result
attribute value within the same filter effect container. If no value
is provided and this is the first filter effect primitive, then the
input will be SourceGraphic. If no value is provided and this
is a subsequent filter effect primitive, then this filter effect
primitive will use the result from the previous filter primitive as
its input. If the value for result appears multiple times within a given
filter container, then a reference to that result will use the closest
preceding filter primitive with the given value for the result
results. Forward references to results are an error and will not draw.
Definitions for the seven possible options:
SourceGraphicThis keyword represents the appearance of
grobs before they are being filtered. For raster effects filter
primitives, the grobs will be rasterized into an initially clear
RGBA raster in image space. Pixels left untouched by the original
graphic will be left clear. The image is specified to be rendered in
linear RGBA pixels. The alpha channel of this image captures any
anti-aliasing specified by SVG. (Since the raster is linear, the
alpha channel of this image will represent the exact percent
coverage of each pixel.)SourceAlphaThis keyword represents the appearance of
grobs before they are being filtered.SourceAlphahas all of
the same rules asSourceGraphicexcept that only the alpha
channel is used. The input image is an RGBA image consisting of
implicitly black color values for the RGB channels, but whose alpha
channel is the same asSourceGraphic. If this option is used,
then some implementations might need to rasterize the graphics
elements in order to extract the alpha channel.BackgroundImageThis keyword represents an image
snapshot of the canvas under the filter region at the time that the
referring grob is being filtered.BackgroundAlphaSame asBackgroundImageexcept
only the alpha channel is used.FillPaintThis keyword represents the value of thefillproperty on the grob being filtered. TheFillPaintimage has conceptually infinite extent. Frequently
this image is opaque everywhere, but it might not be if the "paint"
itself has alpha, as in the case of a gradient or pattern which
itself includes transparent or semi-transparent parts.StrokePaintThis keyword represents the value of thecolproperty on the grob being filtered. TheStrokePaintimage has conceptually infinite
extent. Frequently this image is opaque everywhere, but it might not
be if the "paint" itself has alpha, as in the case of a gradient or
pattern which itself includes transparent or semi-transparent parts.resultargument of a filter
primitive.