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im_render(3)                                                      im_render(3)




NAME

       im_render, im_render_fade, im_cache - make image in the background


SYNOPSIS

       #include <vips/vips.h>

       int im_render_fade( IMAGE *in, IMAGE *out, IMAGE *mask,
         int width, int height, int max,
         int fps, int steps,
         int priority,
         void (*notify)( IMAGE *, Rect *, void * ), void *client );

       int im_render( IMAGE *in, IMAGE *out, IMAGE *mask,
         int width, int height, int max,
         void (*notify)( IMAGE *, Rect *, void * ), void *client );

       int im_cache( IMAGE *in, IMAGE *out,
         int width, int height, int max );



DESCRIPTION

       im_render_fade(3)  behaves rather like im_copy(3) between images in and
       out, except that it keeps a cache of computed  pixels.  This  cache  is
       made  of  up  to  max  tiles (a value of -1 for max means any number of
       tiles), and each tile is of size width by  height  pixels.  Each  cache
       tile  is made with a call to im_prepare_thread(3), so cache tile calcu-
       lation will be accelerated on multi-CPU machines. If  image  in  repre-
       sents a large computation, im_render_fade(3) can save a lot of time.

       If the notify parameter points to a function, then tiles are not calcu-
       lated immediately, but are added to a job list and  calculated  as  CPU
       becomes available. When a tile has been calculated, the notify function
       is passed the image which was being cached, the area of the image which
       is  now  available,  and a client pointer.  The notify function will be
       called by a background thread, so you will usually  need  to  implement
       some mechanism to interrupt your main thread and update.

       The  mask  image  is a one band uchar image the same size as out, which
       has 255 for every pixels which is in the cache and 0  everywhere  else.
       You should not read pixels from mask after out has been closed. If mask
       is NULL, then no mask image is written.

       If steps is greater than zero, then pixels in mask are moved between  0
       and  255  as  tiles  age in that many steps. The fps parameter sets how
       many times per second the notify function is called to indicate that an
       updated tile is ready.

       If  priority  is zero, then the render will only run when the system is
       idle, and only a few renders will run at any time. Higher  values  will
       cause the render to happen more quickly.

       im_cache(3) is a convenience function for im_render_fade(3) that caches
       image pixels synchronously. If you ask for an area not  in  the  cache,
       execution blocks until the area has been calculated.

       im_render(3) is deprecated: it is the old interface to the render func-
       tion, before the fps and steps parameters were added.



RETURN VALUE

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


SEE ALSO

       im_prepare(3)


AUTHOR

       J Cupitt, 2003



                                5 October 2003                    im_render(3)

im_render 7.14.5 - Generated Sat Sep 6 06:35:26 CDT 2008
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