302 lines
15 KiB
C
302 lines
15 KiB
C
/* png_info is a structure that holds the information in a PNG file so
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* that the application can find out the characteristics of the image.
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* If you are reading the file, this structure will tell you what is
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* in the PNG file. If you are writing the file, fill in the information
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* you want to put into the PNG file, then call png_write_info().
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* The names chosen should be very close to the PNG specification, so
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* consult that document for information about the meaning of each field.
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*
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* With libpng < 0.95, it was only possible to directly set and read the
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* the values in the png_info_struct, which meant that the contents and
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* order of the values had to remain fixed. With libpng 0.95 and later,
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* however, there are now functions that abstract the contents of
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* png_info_struct from the application, so this makes it easier to use
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* libpng with dynamic libraries, and even makes it possible to use
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* libraries that don't have all of the libpng ancillary chunk-handing
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* functionality.
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*
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* In any case, the order of the parameters in png_info_struct should NOT
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* be changed for as long as possible to keep compatibility with applications
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* that use the old direct-access method with png_info_struct.
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*
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* The following members may have allocated storage attached that should be
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* cleaned up before the structure is discarded: palette, trans, text,
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* pcal_purpose, pcal_units, pcal_params, hist, iccp_name, iccp_profile,
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* splt_palettes, scal_unit, row_pointers, and unknowns. By default, these
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* are automatically freed when the info structure is deallocated, if they were
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* allocated internally by libpng. This behavior can be changed by means
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* of the png_data_freer() function.
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*
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* More allocation details: all the chunk-reading functions that
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* change these members go through the corresponding png_set_*
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* functions. A function to clear these members is available: see
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* png_free_data(). The png_set_* functions do not depend on being
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* able to point info structure members to any of the storage they are
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* passed (they make their own copies), EXCEPT that the png_set_text
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* functions use the same storage passed to them in the text_ptr or
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* itxt_ptr structure argument, and the png_set_rows and png_set_unknowns
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* functions do not make their own copies.
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*/
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typedef struct png_info_struct
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{
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/* the following are necessary for every PNG file */
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png_uint_32 width PNG_DEPSTRUCT; /* width of image in pixels (from IHDR) */
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png_uint_32 height PNG_DEPSTRUCT; /* height of image in pixels (from IHDR) */
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png_uint_32 valid PNG_DEPSTRUCT; /* valid chunk data (see PNG_INFO_
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below) */
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png_size_t rowbytes PNG_DEPSTRUCT; /* bytes needed to hold an untransformed
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row */
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png_colorp palette PNG_DEPSTRUCT; /* array of color values
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(valid & PNG_INFO_PLTE) */
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png_uint_16 num_palette PNG_DEPSTRUCT; /* number of color entries in
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"palette" (PLTE) */
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png_uint_16 num_trans PNG_DEPSTRUCT; /* number of transparent palette
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color (tRNS) */
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png_byte bit_depth PNG_DEPSTRUCT; /* 1, 2, 4, 8, or 16 bits/channel
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(from IHDR) */
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png_byte color_type PNG_DEPSTRUCT; /* see PNG_COLOR_TYPE_ below
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(from IHDR) */
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/* The following three should have been named *_method not *_type */
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png_byte compression_type PNG_DEPSTRUCT; /* must be
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PNG_COMPRESSION_TYPE_BASE (IHDR) */
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png_byte filter_type PNG_DEPSTRUCT; /* must be PNG_FILTER_TYPE_BASE
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(from IHDR) */
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png_byte interlace_type PNG_DEPSTRUCT; /* One of PNG_INTERLACE_NONE,
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PNG_INTERLACE_ADAM7 */
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/* The following is informational only on read, and not used on writes. */
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png_byte channels PNG_DEPSTRUCT; /* number of data channels per
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pixel (1, 2, 3, 4) */
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png_byte pixel_depth PNG_DEPSTRUCT; /* number of bits per pixel */
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png_byte spare_byte PNG_DEPSTRUCT; /* to align the data, and for
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future use */
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png_byte signature[8] PNG_DEPSTRUCT; /* magic bytes read by libpng
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from start of file */
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/* The rest of the data is optional. If you are reading, check the
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* valid field to see if the information in these are valid. If you
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* are writing, set the valid field to those chunks you want written,
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* and initialize the appropriate fields below.
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*/
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#if defined(PNG_gAMA_SUPPORTED) && defined(PNG_FLOATING_POINT_SUPPORTED)
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/* The gAMA chunk describes the gamma characteristics of the system
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* on which the image was created, normally in the range [1.0, 2.5].
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* Data is valid if (valid & PNG_INFO_gAMA) is non-zero.
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*/
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float gamma PNG_DEPSTRUCT; /* gamma value of image,
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if (valid & PNG_INFO_gAMA) */
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#endif
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#ifdef PNG_sRGB_SUPPORTED
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/* GR-P, 0.96a */
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/* Data valid if (valid & PNG_INFO_sRGB) non-zero. */
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png_byte srgb_intent PNG_DEPSTRUCT; /* sRGB rendering intent
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[0, 1, 2, or 3] */
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#endif
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#ifdef PNG_TEXT_SUPPORTED
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/* The tEXt, and zTXt chunks contain human-readable textual data in
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* uncompressed, compressed, and optionally compressed forms, respectively.
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* The data in "text" is an array of pointers to uncompressed,
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* null-terminated C strings. Each chunk has a keyword that describes the
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* textual data contained in that chunk. Keywords are not required to be
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* unique, and the text string may be empty. Any number of text chunks may
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* be in an image.
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*/
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int num_text PNG_DEPSTRUCT; /* number of comments read/to write */
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int max_text PNG_DEPSTRUCT; /* current size of text array */
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png_textp text PNG_DEPSTRUCT; /* array of comments read/to write */
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#endif /* PNG_TEXT_SUPPORTED */
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#ifdef PNG_tIME_SUPPORTED
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/* The tIME chunk holds the last time the displayed image data was
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* modified. See the png_time struct for the contents of this struct.
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*/
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png_time mod_time PNG_DEPSTRUCT;
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#endif
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#ifdef PNG_sBIT_SUPPORTED
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/* The sBIT chunk specifies the number of significant high-order bits
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* in the pixel data. Values are in the range [1, bit_depth], and are
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* only specified for the channels in the pixel data. The contents of
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* the low-order bits is not specified. Data is valid if
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* (valid & PNG_INFO_sBIT) is non-zero.
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*/
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png_color_8 sig_bit PNG_DEPSTRUCT; /* significant bits in color channels */
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#endif
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#if defined(PNG_tRNS_SUPPORTED) || defined(PNG_READ_EXPAND_SUPPORTED) || \
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defined(PNG_READ_BACKGROUND_SUPPORTED)
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/* The tRNS chunk supplies transparency data for paletted images and
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* other image types that don't need a full alpha channel. There are
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* "num_trans" transparency values for a paletted image, stored in the
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* same order as the palette colors, starting from index 0. Values
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* for the data are in the range [0, 255], ranging from fully transparent
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* to fully opaque, respectively. For non-paletted images, there is a
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* single color specified that should be treated as fully transparent.
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* Data is valid if (valid & PNG_INFO_tRNS) is non-zero.
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*/
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png_bytep trans_alpha PNG_DEPSTRUCT; /* alpha values for paletted
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image */
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png_color_16 trans_color PNG_DEPSTRUCT; /* transparent color for
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non-palette image */
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#endif
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#if defined(PNG_bKGD_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
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/* The bKGD chunk gives the suggested image background color if the
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* display program does not have its own background color and the image
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* is needs to composited onto a background before display. The colors
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* in "background" are normally in the same color space/depth as the
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* pixel data. Data is valid if (valid & PNG_INFO_bKGD) is non-zero.
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*/
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png_color_16 background PNG_DEPSTRUCT;
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#endif
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#ifdef PNG_oFFs_SUPPORTED
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/* The oFFs chunk gives the offset in "offset_unit_type" units rightwards
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* and downwards from the top-left corner of the display, page, or other
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* application-specific co-ordinate space. See the PNG_OFFSET_ defines
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* below for the unit types. Valid if (valid & PNG_INFO_oFFs) non-zero.
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*/
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png_int_32 x_offset PNG_DEPSTRUCT; /* x offset on page */
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png_int_32 y_offset PNG_DEPSTRUCT; /* y offset on page */
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png_byte offset_unit_type PNG_DEPSTRUCT; /* offset units type */
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#endif
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#ifdef PNG_pHYs_SUPPORTED
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/* The pHYs chunk gives the physical pixel density of the image for
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* display or printing in "phys_unit_type" units (see PNG_RESOLUTION_
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* defines below). Data is valid if (valid & PNG_INFO_pHYs) is non-zero.
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*/
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png_uint_32 x_pixels_per_unit PNG_DEPSTRUCT; /* horizontal pixel density */
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png_uint_32 y_pixels_per_unit PNG_DEPSTRUCT; /* vertical pixel density */
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png_byte phys_unit_type PNG_DEPSTRUCT; /* resolution type (see
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PNG_RESOLUTION_ below) */
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#endif
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#ifdef PNG_hIST_SUPPORTED
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/* The hIST chunk contains the relative frequency or importance of the
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* various palette entries, so that a viewer can intelligently select a
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* reduced-color palette, if required. Data is an array of "num_palette"
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* values in the range [0,65535]. Data valid if (valid & PNG_INFO_hIST)
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* is non-zero.
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*/
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png_uint_16p hist PNG_DEPSTRUCT;
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#endif
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#ifdef PNG_cHRM_SUPPORTED
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/* The cHRM chunk describes the CIE color characteristics of the monitor
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* on which the PNG was created. This data allows the viewer to do gamut
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* mapping of the input image to ensure that the viewer sees the same
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* colors in the image as the creator. Values are in the range
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* [0.0, 0.8]. Data valid if (valid & PNG_INFO_cHRM) non-zero.
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*/
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#ifdef PNG_FLOATING_POINT_SUPPORTED
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float x_white PNG_DEPSTRUCT;
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float y_white PNG_DEPSTRUCT;
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float x_red PNG_DEPSTRUCT;
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float y_red PNG_DEPSTRUCT;
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float x_green PNG_DEPSTRUCT;
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float y_green PNG_DEPSTRUCT;
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float x_blue PNG_DEPSTRUCT;
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float y_blue PNG_DEPSTRUCT;
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#endif
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#endif
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#ifdef PNG_pCAL_SUPPORTED
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/* The pCAL chunk describes a transformation between the stored pixel
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* values and original physical data values used to create the image.
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* The integer range [0, 2^bit_depth - 1] maps to the floating-point
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* range given by [pcal_X0, pcal_X1], and are further transformed by a
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* (possibly non-linear) transformation function given by "pcal_type"
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* and "pcal_params" into "pcal_units". Please see the PNG_EQUATION_
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* defines below, and the PNG-Group's PNG extensions document for a
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* complete description of the transformations and how they should be
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* implemented, and for a description of the ASCII parameter strings.
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* Data values are valid if (valid & PNG_INFO_pCAL) non-zero.
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*/
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png_charp pcal_purpose PNG_DEPSTRUCT; /* pCAL chunk description string */
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png_int_32 pcal_X0 PNG_DEPSTRUCT; /* minimum value */
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png_int_32 pcal_X1 PNG_DEPSTRUCT; /* maximum value */
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png_charp pcal_units PNG_DEPSTRUCT; /* Latin-1 string giving physical
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units */
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png_charpp pcal_params PNG_DEPSTRUCT; /* ASCII strings containing
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parameter values */
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png_byte pcal_type PNG_DEPSTRUCT; /* equation type
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(see PNG_EQUATION_ below) */
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png_byte pcal_nparams PNG_DEPSTRUCT; /* number of parameters given
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in pcal_params */
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#endif
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/* New members added in libpng-1.0.6 */
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png_uint_32 free_me PNG_DEPSTRUCT; /* flags items libpng is
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responsible for freeing */
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#if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED) || \
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defined(PNG_HANDLE_AS_UNKNOWN_SUPPORTED)
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/* Storage for unknown chunks that the library doesn't recognize. */
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png_unknown_chunkp unknown_chunks PNG_DEPSTRUCT;
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png_size_t unknown_chunks_num PNG_DEPSTRUCT;
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#endif
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#ifdef PNG_iCCP_SUPPORTED
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/* iCCP chunk data. */
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png_charp iccp_name PNG_DEPSTRUCT; /* profile name */
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png_charp iccp_profile PNG_DEPSTRUCT; /* International Color Consortium
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profile data */
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/* Note to maintainer: should be png_bytep */
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png_uint_32 iccp_proflen PNG_DEPSTRUCT; /* ICC profile data length */
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png_byte iccp_compression PNG_DEPSTRUCT; /* Always zero */
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#endif
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#ifdef PNG_sPLT_SUPPORTED
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/* Data on sPLT chunks (there may be more than one). */
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png_sPLT_tp splt_palettes PNG_DEPSTRUCT;
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png_uint_32 splt_palettes_num PNG_DEPSTRUCT;
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#endif
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#ifdef PNG_sCAL_SUPPORTED
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/* The sCAL chunk describes the actual physical dimensions of the
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* subject matter of the graphic. The chunk contains a unit specification
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* a byte value, and two ASCII strings representing floating-point
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* values. The values are width and height corresponsing to one pixel
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* in the image. This external representation is converted to double
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* here. Data values are valid if (valid & PNG_INFO_sCAL) is non-zero.
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*/
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png_byte scal_unit PNG_DEPSTRUCT; /* unit of physical scale */
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#ifdef PNG_FLOATING_POINT_SUPPORTED
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double scal_pixel_width PNG_DEPSTRUCT; /* width of one pixel */
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double scal_pixel_height PNG_DEPSTRUCT; /* height of one pixel */
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#endif
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#ifdef PNG_FIXED_POINT_SUPPORTED
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png_charp scal_s_width PNG_DEPSTRUCT; /* string containing height */
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png_charp scal_s_height PNG_DEPSTRUCT; /* string containing width */
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#endif
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#endif
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#ifdef PNG_INFO_IMAGE_SUPPORTED
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/* Memory has been allocated if (valid & PNG_ALLOCATED_INFO_ROWS)
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non-zero */
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/* Data valid if (valid & PNG_INFO_IDAT) non-zero */
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png_bytepp row_pointers PNG_DEPSTRUCT; /* the image bits */
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#endif
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#if defined(PNG_FIXED_POINT_SUPPORTED) && defined(PNG_gAMA_SUPPORTED)
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png_fixed_point int_gamma PNG_DEPSTRUCT; /* gamma of image,
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if (valid & PNG_INFO_gAMA) */
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#endif
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#if defined(PNG_cHRM_SUPPORTED) && defined(PNG_FIXED_POINT_SUPPORTED)
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png_fixed_point int_x_white PNG_DEPSTRUCT;
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png_fixed_point int_y_white PNG_DEPSTRUCT;
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png_fixed_point int_x_red PNG_DEPSTRUCT;
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png_fixed_point int_y_red PNG_DEPSTRUCT;
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png_fixed_point int_x_green PNG_DEPSTRUCT;
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png_fixed_point int_y_green PNG_DEPSTRUCT;
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png_fixed_point int_x_blue PNG_DEPSTRUCT;
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png_fixed_point int_y_blue PNG_DEPSTRUCT;
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#endif
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} png_info;
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