如何用eulerr生成高分辨率、边缘无模糊的韦恩图？

边缘模糊大多源于输出格式为低分辨率位图，或是未使用矢量格式保存。以下是几个可行的优化方案：

1. 导出为矢量图形格式（推荐） #

矢量图（如PDF、SVG）基于数学路径绘制，放大后不会出现像素化问题。你可以通过R的图形设备直接导出：

library(eulerr)

VennDiag <- euler(c("Drug and alcohol services" = 312, "Mental health services" = 380, 
                    "Drug and alcohol services&Mental health services" = 116))

# 导出为PDF
pdf("venn_diagram.pdf", width = 8, height = 6)
plot(VennDiag, quantities = list(type = "counts", fontsize=13.5), 
     labels = list(cex=1.2, alpha=0.7, labels=c("Drug and alcohol\n services", "Mental health\n services")), 
     fills= list(fill=c("#004e72", "#27a2db"), alpha=0.7), main = "", edges=list(lex=1.5, linejoin = "round"))
dev.off()

# 或者导出为SVG
svg("venn_diagram.svg", width = 8, height = 6)
plot(VennDiag, quantities = list(type = "counts", fontsize=13.5), 
     labels = list(cex=1.2, alpha=0.7, labels=c("Drug and alcohol\n services", "Mental health\n services")), 
     fills= list(fill=c("#004e72", "#27a2db"), alpha=0.7), main = "", edges=list(lex=1.5, linejoin = "round"))
dev.off()

添加linejoin = "round"到edges参数中，能让图形边缘的衔接更平滑。

2. 提高位图分辨率（若需PNG/JPG格式） #

如果必须使用位图格式，通过设置高dpi参数提升清晰度：

# 导出高分辨率PNG
png("venn_diagram.png", width = 8, height = 6, units = "in", res = 600)
plot(VennDiag, quantities = list(type = "counts", fontsize=13.5), 
     labels = list(cex=1.2, alpha=0.7, labels=c("Drug and alcohol\n services", "Mental health\n services")), 
     fills= list(fill=c("#004e72", "#27a2db"), alpha=0.7), main = "", edges=list(lex=1.5, linejoin = "round"))
dev.off()

这里res = 600代表600dpi，数值越高清晰度越好，对应文件体积也会增大。

3. 调整绘图边缘的平滑参数 #

在plot函数的edges列表中，添加lineend = "round"和linejoin = "round"，可让线条端点与衔接处更平滑，减少锯齿感：

plot(VennDiag, quantities = list(type = "counts", fontsize=13.5), 
     labels = list(cex=1.2, alpha=0.7, labels=c("Drug and alcohol\n services", "Mental health\n services")), 
     fills= list(fill=c("#004e72", "#27a2db"), alpha=0.7), main = "", 
     edges=list(lex=1.5, linejoin = "round", lineend = "round"))

内容的提问来源于stack exchange，提问作者Plima167