I am developing a website with React which has what we called "snippets", basically a modal window displaying some kind of media (audios, videos, slides, text quotations, pdfs). These media have "positions", as a page number, an image number, a playback position, or a scroll position. If she likes the user may store these snippets together with their positions in a "locker" and come back later to whatever is in there. Visually the locker will hold a "thumbnail" of the snippet representing the appearance of the snippet at the time of storing it. My question is how to go about making such a on-the-fly thumbnail. Two approaches come to my mind, however, if you have other ideas I am eager to hear them.
Component approach: Since I already have the component, I could reuse or rather clone it, scale it down, disable it for mouse interaction. Would React.cloneElement() be the way to go?
Advantage: Easy to do.
Disadvantage: Too many duplicates of potentially resource-heavy components may slow down website. Styling may become non-trivial as some embedded media (audio, video) bring their own potentially inaccessible styling with them.
Image generation approach: Since I only need an image, I could take a screenshot of the snippet area, scale it down and use it. Can this be done fully (from generation to usage) on the client side? Is there a good library which does the heavy-work for me?
Advantage: Resource-heavy only during the making of the thumbnail, resource-light in the locker. Accessible for any styling.
Disadvantage: Potentially difficult to do?
After some research I found a solution. Interestingly, it is a mixture of the two approaches I was able to think of. It is possible to access and rasterize the DOM elements which make up the snippets, draw them on a canvas and turn it into an image. The most popular library for this seems to be html2canvas, however, there are a number of others among which rasterizeHTML and html-to-image seem to stand out. Often wrappers for React exist, in the case of html2canvas, for example, use-react-screenshot.
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So I'm building a portfolio and sales website for a painter (my wife) based on WooComerce (WordPress). This is a side project that I have plenty of time to finish. I want to build a live/moving photo wall, with perspective. The following photo will give you a (albeit, very rough) idea.
Basically, I want to start off with 16 images (the number is actually arbitrary), apply perspective to them and allow the visitor to click any of the pics and go to that images associated page. Now, after a given time, I want new photos to show up.
I'm not particularly concerned if I flip these pics, randomly, like tiles to introduce new ones OR if a column slides off and a new column is added (i.e. the adding of 17-20 in my picture). This is a semantic difference in the way I build this code and isn't part of my question (I don't think). All of the original pictures are going to be square and will be uploaded by the user, whom we assume is of novice/intermediate computer experience.
So my question is about the approach. Do I:
Make my wall script (likely using jQuery and HTML < map > and < area >) take care of the flipping and linking, but the perspective and scaling is done and cached on the backend.
Every image I upload to the server, for the photo wall, run it through a ImageMagick script that will transform (i.e. apply perspective of the largest size for the wall) and then scale it down for the other columns using a naming convention like: orignalthumnail_marilyn.png perspective0_marilyn.png perspective1_marilyn.png etc. (with the number for the different columns, relating to the scaled sizes). This is will be harder on bandwidth (maybe not, if compressed correctly) and easiest on the user's hardware (assuming non-mobile).
Use Javascript & CSS (and possibly HTML5) to do everything. I load the images into and use the CSS3 skewed/transformed < div >s, JS to flip/moves the tiles (I could do CSS I suppose). I feel that this option is the worst, as far as looks. This is because CSS clips horribly using the transform attribute (on my browser, FF 30) (I also made a quick demo at http://jsbin.com/febatohi/2/edit). Also, it requires the user's hardware to be able to handle all of the transforms, which is not always appreciated online. Maybe there is a way to handle this with a JS library I'm not aware of.
Use Flash. This is my least desirable option. It requires me to either not build this myself or pay someone else (pfft!) or that I acquire and learn Flash from Adobe (I said time wasn't an object, but patience can be). However, it can produce the best looking result, as I have seen things done similarly to this is Flash. It also is a middle ground of hardware and bandwidth, but to me the most time consuming and also limiting to those browsers and users who use Flash (though I feel this is only a small percentage of users).
Other suggestions?
I'm developing an iPad app using PhoneGap and jQuery Mobile and I'd like to create a preview pane in a carousel. The preview pane would include a smaller version of each of the other panes, scaled so they fit inside the single pane. The panes are not static and can be updated at any time using WebSockets, and the preview should be updated simultaneously. There can also be any number of panes (although to keep things simple, assume an upper limit of 9). For performance purposes, assume each pane can have upwards of 200 DOM objects attached to it. To make it slightly more complicated, the carousel can exist on more than one different page.
I've been contemplating the best way to go about implementing this preview pane, and, before inventing a pair of Complicator's Gloves, would like to hear back from the community on any possible better strategies.
A couple methods I have been considering include:
Cloning each pane and then using a CSS transform to scale it to an appropriate size, based on how many panes there are, and then attaching the clones to the preview pane.
Store each pane as a jQuery object in a variable and draw each pane and the preview pane using that object (possibly necessitating redrawing the entire carousel every time there is an update, depending on how much effort I want to make identifying and updating deltas).
Repositioning all the panes so that they exist inside the preview pane when the preview pane is active (this might break the carousel, or at least make it look slightly bizarre as a user swipes a pane over but hasn't actually moved on to that pane yet).
Is there anything I'm missing? It would be nice if there was an easy way to "link" two elements together to make one mirror the other, but apply different CSS to one or the other (for zooming). I suppose it might be possible to do this by creating an event that would fire and then adding a listener to its clone, which would then copy the html of the updated element to itself (probably wouldn't be too terribly to difficult to write a jquery plugin to manage this).
Any better suggestions?
I am not sure what phonegap allows for as far as rendering options go, but my first instinct would be to take a screen shot of the relevant pane. Perhaps phonegap has this built in?
Another option is a javascript library which will clone the DOM and create an HTML5 canvas element. You can either then display the canvas natively, or convert the canvas data in to image data.
Here is one such library: http://html2canvas.hertzen.com/
Given the large number of elements needed, I would hesitate to clone those over and over again. However, if live previews are a necessity, that might be more efficient than using image files or the canvas. You could fire off the canvas draw function after major changes, but probably wouldn't want to do it after the end of every frame of animation.
I'm making an TV Guide. See http://i.tv/guide for an example implementation using Canvas.
I need to make lots of little boxes representing each show. I need to be able to scroll them around, both vertically (channels) and horizontally (time). To make it with Canvas, my understanding is that the only way to implement scrolling is to intercept the correct events, and redraw the canvas smoothly with new offsets many times a second.
If I were to use divs, I could slap scrollbars on it and let it scroll normally. I could position them once, and let the scrolling move them around, rather than re-calculating their new offsets.
Which should I pick for this kind of project? If I use divs will it be too slow? Some lineups have 500 channels. I want to display up to 4 hours at once.
Thanks!
I would strongly recommend using plain HTML in preference to canvas, for interactive elements. Apart from the speed issue (divs are usually going to be faster than drawing it all manually yourself), HTML is designed to offer accessibility and usability features for free, which you'd have to do a lot of work to get even partially from canvas.
The canvas-based guide as linked has the following drawbacks:
very slow to render/scroll, for me;
impervious to keyboard navigation;
no HTML link actions (like middle-click-link-to-open-in-new-tab or right-click-bookmark);
text not copy/pastable;
a dead loss for accessibility tools like screen-readers;
reduced browser compatibility;
invisible to search engines.
Use canvas for pretty graphical and interactive effects you can't achieve with plain HTML. To be honest I don't even see any of that on i.tv's site; I have no idea why they have implemented it in this seemingly-crazy way.
Doing it with DIV's wont have issues with speed. Browsers rendering engines are built to render elements. DOM rendering is faster than canvas rendering in a lot of cases, take isogenicengine they use DOM based rendering to render thousands of elements to make games You should implement it based on your technical ability. Both technologies will be able to do what you want. Personally I would choose canvas but I see no issue with DOM rendering.
Good Luck.
My demo is here.
Basically, I have a HUGE image (19160px × 512px to be exact, just under 2MB) that I transition the backgroundx using javascript to make it appear as if a transformation was happening.
I cannot compress the image much more without ruining its quality dramatically. Is there another way that I can achieve this with the same level of cross-browser and not rely on plugins like flash, but have it load faster?
Have you considered making this a video?
It might improve loading time somewhat.
Also, another idea. Have you tried using only the first and last image, putting the last one on top of the first, give it opacity:0 and fade it in using JavaScript (e.g. jQuery)?
The effect won't be 100% identical to what you have now, but it might look good enough to please the client, and it would reduce loading time to a bare minimum.
If both ideas won't work for you, I think the first 10-12 frames could be compressed more effectively as GIF images. (It's an estimate, I haven't tried.) You would have to split the image into multiple div s to do that and change the method you use to switch the images, and you would have more requests, but it could be worth it.
If it is a jpeg, you can always use progressive encoding. it will become clearer as it is downloaded.
There is also an interlaced
"Progressive JPEG" format, in which
data is compressed in multiple passes
of progressively higher detail. This
is ideal for large images that will be
displayed while downloading over a
slow connection, allowing a reasonable
preview after receiving only a portion
of the data. -Wikipedia
Slice it like Google Maps.
If you want to change that many pixels on the screen at once, you'll have to get them to the client somehow. You could chunk it into multiple images and use something other than background-x, but then you expose yourself to other potential network interruptions along the way.
The only alternative I can think of to precomputed images like this one is to do the computation on the client - start with the full-colour image and manipulate it using the client's CPU. Your options here involve canvas or CSS3 or a plugin.
I'm not a big fan of Flash but in this case it seems like the right tool for the job (unless you need it work on the iPhone). If you don't have the Flash authoring tool you can use the free Flex compiler.
See http://www.insideria.com/2008/03/image-manipulation-in-flex.html
Make it into an animated gif? Break it up into individual parts to remove all the area that is obscured by content.
What is the best cross-browser way to get a flat mouse coordinate input data and simple callback for mouse events for my rectangular game area on my web page, even when it has loads of larger and smaller images and text string overlaid haphazard onto it?
And what is the best way to insert or remove a text string or semi-transparent image overlay at an arbitrary location (and Z order, specified relative to existing objects) in a board game rectangle with cross-browser DHTML?
And how can I stop the user selecting part or all of my montage of images (I just want them to interact with it as if it was Flash), and can I stop the right click menus coming up in IE, FF etc?
I want to do this without Flash because I want something that will work both on desktops and on iPhone and potentially other mobile platforms too.
I appreciate there are serious limitations (eg less image scaling capabilities, not vector, no rotation capability) to what I can do if I'm not using Flash but I'm very interested to know what capabilities are available.
Are there perhaps any frameworks available to make it easier than coding from scratch?
Would J/Query be a good match for some of the requirements? What else do I need?
I would recommend Google Web Toolkit. It lets you program in Java, which gives you all the type-safety and nice IDE functionality that Java entails, but compiles to Javascript so that you can just run it in a browser. It also does a ton of optimization and supports tons of features.
jQuery is excellent at doing this. I used jQuery's UI and Ajax functionality to implement the frontend for a game of chess.
I made it a little easier by creating an 8-by-8 table with unique div names for each tile, so Javascript can access them by getting the elements by id. If you can't create something like that, you do have the option of placing elements anywhere on the page (either absolute or relative to a given element). You can also easily change the z-index, including when the use is dragging a piece or when they have dropped it.
As far as disable right click and item selection goes, that's something that I didn't figure out how to do. You might want to take a look at some other Ajax games like Grand Strategy, which are much more polished than my experiment and may have figured out how to do this.
There are two main APIs for working with arbitrary drawing and positioning on the web, Canvas and SVG.
Take a look at Chrome Canvas Experiments and the Raphael Javascript toolkit to see some examples and Javascript abstractions.
The key is element.style.position = 'absolute'. To illustrate just what's possible here's how far I've managed to push javascript (and from scratch at that!):
http://slebetman.110mb.com/tank3.html - RTS in DOM! Click on units/squads then click somewhere else to tell them where to go. You can control both sides.