Exporting Plots

Overview

webforest supports exporting plots to static image formats for publications, presentations, and reports.

Two Ways to Export

Method	Best For
`save_plot()`	Batch export, scripts, reproducible workflows
Browser download	Interactive exploration, quick exports

Both methods use the same SVG rendering engine, ensuring consistent output.

Using save_plot()

Export a forest plot to SVG, PNG, or PDF:

# Create a spec
spec <- web_spec(data,
  point = "hr", lower = "lower", upper = "upper",
  label = "study", null_value = 1
)

# Save as SVG (vector)
save_plot(spec, "forest_plot.svg")

# Save as PNG (raster)
save_plot(spec, "forest_plot.png", width = 1200)

# Save as PDF
save_plot(spec, "forest_plot.pdf", width = 800)

From htmlwidget Output

You can also save directly from forest_plot() output:

p <- forest_plot(data, point = "hr", lower = "lower", upper = "upper", label = "study")
save_plot(p, "output.svg")

Output Formats

Format	Extension	Use Case	Dependencies
SVG	`.svg`	Vector graphics, web	None
PNG	`.png`	Raster images, documents	`rsvg` package
PDF	`.pdf`	Print, publications	`rsvg` package

Choosing a Format

SVG: Best for web, editable in Illustrator/Inkscape, infinitely scalable
PNG: Best for documents and slides, set scale = 2 for retina displays
PDF: Best for print, preserves vectors, requires rsvg

SVG (Scalable Vector Graphics)

Ideal for web display and further editing
Infinitely scalable without quality loss
Editable in Illustrator, Inkscape, etc.

PNG (Portable Network Graphics)

Best for documents, slides, reports
Set scale = 2 (default) for retina/HiDPI displays
Requires the rsvg package

PDF (Portable Document Format)

Best for print publications
Vector format, scales perfectly
Requires the rsvg package

Options

save_plot(spec, file,
  width = 800,   # Width in pixels
  height = NULL, # Auto-calculated if NULL
  scale = 2      # PNG scaling factor
)

Width and Height

width sets the SVG/canvas width in pixels
height is auto-calculated based on content if NULL
Specify height to force a specific aspect ratio

Scale Factor (PNG only)

The scale parameter multiplies the resolution for PNG output:

# Standard resolution (800px wide)
save_plot(spec, "plot.png", width = 800, scale = 1)

# High resolution for retina displays (1600px wide)
save_plot(spec, "plot.png", width = 800, scale = 2)

# Very high resolution for print (2400px wide)
save_plot(spec, "plot.png", width = 800, scale = 3)

Dependencies

V8 (Required for save_plot)

The V8 package provides JavaScript execution for SVG generation:

install.packages("V8")

rsvg (Required for PNG/PDF)

The rsvg package converts SVG to raster formats:

install.packages("rsvg")

On macOS, you may also need librsvg:

brew install librsvg

Publication-Quality Figures

DPI Calculation

Most journals require 300 DPI figures. To calculate the right settings:

Width in pixels = Width in inches × 300 DPI × scale

For an 8-inch figure at 300 DPI with scale = 3: - width = 800 (base canvas width) - scale = 3 (multiplier for PNG output) - Result: 800 × 3 = 2400 pixels = 8 inches at 300 DPI

For Journal Submission

# High-resolution PNG at 300 DPI equivalent
# 800px * 3 = 2400px for ~8 inch width at 300 DPI
save_plot(spec, "figure1.png", width = 800, scale = 3)

# Or use PDF for vector output
save_plot(spec, "figure1.pdf", width = 800)

For Presentations

# Wide format for slides
save_plot(spec, "slide_figure.png", width = 1200, scale = 2)

For Web

# SVG for crisp display at any zoom level
save_plot(spec, "web_figure.svg", width = 800)

Browser Export

Interactive plots include a download button (visible on hover):

Hover over the plot to reveal the download button (top-right)
Click to open the format menu
Choose SVG or PNG

The browser export uses the same rendering engine as save_plot(), so output is consistent.

Troubleshooting

“SVG generator JavaScript file not found”

The V8 bundle needs to be built. This usually means the package wasn’t installed correctly:

# Reinstall the package
pak::pak("kaskarn/webforest")

PNG export fails

Ensure rsvg is installed and working:

install.packages("rsvg")

# Test it works
rsvg::rsvg_png(charToRaw('<svg width="100" height="100"><circle cx="50" cy="50" r="40"/></svg>'))

Colors look different

The SVG generator resolves theme colors at export time. Ensure you’re using the same theme for both interactive display and export:

my_theme <- web_theme_jama()

# Interactive
forest_plot(spec, theme = my_theme)

# Export
save_plot(web_spec(..., theme = my_theme), "output.svg")

--- title: "Exporting Plots" --- ```{r} #| include: false library(webforest) ``` ## Overview webforest supports exporting plots to static image formats for publications, presentations, and reports. ::: {.callout-tip} ## Two Ways to Export | Method | Best For | |--------|----------| | **`save_plot()`** | Batch export, scripts, reproducible workflows | | **Browser download** | Interactive exploration, quick exports | Both methods use the same SVG rendering engine, ensuring consistent output. ::: ## Using save_plot() Export a forest plot to SVG, PNG, or PDF: ```r # Create a spec spec <- web_spec(data, point = "hr", lower = "lower", upper = "upper", label = "study", null_value = 1 ) # Save as SVG (vector) save_plot(spec, "forest_plot.svg") # Save as PNG (raster) save_plot(spec, "forest_plot.png", width = 1200) # Save as PDF save_plot(spec, "forest_plot.pdf", width = 800) ``` ### From htmlwidget Output You can also save directly from `forest_plot()` output: ```r p <- forest_plot(data, point = "hr", lower = "lower", upper = "upper", label = "study") save_plot(p, "output.svg") ``` ## Output Formats | Format | Extension | Use Case | Dependencies | |--------|-----------|----------|--------------| | SVG | `.svg` | Vector graphics, web | None | | PNG | `.png` | Raster images, documents | `rsvg` package | | PDF | `.pdf` | Print, publications | `rsvg` package | ::: {.callout-note} ## Choosing a Format - **SVG**: Best for web, editable in Illustrator/Inkscape, infinitely scalable - **PNG**: Best for documents and slides, set `scale = 2` for retina displays - **PDF**: Best for print, preserves vectors, requires `rsvg` ::: ### SVG (Scalable Vector Graphics) - Ideal for web display and further editing - Infinitely scalable without quality loss - Editable in Illustrator, Inkscape, etc. ### PNG (Portable Network Graphics) - Best for documents, slides, reports - Set `scale = 2` (default) for retina/HiDPI displays - Requires the `rsvg` package ### PDF (Portable Document Format) - Best for print publications - Vector format, scales perfectly - Requires the `rsvg` package ## Options ```r save_plot(spec, file, width = 800, # Width in pixels height = NULL, # Auto-calculated if NULL scale = 2 # PNG scaling factor ) ``` ### Width and Height - `width` sets the SVG/canvas width in pixels - `height` is auto-calculated based on content if `NULL` - Specify `height` to force a specific aspect ratio ### Scale Factor (PNG only) The `scale` parameter multiplies the resolution for PNG output: ```r # Standard resolution (800px wide) save_plot(spec, "plot.png", width = 800, scale = 1) # High resolution for retina displays (1600px wide) save_plot(spec, "plot.png", width = 800, scale = 2) # Very high resolution for print (2400px wide) save_plot(spec, "plot.png", width = 800, scale = 3) ``` ## Dependencies ### V8 (Required for save_plot) The `V8` package provides JavaScript execution for SVG generation: ```r install.packages("V8") ``` ### rsvg (Required for PNG/PDF) The `rsvg` package converts SVG to raster formats: ```r install.packages("rsvg") ``` On macOS, you may also need librsvg: ```bash brew install librsvg ``` ## Publication-Quality Figures ::: {.callout-tip} ## DPI Calculation Most journals require 300 DPI figures. To calculate the right settings: **Width in pixels = Width in inches × 300 DPI × scale** For an 8-inch figure at 300 DPI with `scale = 3`: - `width = 800` (base canvas width) - `scale = 3` (multiplier for PNG output) - Result: 800 × 3 = 2400 pixels = 8 inches at 300 DPI ::: ### For Journal Submission ```r # High-resolution PNG at 300 DPI equivalent # 800px * 3 = 2400px for ~8 inch width at 300 DPI save_plot(spec, "figure1.png", width = 800, scale = 3) # Or use PDF for vector output save_plot(spec, "figure1.pdf", width = 800) ``` ### For Presentations ```r # Wide format for slides save_plot(spec, "slide_figure.png", width = 1200, scale = 2) ``` ### For Web ```r # SVG for crisp display at any zoom level save_plot(spec, "web_figure.svg", width = 800) ``` ## Browser Export Interactive plots include a download button (visible on hover): 1. Hover over the plot to reveal the download button (top-right) 2. Click to open the format menu 3. Choose SVG or PNG The browser export uses the same rendering engine as `save_plot()`, so output is consistent. ## Troubleshooting ### "SVG generator JavaScript file not found" The V8 bundle needs to be built. This usually means the package wasn't installed correctly: ```r # Reinstall the package pak::pak("kaskarn/webforest") ``` ### PNG export fails Ensure `rsvg` is installed and working: ```r install.packages("rsvg") # Test it works rsvg::rsvg_png(charToRaw('<svg width="100" height="100"><circle cx="50" cy="50" r="40"/></svg>')) ``` ### Colors look different The SVG generator resolves theme colors at export time. Ensure you're using the same theme for both interactive display and export: ```r my_theme <- web_theme_jama() # Interactive forest_plot(spec, theme = my_theme) # Export save_plot(web_spec(..., theme = my_theme), "output.svg") ```