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Keep divs positioned relative to image

I am trying to create a "map" with divs over cities. I got the map in .svg format and using it as background with background-size: cover. I need the "city-divs" to stay positioned relative to the image (for example London div should be always over London position on my image). I can half-achieve this making the "city divs" absolute and then positioning it using vh and vw. However, if I resize the window or check on different computer, it messes up.
I guess pure css is not the correct way on doing this. Is there a way of achieving this or am I going completely wrong direction?
Closest I got was using this solution found on stackoverflow http://jsfiddle.net/fmenrd4z/ . This works for divs in the center of image just about right. Divs more to the left / right won't work as good.
Currently, I'm using this code.
HTML
<section id="map">
<div id="london">london</div>
<div id="paris">paris</div>
</section>
CSS
#map {
background-image: url(../img/maps/map.svg);
width: 100vw;
height: 90vh;
background-attachment: fixed;
background-position: center;
background-size: cover;
background-repeat: no-repeat;
}
#london {
position: absolute;
left: 31vw;
top: 35vh;
}
#paris {
position: absolute;
left: 60vw;
top: 73vh;
}
I suppose there must be solution for this problem. I've been searching the web for whole day today but didn't found anything.
I'm up for choosing completely different way of doing this. (Is there some javascript library etc..?)
Thanks in advance!

This will never work because you position the divs dimensions that are always changing depending on the screen it is displayed.
There is one of way of doing it by giving a fixed height and width of section #map in pixels for large screens and adding some media queries for mobile screens.
#map {
width: 600px;
height: 300px;
}
#media (max-width: 1024px){
#map {
width: 300px;
height: 150px;
}
}

Center an Image Vertically in a Fixed Position Div

There are tons of questions on SO regarding vertical alignment, but I haven't discovered a clear answer to my problem.
I created a fiddle to show exactly what I'm trying to do.
HTML:
<div id="fade"></div>
<div id="fullscreen">
<img src="http://jira.seraphdevelopment.com/jmajewski/clean/uploads/pictures/n8jvxzd2476480d0.jpg" />
</div>
CSS:
#fade {
/* Cover the entire viewport. */
position: fixed;
top: 0px;
right: 0px;
bottom: 0px;
left: 0px;
/* Transparent Background */
background-color: #000;
opacity: 0.50;
}
#fullscreen {
/* Cover the entire viewport. */
position: fixed;
top: 0px;
right: 0px;
bottom: 0px;
left: 0px;
}
#fullscreen img {
/* Adding the display: block allowed me to center
the image horizontally with the margin: auto. */
display: block;
margin: auto;
/* Limit the size of the image. */
max-width: 80%;
max-height: 80%;
/* This didn't work for me. */
vertical-align: middle;
/* This didn't do anything, either. */
line-height: 100%;
}
I am trying to make a lightbox of sorts, such that the user will click on an image on the page, causing that same image to load up in fullscreen mode. The first div, fade, will be used to cover the entire page with a semi-transparent black background, essentially giving the effect of the page fading away, while also making things modal.
I wanted to be able to nest the image inside the fade div, but I ran into a problem. Setting the opacity on the outer div (to create the fade effect) caused my nested image to inherit the opacity value. Thus, I added a separate div that was identical to the first one, except without the background, and nested the image inside of that.
For the record, I did manage to figure out a workaround to the opacity issue, but I haven't yet implemented it. Credit to Blowski, a SO user who posted this answer to a question regarding opacity:
I do not want to inherit the child opacity from the parent in CSS
The long story short, I have tried quite a few things now in trying to get this image to be centered vertically, but to no avail.
Keep in mind, this solution needs to work with any image!
I am certainly capable of adding a line of code to the $(window).resize() function to center the image manually, but I would like to avoid doing so, if possible. I'm very curious to learn a way around this, as I seem to run into these types of issues more often that I'd like.
Bonus: Why is vertical alignment so difficult for a browser to perform?

Here is one way centering an image in a fixed/absolute positioned div using CSS.
#fullscreen {
/* Cover the entire viewport. */
position: fixed;
top: 0px;
right: 0px;
bottom: 0px;
left: 0px;
}
#fullscreen img {
position: absolute;
top: 0;
bottom: 0;
left: 0;
right: 0;
margin: auto;
/* Limit the size of the image. */
max-width: 80%;
max-height: 80%;
}
The trick is to use position: absolute for the img and set all the offsets to 0, and then margin: auto will center the image.
The max-width and max-height values will work as expected.
The reason this works is that the image has intrinsic dimensions, so the CSS engine has specific values to do the necessary math to center the images both vertically and horizontally.
See demo at: http://jsfiddle.net/audetwebdesign/KG99S/
Comments
Note that this technique works independently of the overlay.
Also, this works regardless of the aspect ratio of the image.
Reference
This technique follows from the CSS2 specification regarding how the horizontal and vertical margins are determined for absolutely positioned inline, replaced elements.
http://www.w3.org/TR/CSS2/visudet.html#abs-replaced-width
and
http://www.w3.org/TR/CSS2/visudet.html#abs-replaced-height

specific image resize with jquery

I've been trying for sometime to replicate an effect seen on this website:
http://www.gregparmasmith.com/
If you play around with the width and height of the window, the images keep proportionate w/h based on their aspect ratio. The images are always loaded with a consistent height, making this slideshow look very nice.
Also notice how wider images (vs thinner images) are resized when just the width of the browser window (not width and height together) is reduced - The images bounce down from the top margin.
He seems to be programming this differently than most responsive jquery image plugins I've seen. There is a parent div container, but it has a static size and seems to not govern the position/sizing of its child images.
Looking at the source, the images top,left,width,height css properties are dynamically being altered.
Any suggestions for how to do this??

The effect seen on that page can be accomplished with just html and css. No javascript needed. He's using percentages as the values for his margins so that as the browser size gets smaller, so does the calculated pixel size of the left and right margins of the div that contains the images. Then by setting the img width to a max-width of a fixed pixel size, say 400px, it will ensure it will only reach a certain width as it does on very large screens.
Then by setting the "width" to a percentage like maybe 100% the image will automatically resize to the size of the containing div because that div is responding the size of the browser.
something like this:
#inside {
max-width: 300px;
margin: 0 auto;
margin-top: 20%;
margin-bottom: 20%;
}
#inside img {
width: 100%
}
http://jsfiddle.net/wRNJ7/1/

I have found a pretty close solution here in this thread:
Vertically center image on page and maintain aspect ratio on resize
Here's a good working demo:
Demo
html, body {height: 100%}
body {
position: relative;
padding: 0;
margin:0;
font-family: sans-serif;
}
.image {
position: relative;
left: 0px;
height: 100%;
background-position: 50% 50%;
background-size: cover;
background-attachment: scroll;
text-align: center;
}
.wrap {
height: 100%;
overflow: hidden;
position: relative;
}
img {
max-width: 70%;
max-height: 70%;
margin: auto;
position: absolute;
top: 0; left: 0; bottom: 0; right: 0;
}
This effect is achieved without any javascript, which at first I thought was undoable. In this demo, the action of the resizing is a little different. In the original website I was trying to model (http://www.gregparmasmith.com/12), it is "clear" that resizing happens only when necessary, so that for a thin image (ex. 500x100): When the browser window is made as thin, no shrinking would occur. Resizing of the image would occur only if the width of the image would exceed the width of the browser.
In this jsfiddle, I think I can notice this same action is happening, but it's not as obvious.

Css float:right 100% Height, image align bottom

Im using a float: right on my website. I want to make that div 100% of the window height minus a 10px margin. I want the height to resize with the page.
I also want the image in it to sit at the bottom of the 'container' minus 10px padding.
I've tried adjusting everything, and am sure its something in the code conflicting but i just can't work it out.
Thanks for any suggestions in advance.

I suggest you use absolute positioning instead of floating for this, you can make elements expand by setting for example top and bottom at the same time.
Absolute positioning could work for the image as well if you set its bottom to 10px (its offset parent will already be the right container, because any position other than the default static makes the element an offset parent).
Quick example:
/* this makes your body take up the whole screen */
html, body { height: 100%; }
/* the positioning magic */
#right { width: 100px; position: absolute;top: 10px; bottom: 10px; right: 20px; }
jsFiddle Demo
​UPDATE: and an updated jsFiddle to show an example on putting another element in the container and positioning it to the bottom.
#image { position: absolute; bottom: 10px; left: 20px; }

Center object on screen when scrolling

I have a web page with a list on the right and a treeview on the right, and have a drag and drop interface to move objects from one to the other. There is a trash can in the middle used to delete items. Problem is, the page could potentially become 5000px long. How can I keep the trash can centered in the screen when the user scrolls? Thanks in advance for your answers!

To keep an element fixed in a particular position, use position: fixed, for example:
#trashcan {
position: fixed;
top: 50%;
left: 50%;
width: 200px;
height: 200px;
margin-left: -100px; /* half the width */
margin-top: -100px; /* half the height */
}
position: fixed is a lot like position: absolute but with the coordinates/position based on the viewport, not the document. So while position: absolute items will scroll with the page, position: fixed items will stay in place in relation to the viewport.

You could use css to fix the position of the trash can.
.trash-can
{
position: fixed;
left: /*value here*/;
top: /*value here*/;
}

The css shown works nicely for small objects. By small, I mean, smaller than the screen height. Objects that are larger than the screen height, cannot be scrolled when position:fixed is used.