How to simulate magnifying glass on Web-page image (Javascript)? - javascript

Google has the coolest effects - once it was a Pac-man game, today is apparently the 160th anniversary of the first World Fair, and Google's logo has an image of it. They also turn the mouse into a magnifying glass that can sweep over the picture (the gold ring).
I'm wondering how they do that. It's obviously Javascript, and I looked at the page source, but it's not especially readable (no surprise).

Looking at their source code, it seems they are using rather basic techniques to achieve this.
Ignoring all the embedded nifty animated gif's, there are basically two images - large, and small of the entire scene. The larger image is repeated thrice in the document. Look at the annotated image below to get a better idea of how the zoom works.
The portion inside the magnifying circle is split up in three div's - top, mid, and bottom. The overflow for each div should be hidden. Each div is relatively positioned inside the zoom circle. On mouse move, change the absolute position of the zoom circle to the mouse coordinates. Their example also uses CSS3 for the scaling and adding some animation delays.
Here's a sorta minimal reconstructed example.
Another example where we don't hide the div overflow to reveal the entire thing as a square.

Well, firstly, for anyone who wants to use such an effect, there are loads of jQuery plugins. Here are just a few:
Power Zoomer
Featured Image
Zoomer
Cloud Zoom
Secondly, it's quite easy to achieve. Just load the full-size image, but give it a width smaller than it's actual width, so it is scaled by CSS. Then, use JavaScript+CSS to create a Div (the magnifying glass) with the same image as background, but change the background-position property to the corresponding scaled x,y coordinate that the user's mouse is currently on.
There are other ways of doing it I suppose, and Google might be doing it differently, but this is the most obvious way for me that comes to mind.

Visit http://codeblab.com/glass/ for an real life example and in depth explanation of this technique. Flash and CSS v3 have ample functionality to construct a round magnifying glass.
However, simulate-a-circle-with-overlapping-rectangles works on (many) more platforms.
(DISCLOSURE: codeblab.com is my personal hobby blog with some weak links to my work in The Netherlands.)

There is a full example of magnifying any sort of HTML, including HTML5 at http://www.aplweb.co.uk/blog/js/magnifying-glass/. Works cross-browser too - although rounded corners are a bit iffy on most browsers - so you are going to have to use a box rather than circle.
Here is how to works:
Duplicate the content you want to zoom
Place the duplicated content into another element and set the visible width/height and overflow hidden
Use JavaScript to move the duplicated content so that it moves by the zoom amount * mouse movement. Also move the visible div by the mouse movement.
That is pretty much it too it. There are lots of little things to look out for though to make it work on all browsers.

I don't know how Google does it, since the logo is no longer showing in my area; but this effect can be achieved by clipping the enlarged animated GIF over the regular image using canvas. Alternatively, it is also possible to create create a circular clipping using CSS border-radius (commonly used to implement rounded corners).
EDIT: I've hacked this up together to show the basic technique that you need if you used CSS border-radius: http://jsfiddle.net/yjBuS/

Looks like they're using two images, one for the logo and one for the zoom (the zoomed one is actually sliced, to run the animations separately...?) They probably detect if the mouse is over the normal logo, then show the yellow circle and attach it to the mouse position. Then showing the other image, shifting it opposite of the mouse. Or something similar.

Related

show overlay objects only around the mouse not matter where in the screen

I'm working with svg files and some processing.js code to create a homepage.
It has some animation and static elements but the idea is to have everything the same but with different colours - Like an alternative homepage. I want this alternative to "peek" through as the mouse moves around. Only a small area around the mouse.
Does anyone have any idea how to do that?
since it isn't an image file it's a bit tricky.
I tried doing it by using the an image and the "drawing" element of processing.js thinking it could paint the alternative homepage, however it repeats the image everywhere the mouse go and what i want is for everything to remain in the same position only show the different colours in that spot.
You might consider superimposing two versions of your site, the "top" one completely covering the "bottom" one (make sure all backgrounds are opaque). Then you could try applying an SVG mask to the top page, making it transparent at a specific area and causing the bottom page to shine through. You could modify the mask as the mouse moves.
The other way round - i.e. clipping the top layer - is also thinkable.
I see the risk that this approach is slow and not consistent across browsers - you'd have to give it a try. Speed may differ depending on whether you clip/mask the top or the bottom layer.
W3C SVG Clipping, Masking and Compositing specs
MDN page on clipping and masking
MDN page on applying SVG effects to HTML content
If one version of the page can be converted to other by swapping out colors, SVG filters might be an option as well.

Infinitely tiling the contents of a draggable DIV without duplicating

I am working on a map that is divided into 800x800 150 pixel tiles. These tiles are contained within a jQuery draggable wrapper, which moves the contents of the tiles around inside the parent to achieve a Google Maps style dragging effect. The top left corner is 0,0 and the bottom right is 799x799. I am looking to replicate Google's tiling effect where the user can drag to the left or top of the start point or the right or bottom of the end point and see the tiled (repeated) contents of the DIV in a seamless manner. Using Clone is not an option as it creates duplicates of an already very large (albeit not yet optimised) source which seriously hampered the load times of the page when dragging was performed.
I could best summarise this by saying I need the map itself to have the visual effect and user experience of looping endlessly, but actually only using one instance of the map source. The resulting effect would not be too dissimilar to the repeating background of an image on a page, except with the contents of the map DIV and not an image. When the user drags the map left of anything on the 0 X Axis, it should display X 799, X 798, etc.
I have not had any luck searching for a solution. Is such an effect possible? If so, what would I need to use to achieve it? I am content with simple answers to point me in the right direction; I do not expect somebody to produce a working example that I can cut and paste. Not afraid to research and experiment myself, my problem is I really don't know where to start. I have plenty of experience with Javascript and jQuery but I've never had to do anything quite like this.

Javascript - Display an image under the cursor

I have an HTML chessboard with chess pieces, and everything works. In order to avoid the drag & drop tediousness, I made the chess pieces background-images. On mousedown, I remove the piece at the position, and on mouseup I place it back. The only thing that is missing from the aesthetic is the image of the piece to be displayed under the cursor in-between.
I tried this:
cursor:url('http://upload.wikimedia.org/wikipedia/commons/c/c7/Chess_pdt45.svg'), auto;
But there are several setbacks with this method.
The image cursor needs to be at most 32x32 pixels in order to guaranty compatibility
It's unclear whether the format I want will be supported at all.
I don't know if the cursor image has width and height properties, meaning I cannot resize the image so that it looks exactly like what's on the board.
The cursor position is top-right, whereas it should be centered-centered, since chess pieces are... well, held from their center.
The big question is whether there's a workaround to all of that. Is it, for instance, possible to make a canvas that appears under the mouse?
Unfortunately, you cannot modify cursor properties, like width/height or position...
But, I have found interesting article how to imitate cursor with div element.
http://www.ajaxblender.com/howto-create-custom-image-cursors.html
Hope this helps you!

How did they do those effects in http://artofflightmovie.com/?

I have been trying to understand how they did those effects in http://artofflightmovie.com/ with no success so far. I am not even sure what to google for for help. Could any one ellaborate on it and perhaps put links to plugins\tutorials\other websites doing the same thing?
There is already a similar question, but it didn't help me a bit ^^
Custom scroll bar behavior in Javascript?
All of the answers here so far are spot on and cover various pieces of the execution. Joseph's post about how we 'contained' and 'maneuvered' the site are dead-on, and those mentioning jQuery accurately depict our heavy reliance on it :)
With that said, the other concept of moving along a non-linear path was probably the most difficult part. We literally used an Illustrator file that was setup like a piece of graph paper and drew a bezier path that reflected the movement we wanted from the scrollbar. Then we 'downsampled' the path by converting the curved lines into a bunch of straight lines that represented the curve (similar to downsampling audio waveforms) to keep performance/speed high. We took those coordinates, gave them to our designer, and he created a gigantic design file and literally designed each content section at the designated 'stop' points. Next we mapped each coordinate along the path to a percentage value of the scroll position. We stored these values in a JavaScript array. Lastly we wrote some JS functions that we pipe the scroll position through to determine how to offset the positioning of the site 'container'. (It basically 'tweens' between each coordinate allowing us very fine/precise values at any given scroll percentage) The scroll functionality is handled by a tall div that basically sets our document height to force a scrollbar, and we just read it's position during a Scroll Event and slide the container around to where it should be using the above mentioned functions.
The parallax effect is achieved by applying a percentage of the position offset (what we use to move the container around) and applying it to the sub-containers of the various content sections. This makes the subcontainers move slower or faster than the background, but on the same motion path.
Lastly, the little snowboarders and helicopters (which have CSS3 rotations in addition to x,y movement in some browsers!) are positioned by using a simliar array of 'start' and 'end' positions and tweening between them based on the scroll percentage.
I'll leave it at that to keep this from turning into a book, but I'd be happy to elaborate on specifics if you're interested.
Full disclosure: I was lead developer on the site. I'm not posting to 'toot my own horn' or anything like that, just to be helpful and provide assistance to a fellow tinkerer. I come here a lot to dig through and get insight from others. (many, many thanks to those who have helped us!) Also, shameless plug, but the film is breath-taking... go rent it if you haven't yet, you won't be sorry. :)
That's a pretty cool website ;)
Basically using some javascript you can detect how far a person has scrolled. Considering the amount of scrolling you can move the contents of your webpage around if their position is absolute.
There are a couple of jQuery plugins that allow you to do simular stuff although I'm not sure you can "scroll through" a sequence of coordinates.
Here are a couple of jQuery plugins that helps you get simular effects:
http://johnpolacek.github.com/scrolldeck.js/
http://johnpolacek.github.com/scrollorama/
http://demos.flesler.com/jquery/scrollTo
http://webdev.stephband.info/parallax.html
I just picked a couple I'm familiar with but there are many plugins that are alike.
edit:
Decided to add some more simular websites for your pleasure.
http://www.activatedrinks.com
http://www.beetle.de
http://www.nikebetterworld.com
the whole page is an "overlay" - a full width and height wrapper <div>. sort of how modal windows do their "full page shadow" effect and have a small div float inside. the whole page content is in that wrapper. the scroll path is a script. the script captures the body scroll and moves the contents of the div accordingly to the positions provided by the script. with a body long enough to be scrollable (which cannot be seen since the wrapper covers the whole page), it's as if you are scrolling sideways, upwards etc.
an analogy is a modal window. the wrapper is the full-page shade. the modal window is the content. and notice how modal windows stick to the middle? that's using a script to calculate it's position to stay in the middle by moving the modal window down, relative to the page's top. but in that website's case, they move in different directions.
It doesn't seem too complicated.
Using the .scroll(function() {}) in jQuery you listen for a scroll event. When triggered you set the position style (left, top) of the content div to give the appearance of moving sideways instead of down.
I guess you'll need overflow:none property on the div to prevent users from scrolling over the area you don't want them to see.
Sounds like a lot of effort for a clunky user interface in my opinion.

Making overlay <div> that stays in position after zoom-resize using HTML-CSS only

I my working on the site that will have image gallery. Designer idea was to make buttons that switch photos be above the photos a bit.
Like this
Example http://img57.imageshack.us/img57/1253/showq.png
Currently I've made a javascript solution to this - it gets position of photo and applies absolute positioning to the button divs. There are some drawbacks - it works unstable in Opera and IE. Also I had to make some dirty haxx to make it stay in position after zooming. I wonder if there is a better way to do this, preferably without javascript.
you mean like here ? (dutch website, see photo browser in the center column at the top)
browser zooming works fine in browsers like firefox and safari because they zoom all the content and recorrect pixel-values. To make zooming work in ie(6) you'd need to style all in em's. But browser zooming is crappy for pixel data anyways…
Absolute positioning of the buttons (left 0 and right 0) is not a problem as long as the container element is positioned relative.
If I understand you correctly, you're trying to center those arrow buttons vertically in relation to the image. This is pretty easily accomplished with just CSS (no javascript required). Here's an example.
The basic idea is that you're using a couple of divs plus some absolute/relative positioning. There's an outer div that drops the top of the whole thing to the center of the parent element and then an inner div that pulls up your content so that the content is centered and not the top of the element.
A popular technique is to split the whole image into two huge (mostly transparent) links. The left half of the photo would take you to the previous image, the right to the next.
Of course you position you images of buttons appropriately and they would move around but I assume the problem you're finding is you have to keep moving your mouse to go through lots of images as the buttons move.... Well with this idea, you only need keep your mouse near the middle, and it should remain over the photo (and therefore a direction).
Example: http://gizmodo.com/photogallery/dreamhomespshop/1008251500
Mouse-over the image and you'll see it's active the complete way across. Not quite the same as your implementation, I'm sure, but the concept applies.

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