term% cat index.txt MEMDRAW(2) System Calls Manual MEMDRAW(2)
NAME
Memimage, Memdata, Memdrawparam, memimageinit, wordaddr, byteaddr,
memimagemove, allocmemimage, allocmemimaged, readmemimage, creadmemim‐
age, writememimage, freememimage, memsetchan, loadmemimage, cloadmemim‐
age, unloadmemimage, memfillcolor, memarc, mempoly, memellipse, mem‐
fillpoly, memimageline, memimagedraw, drawclip, drawclipnorepl, mem‐
linebbox, memlineendsize, allocmemsubfont, openmemsubfont, freememsub‐
font, memsubfontwidth, getmemdefont, memimagestring, iprint, hwdraw -
drawing routines for memory-resident images
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <draw.h>
#include <memdraw.h>
typedef struct Memdata
{
ulong *base; /* allocated data pointer */
uchar *bdata; /* first byte of actual data; word-aligned */
int ref; /* number of Memimages using this data */
void* imref; /* last image that pointed at this */
int allocd; /* is this malloc'd? */
} Memdata;
enum {
Frepl = 1<<0, /* is replicated */
Fsimple = 1<<1, /* is 1x1 */
Fgrey = 1<<2, /* is grey */
Falpha = 1<<3, /* has explicit alpha */
Fcmap = 1<<4, /* has cmap channel */
Fbytes = 1<<5, /* has only 8-bit channels */
};
typedef struct Memimage
{
Rectangle r; /* rectangle in data area, local coords */
Rectangle clipr; /* clipping region */
int depth; /* number of bits of storage per pixel */
int nchan; /* number of channels */
ulong chan; /* channel descriptions */
Memdata *data; /* pointer to data */
int zero; /* data->bdata+zero==&byte containing (0,0) */
ulong width; /* width in words of a single scan line */
Memlayer *layer; /* nil if not a layer*/
ulong flags;
...
} Memimage;
typedef struct Memdrawparam
{
Memimage *dst;
Rectangle r;
Memimage *src;
Rectangle sr;
Memimage *mask;
Rectangle mr;
...
} Memdrawparam;
int drawdebug;
int memimageinit(void)
ulong* wordaddr(Memimage *i, Point p)
uchar* byteaddr(Memimage *i, Point p)
void memimagemove(void *from, void *to)
Memimage* allocmemimage(Rectangle r, ulong chan)
Memimage* allocmemimaged(Rectangle r, ulong chan, Memdata *data)
Memimage* readmemimage(int fd)
Memimage* creadmemimage(int fd)
int writememimage(int fd, Memimage *i)
void freememimage(Memimage *i)
int memsetchan(Memimage*, ulong)
int loadmemimage(Memimage *i, Rectangle r,
uchar *buf, int nbuf)
int cloadmemimage(Memimage *i, Rectangle r,
uchar *buf, int nbuf)
int unloadmemimage(Memimage *i, Rectangle r,
uchar *buf, int nbuf)
void memfillcolor(Memimage *i, ulong color)
void memarc(Memimage *dst, Point c, int a, int b, int thick,
Memimage *src, Point sp, int alpha, int phi, Drawop op)
void mempoly(Memimage *dst, Point *p, int np, int end0,
int end1, int radius, Memimage *src, Point sp, Drawop op)
void memellipse(Memimage *dst, Point c, int a, int b,
int thick, Memimage *src, Point sp, Drawop op)
void memfillpoly(Memimage *dst, Point *p, int np, int wind,
Memimage *src, Point sp, Drawop op)
void memimageline(Memimage *dst, Point p0, Point p1, int end0,
int end1, int radius, Memimage *src, Point sp, Drawop op)
void memimagedraw(Memimage *dst, Rectangle r, Memimage *src,
Point sp, Memimage *mask, Point mp, Drawop op)
int drawclip(Memimage *dst, Rectangle *dr, Memimage *src,
Point *sp, Memimage *mask, Point *mp,
Rectangle *sr, Rectangle *mr)
int drawclipnorepl(Memimage *dst, Rectangle *dr, Memimage *src,
Point *sp, Memimage *mask, Point *mp,
Rectangle *sr, Rectangle *mr)
Rectangle memlinebbox(Point p0, Point p1, int end0, int end1,
int radius)
int memlineendsize(int end)
Memsubfont* allocmemsubfont(char *name, int n, int height,
int ascent, Fontchar *info, Memimage *i)
Memsubfont* openmemsubfont(char *name)
void freememsubfont(Memsubfont *f)
Point memsubfontwidth(Memsubfont *f, char *s)
Memsubfont* getmemdefont(void)
Point memimagestring(Memimage *dst, Point p, Memimage *color,
Point cp, Memsubfont *f, char *cs)
int iprint(char *fmt, ...)
int hwdraw(Memdrawparam *param)
DESCRIPTION
The Memimage type defines memory-resident rectangular pictures and the
methods to draw upon them; Memimages differ from Images (see draw(2))
in that they are manipulated directly in user memory rather than by
RPCs to the /dev/draw hierarchy. The memdraw library is the basis for
the kernel draw(3) driver and also used by a number of programs that
must manipulate images without a display.
The r, clipr, depth, nchan, and chan structure elements are identical
to the ones of the same name in the Image structure.
The flags element of the Memimage structure holds a number of bits of
information about the image. In particular, it subsumes the purpose of
the repl element of Image structures.
Memimageinit initializes various static data that the library depends
on, as well as the replicated solid color images memopaque, memtrans‐
parent, memblack, and memwhite. It should be called before referring
to any of these images and before calling any of the other library
functions. It returns non-zero on error.
Each Memimage points at a Memdata structure that in turn points at the
actual pixel data for the image. This allows multiple images to be as‐
sociated with the same Memdata. The first word of the data pointed at
by the base element of Memdata points back at the Memdata structure, so
that the memory allocator (see pool(2)) can compact image memory using
memimagemove.
Because images can have different coordinate systems, the zero element
of the Memimage structure contains the offset that must be added to the
bdata element of the corresponding Memdata structure in order to yield
a pointer to the data for the pixel (0,0). Adding width machine words
to this pointer moves it down one scan line. The depth element can be
used to determine how to move the pointer horizontally. Note that this
method works even for images whose rectangles do not include the ori‐
gin, although one should only dereference pointers corresponding to
pixels within the image rectangle. Wordaddr and byteaddr perform these
calculations, returning pointers to the word and byte, respectively,
that contain the beginning of the data for a given pixel.
Allocmemimage allocages images with a given rectangle and channel de‐
scriptor (see strtochan in graphics(2)), creating a fresh Memdata
structure and associated storage. Allocmemimaged is similar but uses
the supplied Memdata structure rather than a new one. The readmemimage
function reads an uncompressed bitmap from the given file descriptor,
while creadmemimage reads a compressed bitmap. Writememimage writes a
compressed representation of i to file descriptor fd. For more on
bitmap formats, see image(6). Freememimage frees images returned by
any of these routines. The Memimage structure contains some tables
that are used to store precomputed values depending on the channel de‐
scriptor. Memsetchan updates the chan element of the structure as well
as these tables, returning -1 if passed a bad channel descriptor.
Loadmemimage and cloadmemimage replace the pixel data for a given rec‐
tangle of an image with the given buffer of uncompressed or compressed
data, respectively. When calling cloadmemimage, the buffer must con‐
tain an integral number of compressed chunks of data that exactly cover
the rectangle. Unloadmemimage retrieves the uncompressed pixel data
for a given rectangle of an image. All three return the number of
bytes consumed on success, and -1 in case of an error.
Memfillcolor fills an image with the given color, a 32-bit number as
described in color(2).
Memarc, mempoly, memellipse, memfillpoly, memimageline, and memimage‐
draw are identical to the arc, poly, ellipse, fillpoly, line, and gen‐
draw, routines described in draw(2), except that they operate on Memim‐
ages rather than Images. Similarly, allocmemsubfont, openmemsubfont,
freememsubfont, memsubfontwidth, getmemdefont, and memimagestring are
the Memimage analogues of allocsubfont, openfont, freesubfont, strsub‐
fontwidth, getdefont, and string (see subfont(2) and graphics(2)), ex‐
cept that they operate only on Memsubfonts rather than Fonts.
Drawclip takes the images involved in a draw operation, together with
the destination rectangle dr and source and mask alignment points sp
and mp, and clips them according to the clipping rectangles of the im‐
ages involved. It also fills in the rectangles sr and mr with rectan‐
gles congruent to the returned destination rectangle but translated so
the upper left corners are the returned sp and mp. Drawclipnorepl does
the same as drawclip but avoids clamping sp and mr within the image
rectangle of source and mask when replicated. Drawclip and drawclip‐
norepl return zero when the clipped rectangle is empty. Memlinebbox
returns a conservative bounding box containing a line between two
points with given end styles and radius. Memlineendsize calculates the
extra length added to a line by attaching an end of a given style.
The hwdraw and iprint functions are no-op stubs that may be overridden
by clients of the library. Hwdraw is called at each call to memimage‐
draw with the current request's parameters. If it can satisfy the re‐
quest, it should do so and return 1. If it cannot satisfy the request,
it should return 0. This allows (for instance) the kernel to take ad‐
vantage of hardware acceleration. Iprint should format and print its
arguments; it is given much debugging output when the global integer
variable drawdebug is non-zero. In the kernel, iprint prints to a ser‐
ial line rather than the screen, for obvious reasons.
SOURCE
/sys/src/libmemdraw
SEE ALSO
addpt(2), color(2), draw(2), graphics(2), memlayer(2), stringsize(2),
subfont(2), color(6), utf(6)
BUGS
Memimagestring is unusual in using a subfont rather than a font, and in
having no parameter to align the source.
MEMDRAW(2)