2007-08-29 18:23:50 +02:00
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.TH IM_RENDER 3 "5 October 2003"
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.SH NAME
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im_render, im_render_fade, im_cache \- make image in the background
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.SH SYNOPSIS
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#include <vips/vips.h>
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int im_render_fade( IMAGE *in, IMAGE *out, IMAGE *mask,
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.br
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int width, int height, int max,
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.br
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int fps, int steps,
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.br
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int priority,
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.br
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void (*notify)( IMAGE *, Rect *, void * ), void *client );
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int im_render( IMAGE *in, IMAGE *out, IMAGE *mask,
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.br
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int width, int height, int max,
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.br
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void (*notify)( IMAGE *, Rect *, void * ), void *client );
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int im_cache( IMAGE *in, IMAGE *out,
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.br
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int width, int height, int max );
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.SH DESCRIPTION
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.B im_render_fade(3)
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behaves rather like
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.B im_copy(3)
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between images
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.B in
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and
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.B out,
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except that it keeps a cache of computed pixels. This cache is made of up to
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.B max
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tiles (a value of -1 for
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.B max
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means any number of tiles), and each tile is of size
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.B width
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by
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.B height
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pixels. Each cache tile is made with a call to
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.B im_prepare_thread(3),
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so cache tile calculation will be accelerated on multi-CPU machines. If image
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.B in
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represents a large computation,
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.B im_render_fade(3)
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can save a lot of time.
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If the
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.B notify
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parameter points to a function, then tiles are not calculated immediately, but
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are added to a job list and calculated as CPU becomes available. When a tile has
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been calculated, the notify function is passed the image which was being
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2008-04-15 11:41:02 +02:00
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cached, the area of the image which is now available, and a client pointer.
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The notify function will be called by a background thread, so you will usually
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need to implement some mechanism to interrupt your main thread and update.
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2007-08-29 18:23:50 +02:00
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The
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.B mask
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image is a one band uchar image the same size as out, which has 255 for every
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pixels which is in the cache and 0 everywhere else. You should not read
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pixels from
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.B mask
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after
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.B out
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has been closed. If mask is NULL, then no mask image is written.
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If
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.B steps
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is greater than zero, then pixels in mask are moved between 0 and 255 as tiles
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age in that many steps. The
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.B fps
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parameter sets how many times per second the notify function is called to
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indicate that an updated tile is ready.
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If
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.B priority
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is zero, then the render will only run when the system is idle, and only a few
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renders will run at any time. Higher values will cause the render to happen
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more quickly.
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.B im_cache(3)
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is a convenience function for
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.B im_render_fade(3)
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that caches image pixels synchronously. If you ask for an area not in the cache,
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execution blocks until the area has been calculated.
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.B im_render(3)
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is deprecated: it is the old interface to the render function, before the
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.B fps
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and
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.B steps
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parameters were added.
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.SH RETURN VALUE
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The function returns 0 on success, and non-zero on error, setting
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im_error().
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.SH SEE ALSO
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im_prepare(3)
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.SH AUTHOR
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J Cupitt, 2003
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