Develop Reference

How can I make an image as big as possible, keeping the original aspect ratio and not cutting parts of the image?

Th main question is in the title, but here is the issues I am having getting it working:
I have an image that I am trying to size to a page depending on the size of the window. I want to keep the original aspect ratio of the image which may be wider or taller. I figured out a way to get the aspect ratio, but is there a way to figure out how much space I have to make it both in width and height based on the other items in the screen?
From there I can figure out how to resize accordingly.
I don't want to base it on the size of the window because there might be other items there. I am also using ionic2/angular2, but I don't really think that plays a role in this issue.

The easiest way to achieve this, and the solution I commonly use myself, is using the CSS background-size property. No JS is required, just a few adjustments to your HTML and CSS.
Basically what you have to do is get rid of your <img> element and instead create a <div>. Adjust your layout to give this div the appropriate size and position, and then, via CSS, give it a background-image. You will end up with something like this:
CSS:
#myImg {
background-image: url("../resources/img/myPic.png");
background-size: contain;
background-repeat: no-repeat;
background-position: center;
}
HTML:
<div id="myImg">
</div>
The CSS properties I have set for #myImg do the following:
background-image: Set the path for the image
background-size: contain: Use the contain value, which scales the image to the largest size such that both its width and its height can fit inside the div. This is where all the magic happens behind the scenes
background-repeat: no repeat: Disable repetition of the background image. If this is not set, then the image is tiled so that the entire div is covered, which we don't want.
background-position: center: Position the image in the center of the div.
Browser support

Issue with iFrame Element not re-sizing within container

I am working on a small VA project and I am attempting to pull stats from another website. The only way I have been able to find out how to do this, is by using an iFrame with the clip function.
Website is: NWGlobalVA.com
Now the Issue I am having is if you go to the main page and re-size the browser in anyway it pushes behind the map element. I have tried everything in my knowledge and research to make it re-size with the container.
Below is the code I use with the iFrame and CSS to do the clipping. Any help would be much more appreciated then you will understand. I have been trying to do this for a couple days now. Ideally I would rather just get the information once every 15 minutes and pass it to my database. However on the website none of the tables are defined and I would know how to go about that.
<style>
.iframeb {
position: absolute;
left:-384px;
right:0px;
top: -145px;
clip: rect(190px, 625px, 350px, 400px);
}</style>
<iframe width="890" height="1900" src="http://fscloud-infotool.de/index.php?page=vasystem&subpage=vadetails&id=10277" class="iframeb" scrolling="no" frameborder="0"></iframe>

The way I deal with iframe size is with javascript (jquery):
I calculated the original iframe aspect ratio by taking the width/height. So in your case: 890/1900.
<script>
function size_iFrame()
{
// If the width and height of the iframe are set
// as attributes (<iframe width='890' height='1900'>),
// you can have the js calculate it for you.
// aspect= $('iframe').attr('width') / $('iframe').attr('height');
aspect= 0.47;
$('iframe').css('width', '100%');
$('iframe').css('height', $('iframe').width() / aspect);
}
$(document).ready(function()
{
size_iFrame();
$(window).resize(function()
{
size_iFrame();
});
}
</script>
This will fit the iframe to the width of its container and give it the same aspect ratio as it initially had.
Edit: To answer your question, i'd call it from the ready callback and setup and window resize callback to call every time the screen size changes. I edited my code above to show this.
Edit2: As #mugé points out, you'll also need to remove your iframe css styling for my method to work.

In responsive design, I assign the iframe a container sized inside the CSS. For example,
CSS
.iframe_container {
display: inline;
float: left;
width: 89%; //whatever width you want
}
You will need to eliminate your .iframeb absolute, right, left positionings, because the container will take care of it all, unless you are talking about the 'List' parameters on top of the map, I would try to use #media to arrange clean lists according to screen sizes for the .iframeb class.

How to constrain rendered HTML code inside a div

I have a function that renders the HTML code from a textarea into a div of a certain size. The size of this div is determined when the page loads and is generally about 45% the width of the browser. I would like to know if there is any way to constrain what is rendered to not go out of the bounds of this div, but to instead add scrollbars if the rendered content exceeds the boundaries.
Basically, I'd like this div to behave like a browser window would when you render an HTML web page. Here is the code I have that does the rendering:
$(document).ready(function(){
$("#showmeImg").click(function(){
$("#outputContainer").html($(myEditor.getValue()));
});
});
So when 'showmeImg' is clicked, the contents of 'myEditor' is rendered and place within the 'outputContainer' div tag. All I have for this div tag are basic styling like background color, width, and height.

You should be able to get that effect using CSS. If you are setting the width programatically (as your question seems to suggest), then all you would need to do is set the height and overflow styles to get the desired behavior. Something like this:
#outputContainer {
height: 300px;
overflow: auto;
}
If you want the scrollbars to always be there (regardless of whether or not scrolling is needed for the current content), use overflow: scroll;.

You should add the CSS Rule 'overflow:auto' to the containing div. If the content spills outside of the div, scroll bars will be added automatically.

Have you tried something like this?
#outputContainer {
ovwerflow-y: auto;
}
This will add a vertical scrollbar, when there is enough content inside your container.
There are many nice jQuery plugins for adding nicer scrollbars though :).
http://enscrollplugin.com/ for example.

adjusting height of div based on internal div

I have a set of divs like so:
<div id="textArea">
<div id="text"></div>
</div>
CSS properties:
#textArea {
height: auto !important;
min-height: 2em;
overflow: hidden;
}
#text{
display: none;
}
I'm filling in the div with the id of "text" with error messages coming back from a POST request using jQuery. The size of the data coming back is not static, but my problem is that the div is not adjusting.
I am basically trying to mimic the Ruby on Rails default flash message that will push divs further down the page with a dynamically adjusted div.

I think you are simply doing too much - A div should automatically expand to fit the text content inside it, unless you have a specific rule saying otherwise. Do you have a rule that specifies a height for all divs? Is that why you have the height: auto !important here? Are you using a reset stylesheet? Something external to these rules is affecting your divs.
Hope that this points you the right way.

Div's should update height and width automatically unless otherwise told to. What is your jQuery code to update the div? What are you using to reveal the div to the browser (since it's currently set to display:none)? Have you tried using firebug to inspect the elements?

javascript resize background image

Is it possible to resize a background image on load using javascript? I don't care about dynamically resizing the image according to window size or anything, I just want to take large images and resize them to a specific width and height so that the full image fits inside a specific layout.
WORK AROUND:
I did what the people below said and used a regular tag that I sized accordingly and positioned absolutely in the containing div. I then used the z-index property to push it to the background.
img.background {
position: absolute;
top: 0;
left: 0;
width: 960px;
z-index: 0;
}

It's not possible to [reliably, x-browser] scale a background image in any way at this point, but it is available in CSS3 (spec) so hope exists for the future.
Use an actual if you want to scale, in which case yes of course you can resize whenever you wish.

Background images cannot be resized.
Your best call is to use an <img> with position:absolute