By default, we fix image heights to height=315, and let the width be calculated proportionally once the image loads. We therefore ignore the actual image size. This is done to:
  • prevent reflows as the page loads images and can determine their actual sizes, especially is the user opens the page at a given ID in the middle of the page
  • create a more uniform media experience by default, unless a custom image size is actually needed e.g. if the image needs to be larger
When the viewport is narrow enough, mobile CSS takes over and forces images to fill 100% of the page width instead.
which renders as:
which renders as:
Here's a very long test image:
Figure 19. Very long test image. Source. And some tall inline maths: .


  1. Image argument
  2. Image
  3. Macro
  4. OurBigBook Markup
  5. OurBigBook Project