MEMDRAW(2) MEMDRAW(2)
NAME
Memimage, Memdata, Memdrawparam, memimageinit, wordaddr,
byteaddr, memimagemove, allocmemimage, allocmemimaged,
readmemimage, creadmemimage, writememimage, freememimage,
memsetchan, loadmemimage, cloadmemimage, unloadmemimage,
memfillcolor, memarc, mempoly, memellipse, memfillpoly,
memimageline, memimagedraw, drawclip, memlinebbox,
memlineendsize, allocmemsubfont, openmemsubfont,
freememsubfont, memsubfontwidth, getmemdefont,
memimagestring, iprint, hwdraw - drawing routines for
memory-resident images
SYNOPSIS
#include <u.h>
#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;
Page 1 Plan 9 (printed 12/28/24)
MEMDRAW(2) MEMDRAW(2)
...
} Memimage;
typedef struct Memdrawparam
{
Memimage *dst;
Rectangle r;
Memimage *src;
Rectangle sr;
Memimage *mask;
Rectangle mr;
...
} Memdrawparam;
int drawdebug;
void 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)
void mempoly(Memimage *dst, Point *p, int np, int end0,
int end1, int radius, Memimage *src, Point sp)
void memellipse(Memimage *dst, Point c, int a, int b,
int thick, Memimage *src, Point sp)
void memfillpoly(Memimage *dst, Point *p, int np, int wind,
Memimage *src, Point sp)
void memimageline(Memimage *dst, Point p0, Point p1, int end0,
int end1, int radius, Memimage *src, Point sp)
void memimagedraw(Memimage *dst, Rectangle r, Memimage *src,
Point sp, Memimage *mask, Point mp)
int drawclip(Memimage *dst, Rectangle *dr, Memimage *src,
Point *sp, Memimage *mask, Point *mp,
Page 2 Plan 9 (printed 12/28/24)
MEMDRAW(2) MEMDRAW(2)
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 pic-
tures 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 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 struc-
ture.
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 struc-
tures.
Memimageinit initializes various static data that the
library depends on, as well as the replicated solid color
images memopaque, memtransparent, memblack, and memwhite.
It should be called before referring to any of these images
and before calling any of the other library functions.
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 associated 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
Page 3 Plan 9 (printed 12/28/24)
MEMDRAW(2) MEMDRAW(2)
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 origin, although one should only derefer-
ence pointers corresponding to pixels within the image rect-
angle. 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 descriptor (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 chan-
nel descriptor. 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 rectangle of an image with the given buffer of uncom-
pressed or compressed data, respectively. When calling
cloadmemimage, the buffer must contain 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
memimagedraw are identical to the arc, poly, ellipse,
fillpoly, line, and gendraw, routines described in draw(2),
except that they operate on Memimages rather than Images.
Similarly, allocmemsubfont, openmemsubfont, freememsubfont,
memsubfontwidth, getmemdefont, and memimagestring are the
Memimage analogues of allocsubfont, openfont, freesubfont,
strsubfontwidth, getdefont, and string (see subfont(2) and
graphics(2)), except 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
Page 4 Plan 9 (printed 12/28/24)
MEMDRAW(2) MEMDRAW(2)
mask alignment points sp and mp, and clips them according to
the clipping rectangles of the images involved. It also
fills in the rectangles sr and mr with rectangles congruent
to the returned destination rectangle but translated so the
upper left corners are the returned sp and mp. Drawclip
returns 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 memimagedraw with the current request's parame-
ters. If it can satisfy the request, 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
advantage 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 serial 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.
Page 5 Plan 9 (printed 12/28/24)