Bio_informatics_science_technology_image_beyond_2/2026-04-29_img_read-by-magick.qmd at main · iamhealthy/Bio_informatics_science_technology_image_beyond_2 · GitHub

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---
title: png/svg/pdf read by magick
subtitle: png/svg/pdf images read by magick package, and the resultant format
date: 2026-04-29
toc-depth: 4
toc-expand: true
lang: en
---

R包`magick`用三个读取图片的函数，分别是`image_read()`、`image_read_svg()`、和`image_read_pdf()`。

因此测试下其将图片读取后的图片格式是什么。

## 1. 下载png和svg图片

从<https://bioart.niaid.nih.gov/bioart/668>下载png格式（位图图像）和svg格式（矢量图）。

```{r}
"images/" |>
  fs::dir_tree(regexp = "^images/Rabbit0001\\.(png|svg)")
```

## 2. 将svg图片转为pdf格式

图片用microsoft edge浏览器打开svg图片 &rarr; 打印为microsoft pdf。

```{r}
"images/" |>
  fs::dir_tree(regexp = "^images/rabbit")
```

## 3. 读取图片

### 3.1 读取png格式

```{r}
magick |> library()

png <- "images/Rabbit0001.png" |>
  magick::image_read()

png |> image_info()

png |> plot()
```

读取为png格式。

### 3.2 读取svg格式

```{r}
svg <- "images/Rabbit0001.svg" |>
  magick::image_read_svg()

svg |> image_info()
```

读取为png格式。

### 3.3 读取pdf格式

```{r}
pdf <- "images/rabbit0001.pdf" |>
  magick::image_read_pdf()

pdf |> image_info()
```

读取为png格式。

## 4. 用`image_read()`读取svg和pdf

```{r}
# read svg
svg1 <- "images/Rabbit0001.svg" |>
  magick::image_read()

svg1 |> image_info()

svg1 |> plot()
```

读取为svg格式（`image_read()`无法读取pdf）。

## 5. `image_read`读取的svg是否可以嵌入tidyplots？

```{r}
tidyplots |> library()

# View image information
img_info <- svg1 |> magick::image_info()
img_width <- img_info$width; img_height <- img_info$height
# Change to graphical object
img_grob <- svg1 |> grid::rasterGrob()

# Create a data frame relevant to img_grob
df <- tibble::tibble(x = seq(0, img_width, length.out = 100),
  y = seq(0, img_height, length.out = 100))

# The intended width of image
img_intend_width = 50 # unit: mm
# Tailor relative extra spaces of plot
top_extra = 0 # 0 (0%) - 1 (100%)
right_extra = 0; bottom_extra = 0; left_extra = 0

# The width and height of plot
plot_width = img_intend_width * (1 + left_extra + right_extra) # unit: mm
plot_height = img_intend_width * (img_height/img_width) * (1 + top_extra + bottom_extra)

# Plot
p1 <- df |> tidyplot(x = x, y = y) |>
  add_data_points(alpha = 0) |>
  add(ggplot2::annotation_custom(img_grob, xmin = 0, xmax = img_width,
    ymin = img_height, ymax = 0))

p1

p1 |>
  save_plot("images/Rabbit0001_tidyplot.pdf", view_plot = FALSE) |>
  save_plot("images/Rabbit0001_tidyplot.png", view_plot = FALSE)
```

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