
 181     * is non-zero.
 182     */
 183    png_uint_16p hist;
 184 #endif
 185
 186 #ifdef PNG_cHRM_SUPPORTED
 187    /* The cHRM chunk describes the CIE color characteristics of the monitor
 188     * on which the PNG was created.  This data allows the viewer to do gamut
 189     * mapping of the input image to ensure that the viewer sees the same
 190     * colors in the image as the creator.  Values are in the range
 191     * [0.0, 0.8].  Data valid if (valid & PNG_INFO_cHRM) non-zero.
 192     */
 193    png_fixed_point x_white;
 194    png_fixed_point y_white;
 195    png_fixed_point x_red;
 196    png_fixed_point y_red;
 197    png_fixed_point x_green;
 198    png_fixed_point y_green;
 199    png_fixed_point x_blue;
 200    png_fixed_point y_blue;
 201 #endif
 202
 203 #ifdef PNG_pCAL_SUPPORTED
 204    /* The pCAL chunk describes a transformation between the stored pixel
 205     * values and original physical data values used to create the image.
 206     * The integer range [0, 2^bit_depth - 1] maps to the floating-point
 207     * range given by [pcal_X0, pcal_X1], and are further transformed by a
 208     * (possibly non-linear) transformation function given by "pcal_type"
 209     * and "pcal_params" into "pcal_units".  Please see the PNG_EQUATION_
 210     * defines below, and the PNG-Group's PNG extensions document for a
 211     * complete description of the transformations and how they should be
 212     * implemented, and for a description of the ASCII parameter strings.
 213     * Data values are valid if (valid & PNG_INFO_pCAL) non-zero.
 214     */
 215    png_charp pcal_purpose;  /* pCAL chunk description string */
 216    png_int_32 pcal_X0;      /* minimum value */
 217    png_int_32 pcal_X1;      /* maximum value */
 218    png_charp pcal_units;    /* Latin-1 string giving physical units */
 219    png_charpp pcal_params;  /* ASCII strings containing parameter values */
 220    png_byte pcal_type;      /* equation type (see PNG_EQUATION_ below) */
 221    png_byte pcal_nparams;   /* number of parameters given in pcal_params */
 222 #endif
 223
 224 /* New members added in libpng-1.0.6 */
 225    png_uint_32 free_me;     /* flags items libpng is responsible for freeing */
 226
 227 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED) || \
 228  defined(PNG_HANDLE_AS_UNKNOWN_SUPPORTED)
 229    /* Storage for unknown chunks that the library doesn't recognize. */
 230    png_unknown_chunkp unknown_chunks;
 231    int unknown_chunks_num;
 232 #endif
 233
 234 #ifdef PNG_iCCP_SUPPORTED
 235    /* iCCP chunk data. */
 236    png_charp iccp_name;     /* profile name */
 237    png_bytep iccp_profile;  /* International Color Consortium profile data */
 238    png_uint_32 iccp_proflen;  /* ICC profile data length */
 239    png_byte iccp_compression; /* Always zero */
 240 #endif
 241
 242 #ifdef PNG_sPLT_SUPPORTED
 243    /* Data on sPLT chunks (there may be more than one). */
 244    png_sPLT_tp splt_palettes;
 245    png_uint_32 splt_palettes_num;
 246 #endif
 247
 248 #ifdef PNG_sCAL_SUPPORTED
 249    /* The sCAL chunk describes the actual physical dimensions of the
 250     * subject matter of the graphic.  The chunk contains a unit specification
 251     * a byte value, and two ASCII strings representing floating-point
 252     * values.  The values are width and height corresponsing to one pixel
 253     * in the image.  Data values are valid if (valid & PNG_INFO_sCAL) is
 254     * non-zero.
 255     */
 256    png_byte scal_unit;         /* unit of physical scale */
 257    png_charp scal_s_width;     /* string containing height */
 258    png_charp scal_s_height;    /* string containing width */
 259 #endif
 260
 261 #ifdef PNG_INFO_IMAGE_SUPPORTED
 262    /* Memory has been allocated if (valid & PNG_ALLOCATED_INFO_ROWS)
 263       non-zero */
 264    /* Data valid if (valid & PNG_INFO_IDAT) non-zero */
 265    png_bytepp row_pointers;        /* the image bits */
 266 #endif
 267
 268 };
 269 #endif /* PNGINFO_H */