- whenever I inserted stretch-contrast into a graph, GEGL would crash with the error message
** ERROR **: file gegl-operation.c: line 648 (gegl_operation_get_target): assertion failed: (format != NULL)
Adding
#define GEGL_CHANT_PREPARE
and
static void prepare (GeglOperation *operation,
gpointer context_id)
{
gegl_operation_set_format (operation, "input", babl_format ("RGBA float"));
gegl_operation_set_format (operation, "output", babl_format ("RGBA float"));
}
to stretch-contrast.c fixed it.
- I'm trying to implement a Fourier transform filter in GEGL. It uses RGB images with the real part of the complex numbers stored in red, and the imaginary part in green. This should allow for some interesting things, like implementing a frequency filter like this:
<gegl>
<node operation='mono-mixer' red='1.0'/>
<node operation='fourier-transform' inverse='true'/>
<node operation='multiply'>
<node operation='load' path='lowpass.png'/>
</node>
<node operation='fourier-transform'/>
<node operation='colorize' green='0'/>
<layer src=""></gegl>
I have put what I have got so far at http://folk.ntnu.no/hitland/gegl/ , in case anyone is interested.
The current implementation has some issues, the worst of which is that it doesn't use the fast Fourier transform, and therefore is impractically slow for anything much larger than around 128x128, and that my algorithm seems to be wrong anyway, as the images it gives are shifted compared to the examples I find on the net. :-/
Both should be resolved by finding a suitable FFT library or code example to use.
- Some questions:
I guess storing complex data is a slight abuse of the RGB model... Are there any caveats in having negative or excessively large values in pixels?
Could one have pads other than 'input', 'aux' and 'output', for things like composing/decomposing to channels?
Can you have several versions of a node, taking different formats?
- I guess this is already known, but the GEGL tool currently exports XML with a '/' erroneously prepended to relative layer paths.
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