1IM_RENDER(3)               Library Functions Manual               IM_RENDER(3)
2
3
4

NAME

6       im_render, im_render_fade, im_cache - make image in the background
7

SYNOPSIS

9       #include <vips/vips.h>
10
11       int im_render_fade( IMAGE *in, IMAGE *out, IMAGE *mask,
12         int width, int height, int max,
13         int fps, int steps,
14         int priority,
15         void (*notify)( IMAGE *, Rect *, void * ), void *client );
16
17       int im_render( IMAGE *in, IMAGE *out, IMAGE *mask,
18         int width, int height, int max,
19         void (*notify)( IMAGE *, Rect *, void * ), void *client );
20
21       int im_cache( IMAGE *in, IMAGE *out,
22         int width, int height, int max );
23
24

DESCRIPTION

26       im_render_fade(3)  behaves rather like im_copy(3) between images in and
27       out, except that it keeps a cache of computed  pixels.  This  cache  is
28       made  of  up  to  max  tiles (a value of -1 for max means any number of
29       tiles), and each tile is of size width by  height  pixels.  Each  cache
30       tile  is made with a call to im_prepare_thread(3), so cache tile calcu‐
31       lation will be accelerated on multi-CPU machines. If  image  in  repre‐
32       sents a large computation, im_render_fade(3) can save a lot of time.
33
34       If the notify parameter points to a function, then tiles are not calcu‐
35       lated immediately, but are added to a job list and  calculated  as  CPU
36       becomes available. When a tile has been calculated, the notify function
37       is passed the image which was being cached, the area of the image which
38       is now available, and a client pointer.
39
40       The  mask  image  is a one band uchar image the same size as out, which
41       has 255 for every pixels which is in the cache and 0  everywhere  else.
42       You should not read pixels from mask after out has been closed. If mask
43       is NULL, then no mask image is written.
44
45       If steps is greater than zero, then pixels in mask are moved between  0
46       and  255  as  tiles  age in that many steps. The fps parameter sets how
47       many times per second the notify function is called to indicate that an
48       updated tile is ready.
49
50       If  priority  is zero, then the render will only run when the system is
51       idle, and only a few renders will run at any time. Higher  values  will
52       cause the render to happen more quickly.
53
54       im_cache(3) is a convenience function for im_render_fade(3) that caches
55       image pixels synchronously. If you ask for an area not  in  the  cache,
56       execution blocks until the area has been calculated.
57
58       im_render(3) is deprecated: it is the old interface to the render func‐
59       tion, before the fps and steps parameters were added.
60
61

RETURN VALUE

63       The function returns 0 on  success,  and  non-zero  on  error,  setting
64       im_error().
65

SEE ALSO

67       im_prepare(3)
68

AUTHOR

70       J Cupitt, 2003
71
72
73
74                                5 October 2003                    IM_RENDER(3)