- Normal image in markdown (original size)

Test
Real examples can be found here. 5 best BPMN stencils
- Solution 1 works almost everywhere:
<img src="http://www.5besttools.com/wp-content/uploads/2017/04/qrcode.png" width="150">
Test
- With certain Markdown implementations (including Mou and Marked 2 (only macOS)) you can append =WIDTHxHEIGHT after the URL of the graphic file to resize the image. Do not forget the space before the =. It does not work with external images.
