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If you want an image to take up the “full screen” then there wouldn’t be any room for the text to flow around. In that case you could insert an image wrapped in svg tags on its own html page. The text would end before the image and pickup right after.
If, instead, you want it to just take up the full width, with text above/below, then you could do something along the lines of:
Code:
div.image {margin:2em 0; width:100%}
img {width:100%}
<p>Some text paragraph.</p>
<div class="image"><img alt="" src="yourimage.jpg"/></div>
<p>Some text paragraph.</p>
If you want an image to take up less than the full width of the screen then you would need to incorporate the "float" into your div:
Code:
div.image {margin:2em 0; width:75%; float:left}
img {width:100%}
<p>Some text paragraph.</p>
<div class="image"><img alt="" src="yourimage.jpg"/></div>
<p>Some text paragraph.</p>