R语言：VennDiagram包能否实现类似leaflet的自定义填充样式？

核心差异：底层渲染机制不同 #

leaflet基于网页HTML/CSS渲染，所以能通过注入CSS字符串定制样式；但VennDiagram依赖R的grid绘图系统生成静态矢量/位图图形，不支持CSS语法，直接给fill参数传CSS字符串自然无效。

可行实现方案 #

方案1：修改VennDiagram生成的grid图形对象 #

VennDiagram返回的是grid图形对象，我们可以手动替换其中的填充属性为grid支持的交叉阴影图案，需要借助gridPatterns包实现：

library(shiny)
library(VennDiagram)
library(grid)
library(gridPatterns)

ui <- fluidPage(
    plotOutput("venn")
)

server <- function(input, output, session ) {
    
    set.seed(20190708)
    genes <- paste("gene",1:1000,sep="")
    x <- list(
      A = sample(genes,300), 
      B = sample(genes,525), 
      C = sample(genes,440)
    )
    
    display_venn <- function( x ) {
      grid.newpage()
      venn_object <- venn.diagram(
        x,
        filename=NULL,
        fill = c("red","blue","green") # 先占位，后续替换填充样式
      )
      
      # 定义不同颜色的交叉阴影图案
      cross_hatch_A <- pattern("crosshatch", colour = "white", fill = "red", density = 0.3)
      cross_hatch_B <- pattern("crosshatch", colour = "white", fill = "blue", density = 0.3)
      cross_hatch_C <- pattern("crosshatch", colour = "white", fill = "green", density = 0.3)
      
      # 替换对应分组的填充属性
      venn_object[[1]]$gp$fill <- cross_hatch_A
      venn_object[[2]]$gp$fill <- cross_hatch_B
      venn_object[[3]]$gp$fill <- cross_hatch_C
      
      grid.draw(venn_object)
    }
  output$venn <- renderPlot({
    display_venn(x)
  })
}

shinyApp(ui = ui, server = server)

方案2：改用ggVennDiagram + ggpattern（更直观） #

如果可以切换工具包，基于ggplot2的ggVennDiagram配合ggpattern包能更便捷实现图案填充，语法更贴近常用的ggplot风格：

library(shiny)
library(ggVennDiagram)
library(ggpattern)

ui <- fluidPage(
    plotOutput("venn")
)

server <- function(input, output, session ) {
    
    set.seed(20190708)
    genes <- paste("gene",1:1000,sep="")
    x <- list(
      A = sample(genes,300), 
      B = sample(genes,525), 
      C = sample(genes,440)
    )
    
    display_venn <- function( x ) {
      ggVennDiagram(x) +
        # 设置基础填充色
        scale_fill_manual(values = c("A" = "red", "B" = "blue", "C" = "green")) +
        # 添加交叉阴影图案
        geom_polygon_pattern(
          aes(pattern_fill = name),
          pattern = "crosshatch",
          pattern_colour = "white",
          pattern_density = 0.3,
          pattern_spacing = 0.05
        ) +
        scale_pattern_fill_manual(values = c("A" = "red", "B" = "blue", "C" = "green"))
    }
  output$venn <- renderPlot({
    display_venn(x)
  })
}

shinyApp(ui = ui, server = server)

总结 #

VennDiagram本身不支持CSS注入的方式，但可以通过修改其生成的grid图形对象，或者改用ggVennDiagram+ggpattern的组合，来实现交叉阴影填充的需求。

内容的提问来源于stack exchange，提问作者Eddie Rowe