I am trying to write a script that automatically add image width and height to all my img. I've already seen this question:

Automatically adding width and height attributes to <img> tags with a PHP function

But I am using jekyll.

My first thought was execute grep on my posts directory and for each occurence of an img, get the image URI and compute its size. Is this possible?

I have also take a look to fastImage, but it does not work well with Jekyll and local files (Here is a Jekyll filter)

Could you give me some hits on how to accomplish this?

I finally came up with a solution, a python script, here it is (I've also created a github gist).

Here is the main idea behind the code:

• Iterate over all blog posts.
• Find all img tags in each post.
• Extract the content of the src attribute.
• Open the image and extract its size.
• Write image size in the img attribues width and height.

The code:

#!/bin/python
from BeautifulSoup import BeautifulSoup
from os.path import basename, splitext
from PIL import Image
import glob

# Path where the posts are, in markdown format
path = "/ruta/ficheros/*.md"

# Iterate over all posts
for fname in glob.glob(path):
    # Open the post
    f = open(fname)
    # Create a BeautifulSoup object to parse the file
    soup = BeautifulSoup(f)
    f.close()
    # For each img tag:
    for img in soup.findAll('img'):
        if img != None:
            try:
                if img['src'].startswith("/assets") == True:
                    # Open the image
                    pil = Image.open("/ruta/carpeta/imagenes" + img['src'])
                    # Get its size
                    width, height = pil.size
                    # Modify img tag with image size
                    img['width'] = str(width) + "px"
                    img['height'] = str(height) + "px"
            except KeyError:
                pass
    # Save the updated post
    with open(fname, "wb") as file:
        file.write(str(soup))

How to use

Just create the script in you machine and change path variable to point where your posts are.

Hope it helps, I've also wrote a blog post about this issue