Struct FilterContext

pub struct FilterContext {
    plan: Rc<FilterPlan>,
    source_surface: SharedImageSurface,
    last_result: Option<FilterOutput>,
    previous_results: HashMap<CustomIdent, FilterOutput>,
    primitive_units: CoordUnits,
    effects_region: Rect,
    _affine: Transform,
    paffine: Transform,
}

Context for rendering a single crate::filters::FilterSpec.

Rendering a crate::filters::FilterSpec involves keeping track of possibly-named results for each filter primitive (e.g. those that have an output attribute). This struct maintains that information, plus all the extra data used during filtering.

Fields

plan: Rc<FilterPlan>

Immutable values used during the execution of a filter property.

source_surface: SharedImageSurface

The source graphic surface.

last_result: Option<FilterOutput>

Output of the last filter primitive.

previous_results: HashMap<CustomIdent, FilterOutput>

Surfaces of the previous filter primitives by name.

primitive_units: CoordUnits

Primtive units

effects_region: Rect

The filter effects region.

_affine: Transform

The filter element affine matrix.

If filterUnits == userSpaceOnUse, equal to the drawing context matrix, so, for example, if the target node is in a group with transform="translate(30, 20)", this will be equal to a matrix that translates to 30, 20 (and does not scale). Note that the target node bounding box isn’t included in the computations in this case.

If filterUnits == objectBoundingBox, equal to the target node bounding box matrix multiplied by the drawing context matrix, so, for example, if the target node is in a group with transform="translate(30, 20)" and also has x="1", y="1", width="50", height="50", this will be equal to a matrix that translates to 31, 21 and scales to 50, 50.

This is to be used in conjunction with setting the viewbox size to account for the scaling. For filterUnits == userSpaceOnUse, the viewbox will have the actual resolution size, and for filterUnits == objectBoundingBox, the viewbox will have the size of 1, 1.

paffine: Transform

The filter primitive affine matrix.

See the comments for _affine, they largely apply here.

Implementations

impl FilterContext

pub fn new( filter: &UserSpaceFilter, plan: Rc<FilterPlan>, source_surface: SharedImageSurface, node_bbox: BoundingBox, ) -> Result<Self, FilterError>

Creates a new FilterContext.

pub fn session(&self) -> &Session

pub fn source_graphic(&self) -> &SharedImageSurface

Returns the surface corresponding to the source graphic.

fn background_image(&self) -> SharedImageSurface

Returns the surface corresponding to the background image snapshot.

fn stroke_paint_image(&self) -> SharedImageSurface

Returns a surface filled with the current stroke’s paint, for StrokePaint inputs in primitives.

Filter Effects 1: https://www.w3.org/TR/filter-effects/#attr-valuedef-in-strokepaint

fn fill_paint_image(&self) -> SharedImageSurface

Returns a surface filled with the current fill’s paint, for FillPaint inputs in primitives.

Filter Effects 1: https://www.w3.org/TR/filter-effects/#attr-valuedef-in-fillpaint

pub fn into_output(self) -> Result<SharedImageSurface, Error>

Converts this FilterContext into the surface corresponding to the output of the filter chain.

The returned surface is in the sRGB color space.

pub fn store_result(&mut self, result: FilterResult)

Stores a filter primitive result into the context.

pub fn paffine(&self) -> Transform

Returns the paffine matrix.

pub fn primitive_units(&self) -> CoordUnits

Returns the primitive units.

pub fn effects_region(&self) -> Rect

Returns the filter effects region.

fn get_unspecified_input(&self) -> FilterInput

Get a filter primitive’s default input as if its in=\"...\" were not specified.

Per https://drafts.fxtf.org/filter-effects/#element-attrdef-filter-primitive-in, “References to non-existent results will be treated as if no result was specified”. That is, fall back to the last result in the filter chain, or if this is the first in the chain, just use SourceGraphic.

fn get_input_raw(&self, in_: &Input) -> Result<FilterInput, FilterError>

Retrieves the filter input surface according to the SVG rules.

pub fn get_input( &self, in_: &Input, color_interpolation_filters: ColorInterpolationFilters, ) -> Result<FilterInput, FilterError>

Retrieves the filter input surface according to the SVG rules.

The surface will be converted to the color space specified by color_interpolation_filters.