Full width (vw viewport) image inside fixed parent container - css

Question

Im trying to accomplish this:
http://codepen.io/Mest/pen/oKBIu?editors=110
.child-div {
width: 100vw;
position: relative;
left: calc(-50vw + 50%);}
but instead of a "child-div" i want to target an img-class, like this:
http://codepen.io/dantveita/pen/ZGdKmd
.parent-div img {
width: 100vw;
position: relative;
left: calc(-50vw + 50%);}
When i do this, im getting a horizontal scrollbar, and im not sure why. Could anyone explain this to me. And if possible, provide a solution?
Thanks

Answer 1

Since you are using position: relative, moving the image to the left doesn't actually take it outside of the document flow, so, according to the browser, it still thinks the image is sticking out.
Because there are no containing elements, there's also no need to use viewport-width over a percentage. For some reason, using viewport-width instead of a percentage adds a little extra space on the right, underneath the scrollbar, even when the image is absolutely positioned.
However, this works:
.parent-div img {
position: absolute;
left: 0;
width: 100%;
}
You may also want to remove the width="1400px" from your image tag, as it isn't necessary and may cause inheritance issues later on.

Answer 2

Im going to go with
.parent-div img {
display:block;
width: 100vw;
position: relative;
left: calc(-50vw + 50%);}
on the img-class for now, while hiding overflow-x, until something comes up that makes hiding the scrollbar prevent users from viewing content.
The reason for using this method, and not closing the "previous" container (which would be the obvious choice) is that i want a quick solution for a wordpress blogtemplate, where all images given a specific img-class will stretch full width, when media is inserted from post-editor.
Heres an example of the effect im looking for (theverge.com is obviously closing containers):
http://www.theverge.com/2015/8/4/9090897/mlb-bam-live-streaming-internet-tv-nhl-hbo-now-espn