Re: GEGL ops: full-image processing (ignorance of ROI?)

[Øyvind Kolås <pippin@xxxxxxxx>]

On Sat, Feb 20, 2010 at 1:05 AM, Danny Robson <danny@xxxxxxxxxxx> wrote:
> On Fri, 19 Feb 2010 21:24:57 +0300
> Eugene Zagidullin <e.asphyx@xxxxxxxxx> wrote:
>
>> Yes, it's just what I mean. But this decomposition is a very
>> CPU-intensive operation. Is there a way to process whole image only
>> once, store output in a kind of cache and later update requested
>> region with cached data? Performing decomposition again and again
>> until whole image will be covered with ROIs and thus cached is waste
>> of time.
>
> I ran into the same problem with gegl:openraw-load. If get_bounding_box
> and importantly get_cached_region both return the entire image, then
> GEGL will submit one process request for the entire image and cache the
> result.
>
> I'm using this trick in a couple of ops currently, and while it
> doesn't appear to be explicitly documented anywhere, it always works.

This isn't a trick but how it is supposed to be done.

get_bounding_box returns the rectangle that has defined output pixels according
to this operation with its given inputs.

The documentation of get_cached_region used to say:

  /* Adjust result rect, adapts the rectangle used for computing results.
   * (useful for global operations like contrast stretching, as well as
   * file loaders to force caching of the full raster).
   */
  GeglRectangle (*get_cached_region)         (GeglOperation       *operation,
                                              const GeglRectangle *roi);

I have changed it, and hopefully improved it, by making it:

  /* The rectangular area that should be processed in one go, by default if not
   * defined the output roi would be returned. This is useful for file loaders
   * and operations like contrast stretching which is a point operation but we
   * need parameters as the minimum/maximum values in the entire input buffer.
   */
  GeglRectangle (*get_cached_region)         (GeglOperation       *operation,
                                              const GeglRectangle *output_roi);

/Øyvind K.

-- 
«The future is already here. It's just not very evenly distributed»
                                                 -- William Gibson
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