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 */ 261