如何在R Markdown中使用Cairo PNGs

使用Cairo保存R图形有很多优点( see here, for example ). 例如,在保存PDF时 cairo_pdf

使用 开罗大学pdf 图形设备很容易与ggplot为基础的图形 ggsave() :

library(ggplot2)

ugly_plot <- ggplot(mtcars, aes(x = wt, y = mpg)) +
  geom_point() +
  labs(title = "Some data about cars") +
  theme_gray(base_family = "Papyrus")
ugly_plot

ggsave(ugly_plot, filename = "ugly_plot.pdf", 
       width = 4, height = 2.5, device = cairo_pdf)

开罗大学pdf 在R减价的设备与刀也很容易添加 dev: cairo_pdf

---
title: "Cairo stuff"
output:
  pdf_document:
    dev: cairo_pdf
---

```{r make-ugly-plot, fig.width=4, fig.height=2.5}
library(ggplot2)

ugly_plot <- ggplot(mtcars, aes(x = wt, y = mpg)) +
  geom_point() +
  labs(title = "Some data about cars") +
  theme_gray(base_family = "Papyrus")
ugly_plot
```

使用基于Cairo的png也有好处,因为 Cairo correctly deals with DPI . 如果将通常保存的DPI较高的PNG放入Word或PowerPoint文件中,则图形的尺寸会被夸大且不准确。如果将具有相同高DPI的基于Cairo的PNG放入Word中,则尺寸正确:

将ggplot输出保存为高分辨率Cairo png非常容易 ,但语法与另存为Cairo PDFs略有不同。我们不指定设备,而是指定类型:

ggsave(ugly_plot, filename = "ugly_plot.png", 
       width = 4, height = 2.5, dpi = 300, type = "cairo")

当编织到HTML或Word时,这种对维度的错误理解会带入R标记。有刀子用就好了 type = "cairo" dpi = 300, type = "cairo" Cairo::CairoPNG() ,但是 ggsave(..., type = "cairo")

加上 dpi=300 但是我不能让knitr使用内置的PNG设备 type = cairo type: cairo

---
title: "Cairo stuff"
output:
  html_document: 
    self_contained: no  # to see resulting figure as a file
    dev: png
    type: cairo  # this doesn't do anything
---

```{r make-ugly-plot, fig.width=5, fig.height=3.5, dpi=300}
library(ggplot2)

ugly_plot <- ggplot(mtcars, aes(x = wt, y = mpg)) +
  geom_point() +
  labs(title = "Some data about cars") +
  theme_gray(base_family = "Papyrus")
ugly_plot
```

总而言之,我正在寻找一种方法来使用您从中获得的相同输出 ggsave(..., filename = "blah.png", dpi = 300, type = "cairo") 穿着针织衫。有办法吗?

---
title: "Something"
output:
  pdf_document:
    dev: cairo_pdf  # yay Cairo output
  html_document:  # What needs to go here?
    dev: png
    type: cairo
---