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Overview

PngBackend renders a Scene to PNG bytes. This backend requires the png feature flag and uses resvg to rasterize SVG scenes.
This backend requires the png feature:
[dependencies]
kuva = { version = "0.1", features = ["png"] }

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Usage

use kuva::backend::png::PngBackend;
use kuva::render::render::Scene;

let scene = /* your Scene */;
let png_bytes = PngBackend::new()
    .with_scale(2.0)
    .render_scene(&scene)
    .expect("Failed to render PNG");

std::fs::write("plot.png", png_bytes).unwrap();

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Constructor

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new

Creates a new PNG backend with default scale factor (2.0). 
let backend = PngBackend::new();
Returns: PngBackend with scale = 2.0

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default

Alias for new().

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Methods

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with_scale

Sets the pixel density multiplier.
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scale
f32
required
Pixel density multiplier:
  • 1.0 = same logical pixel dimensions as SVG
  • 2.0 = retina/HiDPI quality (default)
  • Higher values produce larger, higher-resolution images
Returns: Self for method chaining Example: 
let backend = PngBackend::new()
    .with_scale(3.0);  // 3x resolution

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render_scene

Renders a Scene to PNG bytes.
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scene
&Scene
required
The scene to render
Returns: Result<Vec<u8>, String>
  • Ok(bytes) - PNG file data ready to write
  • Err(msg) - Error message if rendering failed
Example: 
let png = backend.render_scene(&scene)?;
std::fs::write("plot.png", png)?;

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Implementation

The PNG backend:
  1. Renders the scene to SVG using SvgBackend
  2. Loads system fonts into a resvg font database
  3. Parses the SVG with usvg
  4. Rasterizes to a pixmap at the specified scale
  5. Encodes as PNG

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Convenience Function

For one-shot rendering, use: 
use kuva::render_to_png;

let plots = vec![scatter.into()];
let layout = Layout::auto_from_plots(&plots);
let png = render_to_png(plots, layout, 2.0)?;

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Source

src/backend/png.rs

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