How to set size for local image using knitr for markdown?

Question

I have a local image that I would like to include in an .Rmd file which I will then knit and convert to HTML slides with Pandoc. Per this post, this will insert the local image :
![Image Title](path/to/your/image)

Is there a way to modify this code to also set the image size?

For finer control over sizes, you might end up having to use an [HTML img tag](http://www.htmlquick.com/reference/tags/img.html) — Marius, Mar 25 '13 at 22:28
second @Marius's comment:http://daringfireball.net/projects/markdown/syntax says "As of this writing, Markdown has no syntax for specifying the dimensions of an image; if this is important to you, you can simply use regular HTML tags." — Ben Bolker, Mar 25 '13 at 22:30
the problem using HTML tags is that the image is no longer recognized as an external resource by the Rmd conversion process, so it won't be included in a stand-alone version of the rendered HTML. — fabians, Sep 29 '14 at 14:45

score 226 · Answer 1 · edited Jun 20 '20 at 09:12

The question is old, but still receives a lot of attention. As the existing answers are outdated, here a more up-to-date solution:

Resizing local images

As of knitr 1.12, there is the function include_graphics. From ?include_graphics (emphasis mine):

The major advantage of using this function is that it is portable in the sense that it works for all document formats that knitr supports, so you do not need to think if you have to use, for example, LaTeX or Markdown syntax, to embed an external image. Chunk options related to graphics output that work for normal R plots also work for these images, such as out.width and out.height.

Example:

```{r, out.width = "400px"}
knitr::include_graphics("path/to/image.png")
```

Advantages:

Over agastudy's answer: No need for external libraries or for re-rastering the image.
Over Shruti Kapoor's answer: No need to manually write HTML. Besides, the image is included in the self-contained version of the file.

Including generated images

To compose the path to a plot that is generated in a chunk (but not included), the chunk options opts_current$get("fig.path") (path to figure directory) as well as opts_current$get("label") (label of current chunk) may be useful. The following example uses fig.path to include the second of two images which were generated (but not displayed) in the first chunk:

```{r generate_figures, fig.show = "hide"}
library(knitr)
plot(1:10, col = "green")
plot(1:10, col = "red")
```

```{r}
include_graphics(sprintf("%sgenerate_figures-2.png", opts_current$get("fig.path")))
```

The general pattern of figure paths is [fig.path]/[chunklabel]-[i].[ext], where chunklabel is the label of the chunk where the plot has been generated, i is the plot index (within this chunk) and ext is the file extension (by default png in RMarkdown documents).

For pdf output, you will have to specify units for the figure dimensions, e.g. `out.width='100pt'`, otherwise latex will throw an error about illegal unit of measure. — andybega, Apr 15 '16 at 11:23
Also works for MS Word output, but the out.width and out.height do not work — Ben, May 23 '16 at 03:57
@andybega Thank you for your comment; I incorporated it into the answer. — CL., Sep 07 '16 at 16:49
This is strange: it works with ioslides Rmd, but not with Rmd to word or html. For the latter two, I get errors: pandoc: Could not fetch ~/Google Drive/SI/DataScience/UAC_JRI/output/Master_Report/SI_logo.png ~/Google Drive/SI/DataScience/UAC_JRI/output/Master_Report/SI_logo.png: openBinaryFile: does not exist (No such file or directory) — jzadra, Jun 22 '17 at 23:50
@jzadra Please create a new question with reproducible code for your issue. At the moment I cannot reproduce your issue (copied the second code snippet verbatim to an RMD file and knitted to HTML and Word). — CL., Jun 23 '17 at 07:01
https://stackoverflow.com/questions/44728551/r-markdown-knit-fails-when-path-includes-for-html-pdf-document-but-works-for — jzadra, Jun 23 '17 at 19:19

score 151 · Answer 2 · edited Feb 17 '20 at 18:55

151

Un updated answer: in knitr 1.17 you can simply use

![Image Title](path/to/your/image){width=250px}

edit as per comment from @jsb

Note this works only without spaces, e.g. {width=250px} not {width = 250px}

edited Feb 17 '20 at 18:55

tjebo

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answered Aug 29 '17 at 19:19

InspectorSands

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I tried this in knitr 1.16 and it didn't work when using ioslides. Has this feature then been removed or is it an ioslides issue? – Dr. Mike Sep 03 '17 at 13:26
2

Does not work for me either, on the latest version of all packages. – slhck Sep 29 '17 at 12:16
6

Works for me using knitr 1.17. Make sure you write without spaces, e.g. `{width=250px}` not `{width = 250px}`. – Samuel Feb 19 '18 at 17:42
2

Works for me, easiest solution by far. – warship Mar 28 '18 at 20:50
2

This wouldn't work for me using `xaringan` with `knitr_1.21`. – Dan Jan 31 '19 at 13:09
On ioslides this is not working yet, using knitr_1.21 – André Costa Feb 11 '19 at 18:37
5

For height AND width `{height=640px width=480px}` - a space between the two, not a comma or anything else. – dsz May 08 '20 at 01:43
1

with in percentage, e.g. `{width=100%}` works as well! – giocomai May 25 '20 at 22:15

score 111 · Accepted Answer · edited Dec 17 '15 at 14:54

111

You can also read the image using png package for example and plot it like a regular plot using grid.raster from the grid package.

```{r fig.width=1, fig.height=10,echo=FALSE}
library(png)
library(grid)
img <- readPNG("path/to/your/image")
 grid.raster(img)
```

With this method you have full control of the size of you image.

edited Dec 17 '15 at 14:54

yoyoyoyosef

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answered Mar 25 '13 at 22:51

agstudy

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Thank you, this works using slidy. (Does not work as well with dzslides, but I don't believe it's an issue with the provided solution). – Adam Smith Mar 28 '13 at 19:07
1

Quotes around filepath are required in `img <- readPNG("path/to/your/image")` but I wasn't able to edit the solution. – Adam Smith Mar 28 '13 at 19:18
1

@AdamSmith I just copied your `path/to/your/image` from your question. Yes the path name is a string,, and you need quotes to define a string. Hope I am clear. – agstudy Mar 28 '13 at 19:48
1

By running this under RStudio, you will create a huge margin to the rendered png. – Paulo E. Cardoso Sep 29 '14 at 16:13
22

Future readers: This answer is [outdated](http://stackoverflow.com/a/36057971/2706569). – CL. Mar 17 '16 at 10:36

score 38 · Answer 4 · edited Mar 21 '18 at 19:23

38

Here's some options that keep the file self-contained without retastering the image:

Wrap the image in `div` tags

<div style="width:300px; height:200px">
![Image](path/to/image)
</div>

Use a stylesheet

test.Rmd

---
title: test
output: html_document
css: test.css
---

## Page with an image {#myImagePage}

![Image](path/to/image)

test.css

#myImagePage img {
  width: 400px;
  height: 200px;
}

If you have more than one image you might need to use the nth-child pseudo-selector for this second option.

edited Mar 21 '18 at 19:23

Ken Williams

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answered Jun 27 '15 at 07:35

Nick Kennedy

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this is a good solution but it can be used with html output only! The other output will ignore the setting – xhudik Feb 22 '16 at 22:05
The `
...
` solution seems very simple. What is the `style` setting to re-scale an image to a fixed percent, maintaining the aspect ratio? – user101089 Sep 19 '17 at 00:52
Try using % instead of px. – Nick Kennedy Sep 19 '17 at 06:21
Can the `
...
` method be used inline with text? I want the image to side directly beside some regular text. Thx! – Cassandra Oct 25 '22 at 19:52
this can only be used with html content. I would recommend using knitr itself over this strategy – thus__ Mar 03 '23 at 19:52

score 21 · Answer 5 · answered Mar 28 '13 at 17:54

21

If you are converting to HTML, you can set the size of the image using HTML syntax using:

  <img src="path/to/image" height="400px" width="300px" />

or whatever height and width you would want to give.

answered Mar 28 '13 at 17:54

Shruti Kapoor

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the problem with this solution is that the image is no longer recognized as an external resource by the Rmd conversion process, so it won't be included in a stand-alone version of the rendered HTML. – fabians Sep 29 '14 at 14:45

Taylor Pellerin · Answer 6 · 2017-12-08T08:35:13.643

11

Had the same issue today and found another option with knitr 1.16 when knitting to PDF (which requires that you have pandoc installed):

![Image Title](path/to/your/image){width=70%}

This method may require that you do a bit of trial and error to find the size that works for you. It is especially convenient because it makes putting two images side by side a prettier process. For example:

![Image 1](path/to/image1){width=70%}![Image 2](path/to/image2){width=30%}

You can get creative and stack a couple of these side by side and size them as you see fit. See https://rpubs.com/RatherBit/90926 for more ideas and examples.

edited Dec 08 '17 at 08:35

answered Dec 08 '17 at 08:29

Taylor Pellerin

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is this not exactly the same as my answer above? – InspectorSands Mar 29 '18 at 12:45
3

@hermestrismegistus nearly, but I am using percent of width rather than pixel width. I found this option to be useful because in my particular case I was putting multiple images side by side, which behaved better this way that when I gave exact width – Taylor Pellerin Mar 30 '18 at 17:15

score 8 · Answer 7 · answered Apr 20 '18 at 21:28

Another option that worked for me is playing with the dpi option of knitr::include_graphics() like this:

```{r}
knitr::include_graphics("path/to/image.png", dpi = 100)
```

... which sure (unless you do the math) is trial and error compared to defining dimensions in the chunk, but maybe it will help somebody.

score 4 · Answer 8 · edited May 23 '17 at 11:47

4

The knitr::include_graphics solution worked well for resizing the figures, but I was unable to figure out how to use it to produce side-by-side resized figures. I found this post useful for doing so.

edited May 23 '17 at 11:47

Community

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answered Oct 16 '16 at 03:46

S.M.

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How to set size for local image using knitr for markdown?

8 Answers8

Resizing local images

Example:

Including generated images

Wrap the image in `div` tags

Use a stylesheet

test.Rmd

test.css

Linked

How to set size for local image using knitr for markdown?

8 Answers8

Resizing local images

Example:

Including generated images

Wrap the image in div tags

Use a stylesheet

test.Rmd

test.css

Linked

Wrap the image in `div` tags