Manual Reference Pages - RLE_HDR (3)
rle_hdr - Structure for communication with RLE functions.
This data structure provides communication to and between all the
file routines. It describes the parameters of the image being saved
or read, and contains some variables describing file state that are
private to the routines. The public components are described below.
typedef unsigned char rle_pixel;
typedef unsigned short rle_map;
int ncolors, /* Number of colors being saved */
*bg_color,/* Background color array */
alpha, /* if != 0, save alpha channel (color -1) */
/* alpha channel background is always 0 */
background,/* if = 0, no background processing */
/* if = 1 or 2, save only non-bg pixels */
/* If 2, set clear-to-bg flag in file */
xmin, /* Min X bound of saved raster */
xmax, /* Max X bound */
ymin, /* Min Y bound */
ymax, /* Max Y bound */
ncmap, /* number of color channels in color map */
/* if = 0, color map is not saved */
cmaplen; /* Log2 of the number of entries in */
/* each channel of the color map */
rle_map *cmap; /* pointer to color map, stored as 16-bit */
/* words, with values left justified */
char **comments;/* Pointer to array of pointers */
/* to comment strings. */
FILE * rle_file; /* I/O to this file */
* Bit map of channels to read/save. Indexed by (channel mod 256).
A global variable,
rle_dflt_hdr, is available, conveniently initialized with default values.
The number of colors (exclusive of the alpha channel) in the image.
This is one greater than the largest channel index (i.e.,
ncolors would be 3 if channels 0, 1, and 2 were saved, or if
only channel 2 were saved.)
A pointer to an array of ncolors integers, defines the
background color (if used). The background alpha value is always 0,
so is not included in the bg_color array.
If non-zero, an alpha channel is present as channel -1. This
should always be 0 or 1. Rle_get_setup and rle_put_setup
enforce this constraint. The alpha channel will only be actually read
or written if the corresponding bit in bits is also set.
Controls whether background color processing is done. If 0, no
background processing is done at all (and bg_color is ignored).
If 1 or 2, then runs of 3 or more pixels in the background color are
not saved at all. If 2, then these runs will be restored by
rle_getrow; if 1, they will not (this can lead to some strange
xmin, xmax, ymin, ymax |
The bounds of the image. All pixels from xmin to xmax,
inclusive, in rows numbered from ymin to ymax, inclusive,
will be saved. Thus the dimensions of the image are
(xmax - xmin + 1) × (ymax - ymin + 1)
ncmap, cmaplen |
The size of the saved colormap (if any). The color map will have
ncmap channels, each 2^cmaplen long. If ncmap is
zero, no color map is present.
A pointer to colormap data, if present. The data is stored in
"channel major" order, so that all the values for channel 0 precede
all the values for channel 1, etc. Each individual value is
left-justified in 16 bits (i.e., the range of values is 0-65535).
A pointer to picture comment data, if present. Use the functions
to manipulate this field.
The standard I/O FILE pointer for the file containing this
A bitmap that selects the channels that are actually written to/read
from the file. The macros below are used to modify this bitmap.
RLE_BIT will retrieve the state of one of the bits in the
RLE_CLR_BIT set and clear bits in the
bits map. The predefined symbols
RLE_ALPHA, or an integer value from -1 to 254
may be used in these macros.
Spencer W. Thomas, Todd Fuqua
Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.