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NAME
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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
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SYNOPSIS
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#include <u.h>
#include <u.h>
#include <libc.h>
#include <draw.h>
#include <memdraw.h>
typedef struct Memdata
{
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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? */
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} Memdata;
enum {
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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 */
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};
typedef struct Memimage
{
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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;
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} Memimage;
typedef struct Memdrawparam
{
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Memimage *dst;
Rectangle r;
Memimage *src;
Rectangle sr;
Memimage *mask;
Rectangle mr;
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} 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,
int cloadmemimage(Memimage *i, Rectangle r,
int unloadmemimage(Memimage *i, Rectangle r,
void memfillcolor(Memimage *i, ulong color)
void memarc(Memimage *dst, Point c, int a, int b, int thick,
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Memimage *src, Point sp, int alpha, int phi, Drawop op)
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void mempoly(Memimage *dst, Point *p, int np, int end0,
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int end1, int radius, Memimage *src, Point sp, Drawop op)
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void memellipse(Memimage *dst, Point c, int a, int b,
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int thick, Memimage *src, Point sp, Drawop op)
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void memfillpoly(Memimage *dst, Point *p, int np, int wind,
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Memimage *src, Point sp, Drawop op)
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void memimageline(Memimage *dst, Point p0, Point p1, int end0,
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int end1, int radius, Memimage *src, Point sp, Drawop op)
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void memimagedraw(Memimage *dst, Rectangle r, Memimage *src,
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Point sp, Memimage *mask, Point mp, Drawop op)
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int drawclip(Memimage *dst, Rectangle *dr, Memimage *src,
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Point *sp, Memimage *mask, Point *mp,
Rectangle *sr, Rectangle *mr)
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Rectangle memlinebbox(Point p0, Point p1, int end0, int end1,
int memlineendsize(int end)
Memsubfont* allocmemsubfont(char *name, int n, int height,
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int ascent, Fontchar *info, Memimage *i)
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Memsubfont* openmemsubfont(char *name)
void freememsubfont(Memsubfont *f)
Point memsubfontwidth(Memsubfont *f, char *s)
Point memimagestring(Memimage *dst, Point p, Memimage *color,
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Point cp, Memsubfont *f, char *cs, Drawop op)
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int iprint(char *fmt, ...)
int hwdraw(Memdrawparam *param)
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DESCRIPTION
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The Memimage type defines memory-resident rectangular pictures
and the methods to draw upon them; Memimages differ from Images
(see draw(3)) 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 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,
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 in the Plan 9 kernel, the memory
allocator (see Plan 9’s
pool(3)) 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 origin, 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 allocates images with a given rectangle and channel
descriptor (see strtochan in graphics(3)), 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(7). 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 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 uncompressed 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(3).
Memarc, mempoly, memellipse, memfillpoly, memimageline, and memimagedraw
are identical to the arc, poly, ellipse, fillpoly, line, and gendraw,
routines described in draw(3), except that they operate on Memimages
rather than Images. Similarly, allocmemsubfont, openmemsubfont,
freememsubfont, memsubfontwidth, and memimagestring are the
Memimage analogues of allocsubfont, openfont, freesubfont, strsubfontwidth,
and string (see subfont(3) and graphics(3)), 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 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 parameters. 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.
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SOURCE
SEE ALSO
BUGS
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Memimagestring is unusual in using a subfont rather than a font,
and in having no parameter to align the source.
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