I'm making a very simple page which needs to do the following:
There will be a map, which is a background image in a div, and there will be some clickable images distributed on the map (each within a div of its own). The images, when clicked, should make some markers on the map appear or disappear, to indicate positions where that can be found on the map.
It's not supposed to be fancy, it's just supposed to work and be doable quickly (I'm inexperienced and don't have much time). What would you suggest?
I tried to find a way to do it with just css, but the best I can do is a very raw and impractical way of doing it, nothing simple and elegant. I'd like to avoid using any libraries, if possible.
Do Something Like This
document.getElementById('a1').addEventListener('click', toggle);
function toggle(a){
document.getElementById("i1").style.display='block';
setTimeout(function(){
document.getElementById("i1").style.display='none';
},500);
}
Fiddle:
Fiddle
Related
I'm trying to build myself a very simple framework to manage drawing content to the same webgl canvas via multiple views and react. I want to able to use the same resource in different areas of the window, so i'm trying to avoid using multiple canvases.
The end result should be something like this example from three.js.
I'm pretty confused with how to manage this from the html side and am struggling to figure out if any limitations of this approach should be considered.
<WebGLContext.Provider value={contextState}>
<canvas ref={canvasRef} style={canvasStyle} />
{children}
</WebGLContext.Provider>
This is my top level wrapper. With this, i can instantiate a <WebGLView/> wherever and get the rectangle to be used as the "viewport" into the canvas. Just like in the example i scissor out that rect and draw some content there. Because my entire react app renders on top of this, i can put any content over that view. But... i can also obscure it. This only works if divs above it are transparent, or there is hardly any overlap between these viewports.
The view is something like:
<div ref={viewRef}>
{children}
</div>
Another approach that i had in mind is to use react portals to manage another layer, above the canvas.
Something like this:
<WebGLContext.Provider value={contextState}>
{children}
<canvas ref={canvasRef} style={canvasStyle} />
<div ref={aboveCanvasPortal}/>
</WebGLContext.Provider>
Since i know the rectangle of the viewport for my webgl drawing, i can manage the html above it in a similar way, draw an absolutely positioned div in it, and put some UI content in there. This also doesn't feel like it would scale very well, but i could at least have a scrollable column with a background color, a webgl view in it, and some ui on top of it. Overlapping components would probably crash this.
The view is something like:
<div ref={viewRef}>
{ReactDOM.createPortal(children, aboveWebgl)
</div>
I've been thinking of using toDataURL() and then passing it as an image background to the views. This seems like it would solve the stacking/overlapping issue, and i could have a very simple html structure. But this is also a tremendous amount of overhead to add to webgl? If so, is there a way to do it cheaper, since the browser has to compose all of this somehow anyway?
Use case wise, my main use case is to use it with something like react-mosaic, where i just have a bunch of rectangles, very flat within one viewport, a div or the window. The second approach feels like it would work best. And then perhaps if i put a modal on top of that, creating another layer of below,canvas,above, html, would make sense, but like no more than that?
When taking a deeper look into the code of the three.js example you have provided, you will note, that there's just a simple <canvas id="c"></canvas> without any wrapping at all.
The key to your question is not to think primarily about viewports, but about Scissor Boxes -- as used in the aforementioned example in its function render(). If you prefer (like me) to use raw WebGL instead of three.js, take a look at the MDN Doc on WebGLRenderingContext.scissor() and on basic scissoring as a starting point.
That should reduce the complexity of your problem and return it back to the level of (a more performant) WebGL, instead of trying to patchwork on HTML level.
I have to place on a web page a cylinder that looks like this:
it is composed by small images that overlaps to draw the curves on the surface. Every one of them is places on the page with a different img tag enveloped in an anchor with its own href. The z-index property of the img is used to make them overlap in the right way.
The cylinder has to be composed because it is dynamically created, as you can see from the image, its faces can have different colors.
What i need to do is to make all the faces clickable and each one has to point to a different URL.
My problem is, of course, that the cylinder has curves. And i have to be sure that the clicks points to the correct URL especially near the curves, it hasn't to be precise at pixel level, but at least acceptable.
I've tried to use a map with a single area for each of the images that composes the cylinder, but of course it didn't work, as i saw from the specifications, in such cases only the first declared map in the DOM works.
I'm thinking about to solve this via Javascript, but i think it wouldn't be an easy job, so i would be happy if someone can give me some advice on what should i try.
Oh, i cannot use HTML5 features to solve this.
Neat application of older technology to solve a challenging puzzle.
I can think of two ways forward for you. One is to put a transparent (rectangular) image on top of the cylinder and create an HTML image map, using the shape="poly" attribute. For resources, search for the HTML elements map and area for reference, especially the shape attribute. There should be many good tutorials online. Nowadays this technique isn't used that much any more, but it was really popular in the late 90s.
Another way is to use event delegation in javascript, attaching an event listener to the primary container. On each of your image "pixels" apply a CSS class for the appropriate portion of the cylinder it is in. In your event handler, you can do something differently depending on the class of the clicked on image, and you can do this without the massive overhead of attaching an event on each individual "pixel". In JQuery this would be something like:
$("#cylinder").on("click", ".green", function() { location.href = "green_url"; }
$("#cylinder").on("click", ".red", function() { location.href = "red url"; }
assuming you put class="green" on your green pixels and class="red" on your red pixels. (You can do this by quadrant or other technique; color is just an example).
Your best luck SVG ! https://developer.mozilla.org/en-US/docs/SVG/Tutorial
It is almost impossible with html dom elements to do this, you will have to bend it with CSS compatible all browsers.
There is also Canvas but you will have a hard time dealing with the clicks.
Only problem with SVG is that it's not supported in < IE8, and hardly in IE8. But bending a DOM element is also not available < IE9.
EDIT:
I saw that you can't use HTML5, so your only chance is generating the whole image in GD2 for example and trying to map the points. But what is the reason you can't use HTML5 ?
You might also try doing it using javascript / canvas via getImageData() function. This canvas function will rgba values of the given point. Using the alpha value you can check if mouse is over or clicking on the correct area or if it is a transparent area and nothing should happen.
I also made jquery plugin exactly for this purpose. Maybe it might help. http://www.cw-internetdienste.de/pixelselection/
Starting out with a given image, I would like to be able to trace polygons on the image and then export the result as an HTML image map.
What would also be nice is to be able change the scale of an existing image map, thereby changing the size of the polygons and shapes.
Is there a program that anyone knows of that has these features?
Many program do this. It is to time consuming doing complicated maps manually.
I know coffeecup is a used tool for this.
What would also be nice is to be able change the scale of an existing image map ..
I wrote a Javascript image map resizer, it's here. Just paste in your HTML and it will return the scaled image map. You must include "height" and "width" attributes for the original image in the HTML. (This is a quick and dirty tool, it doesn't actually do anything other than parse the HTML you've pasted in. It uses those attributes as the base of calculations).
You may also be interested in my jQuery plugin ImageMapster which can resize image maps dynamically among other things.
I use this site it's fairly good for quickly making image-maps
I use this site https://www.image-map.net/ to trace polygons on the image and then export the result as an HTML image map.
I'm using GAE Java and GWT together on a website which is primarily a large map with basic infowindows. I want to customize my info windows and I know how I want them to look-- but making this become a reality proving itself be tricky. Here's what I want it to look like:
Whenever a marker is click, a new info window will appear a few pixels to the right of the marker. The overlay will animate onto the screen, growing from nothing to about 300px by 300px. This overlay will contain information injected from the GWT portion of the code and will have a button to close the div in the top right corner.
Writing this in plain JS or jQuery would be no problem for me, but what I'm having trouble deciding is how and where I should inject the div into the proper position ON THE MAP CANVAS? Once i understand how I ought to do this, I believe i can finish the rest of the work myself.
Thanks so much!
probably too late for an answer but for anyone else who'll end up here,
the following link should get you going
http://blog.mridey.com/2009/09/label-overlay-example-for-google-maps.html
Here's the thing: I have a Google Map with a lot of markers in it.
The problem is that the map loads, stays empty for a little while and only then markers are displayed. The markers are customized PNGs.
My idea is to "preload" them (not sure it's the right word) so they appear almost at the same time as the map.
What I did so far is to add the same images I use on my map, outside of the map, earlier in the page in display:none;
I'm not sure but it seems like the time between the map and the images are displayed has been reduced.
Is it the best way to do it, and is it a good practice?
You could use "sprites" i.e. a collection of separate images on 1 single png. This bears the advantage of requiring only 1 load i.e. less separate loads. Google GWT pushes this technique a lot (i.e. Image bundles).
The value of this technique increases with the number of discrete images that require loading: the more separate images, the longer it takes to load them.
Don't use display:none for preloading. Because an element set to display:none doesn't render any of its physical attributes, the browser doesn't bother downloading it until it's made visible.
An alternative is to use visibility:hidden, but you run the risk of running into a user agent that does pretty much the same thing. visibility:hidden requires that the browser compute the box model for the image, which requires that image is loaded (to get the dimensions). I don't believe this works in IE6, though.
The last technique (and my favorite) is to create a div directly before your </body> tag. Position it absolute with left: -99999999px; top: -99999999px. The browser is forced to render the images (and consequently load them) and there's no messy Javascript to deal with.
Now, to integrate this with your issue, put the code for your Google map after your "preload div". Your browser will be forced to load the images before it runs the code to create the map. This should solve your problem.
Hope this helps!
From what I recall of most modern browsers, images are always loaded once (given the src of the image is the same). I guess you mean loading them before the maps load.
In my opinion in does not really matter that much. Markers should be relatively light compared to the map image itself and I can't really use them without the map anyway.
If you think it improve you user experience then I think it is a good practice, but I'd try to get them on a more cleaner way, probably an ajax call early in the page load?
Take a look at Ajax In Action: Preloading Images