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, drawclipnorepl,
memlinebbox, memlineendsize, allocmemsubfont, openmemsubfont,
freememsubfont, memsubfontwidth, getmemdefont, memimagestring,
hwdraw – drawing routines for memory–resident images|
#include <u.h> |
typedef struct Memdata
typedef struct Memdrawparam
Memimage* allocmemimage(Rectangle r, ulong chan)
int loadmemimage(Memimage *i, Rectangle r,
void memarc(Memimage *dst, Point c, int a, int b, int thick,
Memsubfont* allocmemsubfont(char *name, int n, int height,
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, memtransparent, 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 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 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(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 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(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 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. Drawclipnorepl does the same as drawclip but avoids clamping sp and mr within the image rectangle of source and mask when replicated. Drawclip and drawclipnorepl 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 function is a no–op stub 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.
addpt(2), color(2), draw(2), graphics(2), memlayer(2), stringsize(2),
subfont(2), color(6), utf(6)|
Memimagestring is unusual in using a subfont rather than a font,
and in having no parameter to align the source.|