Programmatically Create Image from Web-Page or a Single Div

Programmatically create image from web-page or a single DIV

You cannot create image from div for sure but yes you can create dynamic images in php using its gd library.
Following links will help:

http://php.net/manual/en/function.imagecreate.php

http://phptutorial.info/learn/create_images/

Using HTML5/Canvas/JavaScript to take in-browser screenshots

JavaScript can read the DOM and render a fairly accurate representation of that using canvas. I have been working on a script which converts HTML into a canvas image. Decided today to make an implementation of it into sending feedbacks like you described.

The script allows you to create feedback forms which include a screenshot, created on the client's browser, along with the form. The screenshot is based on the DOM and as such may not be 100% accurate to the real representation as it does not make an actual screenshot, but builds the screenshot based on the information available on the page.

It does not require any rendering from the server, as the whole image is created on the client's browser. The HTML2Canvas script itself is still in a very experimental state, as it does not parse nearly as much of the CSS3 attributes I would want it to, nor does it have any support to load CORS images even if a proxy was available.

Still quite limited browser compatibility (not because more couldn't be supported, just haven't had time to make it more cross browser supported).

For more information, have a look at the examples here:

http://hertzen.com/experiments/jsfeedback/

edit
The html2canvas script is now available separately here and some examples here.

edit 2
Another confirmation that Google uses a very similar method (in fact, based on the documentation, the only major difference is their async method of traversing/drawing) can be found in this presentation by Elliott Sprehn from the Google Feedback team:
http://www.elliottsprehn.com/preso/fluentconf/

Render HTML to an image

There is a lot of options and they all have their pro and cons.

Option 1: Use an API

ApiFlash (based on chrome)
EvoPDF (has an option for html)
Grabzit
HTML/CSS to Image API
...

Pros

Execute Javascript
Near perfect rendering
Fast when caching options are correctly used
Scale is handled by the APIs
Precise timing, viewport, ...
Most of the time they offer a free plan

Cons

Not free if you plan to use them a lot

Option 2: Use one of the many available libraries

dom-to-image
wkhtmltoimage (included in the wkhtmltopdf tool)
IMGKit (for ruby and based on wkhtmltoimage)
imgkit (for python and based on wkhtmltoimage)
python-webkit2png
...

Pros

Conversion is quite fast most of the time

Cons

Bad rendering
Does not execute javascript
No support for recent web features (FlexBox, Advanced Selectors, Webfonts, Box Sizing, Media Queries, ...)
Sometimes not so easy to install
Complicated to scale

Option 3: Use PhantomJs and maybe a wrapper library

PhantomJs
node-webshot (javascript wrapper library for PhantomJs)
...

Pros

Execute Javascript
Quite fast

Cons

Bad rendering
No support for recent web features (FlexBox, Advanced Selectors, Webfonts, Box Sizing, Media Queries, ...)
Complicated to scale
Not so easy to make it work if there is images to be loaded ...

Option 4: Use Chrome Headless and maybe a wrapper library

Chrome Headless
chrome-devtools-protocol
Puppeteer (javascript wrapper library for Chrome headless)
...

Pros

Execute Javascript
Near perfect rendering

Cons

Not so easy to have exactly the wanted result regarding:
- page load timing
- viewport dimensions
Complicated to scale
Quite slow and even slower if the html contains external links

Disclosure: I'm the founder of ApiFlash. I did my best to provide an honest and useful answer.