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 */
270