crates/typst-pdf/src/extg.rs


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use crate::PdfContext;

/// A PDF external graphics state.
#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
pub struct ExtGState {
    // In the range 0-255, needs to be divided before being written into the graphics state!
    pub stroke_opacity: u8,
    // In the range 0-255, needs to be divided before being written into the graphics state!
    pub fill_opacity: u8,
}

impl Default for ExtGState {
    fn default() -> Self {
        Self { stroke_opacity: 255, fill_opacity: 255 }
    }
}

impl ExtGState {
    pub fn uses_opacities(&self) -> bool {
        self.stroke_opacity != 255 || self.fill_opacity != 255
    }
}

/// Embed all used external graphics states into the PDF.
#[tracing::instrument(skip_all)]
pub(crate) fn write_external_graphics_states(ctx: &mut PdfContext) {
    for external_gs in ctx.extg_map.items() {
        let id = ctx.alloc.bump();
        ctx.ext_gs_refs.push(id);
        ctx.pdf
            .ext_graphics(id)
            .non_stroking_alpha(external_gs.fill_opacity as f32 / 255.0)
            .stroking_alpha(external_gs.stroke_opacity as f32 / 255.0);
    }
}