使用Knitr在pdf文档中设置多个图像之间的空间

Question

我想使用Rmarkdown获取此乳胶文档（因为我需要从源文件夹中自动选择不同的图像）。

现在，我将以下命令用于.tex文件，其中包含乳胶包装和设置

---
output: 
    pdf_document:
        includes:
            in_header: "header.tex"
---

#```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
#```

#```{r, echo=FALSE, out.width="2.3cm", out.height="2.78cm"}
knitr::include_graphics(c("AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png"))
#```

#```{r, echo=FALSE, out.width="2.3cm", out.height="2.78cm"}
knitr::include_graphics(c("AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png"))
#```

#```{r, echo=FALSE, out.width="2.3cm", out.height="2.78cm"}
knitr::include_graphics(c("AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png","AF_0.png"))
#```

结果不佳，因为图像太近且居中。如何获得类似的结果？ 谢谢