I am a junior developer I can't understand how canvas tag is beneficial for us?
I read lot of articles on that but I can't get the root benefit getting from the canvas tag.
Think of the difference between canvas and svg as the difference betwee Photoshop and Illustrator (or Gimp and Inkscape for you OSS folks). One deals with bitmaps and the other vector art.
With canvas, since you are drawing in bitmap, you can smudge, blur, burn, dodge your images easily. But since it's bitmap you can't easily draw a line and then decide to reposition the line. You need to delete the old line and then draw a new line.
With svg, since you are drawing vectors, you can easily move, scale, rotate, reposition, flip your drawings. But since it's vectors you can't easily blur the edges according to line thickness or seamlessly meld a red circle into a blue square. You need to simulate blurring by drawing intermediate polygons between objects.
Sometimes their use case overlaps. Like a lot of people use canvas to do simple line drawings and keep track of the objects as data structures in javascript. But really, they both serve different purposes. If you try to implement general purpose vector drawing in pure javascript on top of canvas I doubt you'd be faster than using svg which is most likely implemented in C.
Basically, thanks to canvas, we can now draw/render 2D shapes using HTML5 and the canvas API.
As an example of what's possible now with canvas, see this
Some possible uses for Canvas:
Image drawing program
Photo editing/manipulation
2D Games
Advanced image viewing such as Microsoft's Deep Zoom
If you can't understand how it's beneficial, then maybe it isn't from your point of view at least. Don't think that because it's there I have to use it somehow, pick and choose what technologies work for you based on what you're trying to build, an Accounting web app probably wouldn't need a canvas for instance.
The canvas will enable you to draw pixel perfect graphics.
The cool projects that came to mind for me are:
Visualize gps data. GPS data is just an XML list of coordinates. You could easily build something in canvas to "connect the dots".
An mobile app where the user can actual sign a document with her finger - canvas allows you to export out the rendered canvas drawing to PNG where it can be saved on the server.
In a game where you have avatars, you can allow the user to actual draw on the avatar. Moustaches anyone?
Other stuff:
In iOS / Android using lots of CSS3
effects like box-shadow can lead to
poor performance, especially when
animating. You can do a lot of these
graphics in a single canvas tag,
here's an example:
http://everytimezone.com/. This thing is flawless on an ipad.
Cool background effects. For example try going to Paul Irish's
site and move your cursor around the
background: http://paulirish.com/
In this HTML5 book sponsored by Google a lot of the effects are using
canvas:
http://www.20thingsilearned.com/ -
particularly the "page flip"
animations.
my personal take on canvas (and when I actually found a use case for canvas) is the ability to color pick and color change per pixel in a canvas element - actually moving the image from something we don't have any information about what is happening inside it to an element like all other DOM elements (and yes, I know about the current problems with canvas and DOM - sure this would be taken care of in the future)
sure - canvas made some sort of animation easier and pluginless, but that we could do before (mostly with flash) - I think the real importance is the ability to know what is happening on the page.
Related
I'll start with the pictures:
Comparison Of Different Publishing Methods From Flash CC
It seems like there is a huge difference between what's published by through Flash CC HTML5 with CreateJS and what's actually created on the program although they are exact copies (I'm not talking about the pose of the character)
The shapes making up the body parts are all triangles with a solid fill and no stroke.
However, in the HTML5 published versions it looks like all those shapes now have a thin transparent stroke around them in between each other.
Any explanation or official support is greatly appreciated!
UPDATE:
The accepted answer definitely improved some of the problem but unfortunately not enough.
Since it's a platform limitation, I decided to work around it by doubling up all the assets of every layer and minutely overlapping them as best as I can.
Here's a link of the work around being implemented if you wanted an update:
link
This is an unfortunate issue with Canvas. The SWF format actually draws lines with fills on both sides, which enables the SWF (and Flash/Animate IDE) to create seamless edges when drawing shapes with edges that line up. Canvas can not do that, so the antialiasing causes the effect you are seeing.
A possible approach would be to cache it at a larger size, and scale it down.
var bounds = character.nominalBounds; // Added by Flash export
character.cache(bounds.x, bounds.y, bounds.width, bounds.height, 2);
The last parameter is the cache scale factor (in this case it doubles the cache size). It will still draw at the expected scale though.
I made a quick sample to show the difference, and it does help. Note that caching is also a good way to get rid of aliasing on edges. You can download the sample here. Uses Adobe Animate 2016.
Plain shapes exported from Adobe Animate
Cached the shape container
Doubled the cache size
You also might want to consider dropping in a shape behind it that is closer to the color of the shapes, so if the edges show through, it is not the dark grey background.
I'm new to the canvas element of html5. I'm specifically wondering when you should put an existing img element inside of a canvas element.
What's the benefit or appropriate use of this?
I've been reading Dive into HTML 5 and didn't quite get what I was looking for in their concluding statement on the topic of canvas:
The simple answer is, for the same reason you might want to draw text
on a canvas. The canvas coordinates diagram included text, lines, and
shapes; the text-on-a-canvas was just one part of a larger work. A
more complex diagram could easily use drawImage() to include icons,
sprites, or other graphics.
An image tag is best used for a static piece of imagery.
Canvas is, to quote the HTML5 working group, "a resolution-dependent bitmap canvas which can be used for rendering graphs, game graphics, or other visual images on the fly."
So, you can slap an image onto a canvas, but that is probably to augment some other piece of work you're creating, like a chart or a game graphic.
UPDATE AFTER YOUR UPDATE
So, if you want to create a really complex chart that tracks stock performance in real-time, you could use the canvas to draw the various bars of the graph, and then also use drawImage() to place company logos on the canvas to indicate which bar belonged to which bar.
Where img does the job, use that. canvas is a very powerful tool indeed, but:
While it's supported by a large portion of browsers today, img is still much more widely supported.
If you need to cater to users with JavaScript disabled, canvas cannot be used; canvas needs JavaScript to operate, whereas img doesn't.
That said, if you need something that only canvas can do, feel free. For example:
Do you need to load an image and then let users warp it or draw on it? A canvas would do quite nicely there.
Do you need to dynamically draw some charts and graphs? canvas would work well there, too.
When you have no need for the more advanced capabilities of canvas, though, and just need to display images, img is the most obvious and compatible choice.
I'm seeking some tutorials, how I make canvas or SVG (not sure which) images in an isometric map for a RTS game purpose. The images should only be clickable on the visible part, otherwise the user should be clicking on the background image. It can either be done by auto detecting transparent areas of PNG or from color overlay. I have no idea which is best.
Thanks.
If you won’t be changing the perspective of your scene, then I would go with SVG because they are DOM elements (clickable out-of-the-box) and you can limit the click area to the non-transparent part of the element. A very good SVG library is RaphaelJS.
The canvas is a different kind of animal. The vectors/rasters you draw on a canvas are not “retained”, meaning unlike SVG, you cannot instruct the box you just drew on the canvas to move. Instead, you are in charge of redrawing that box where you want it. After you draw everything on your canvas, it is basically becomes a big bitmap. If your scene’s perspective will be changing, you might need what canvas does best: speed and flexibility. Using matrix transforms, you can do 2D movement, rotations, scalings and skews. Since you are in charge of the transformation matrix, you can also simulate 3D movement. If your users have non-IE browsers, you also have WebGL which is a full 3D imaging system. With this power comes complexity, so you will probably check out the many game development platforms available for canvas.
With both elements, you can use websockets to do your RTS (of course degrading to long-polling for browsers that don’t support websockets).
I want to start a project where I need to draw diagrams consisting of rounded rectangles connected with lines and a JavaScript action when I click some elements. This needs to work in all modern browsers.
Both SVG and HTML5 Canvas seem to be able to do this so I wonder what would be best.
Also I don't want to reinvent the wheel, so if there are libraries that do such things I would like to know; I took a look at Raphaël and some other JavaScript drawing libraries but they don't give all the functionality I need. In Google's API there is such a tool but it is very limited.
Use SVG because—as a retained-mode drawing API—you can attach event listeners directly to specific elements, and change properties of specific elements and have the page magically update. Further, as a vector-based format, it is resolution-independent.
HTML5 Canvas, by comparison, is a non-retained-mode (aka immediate-mode) drawing API; every pixel you draw is blended with all other pixels on the canvas, with no concept of the original shape. Further, as a raster-based format, you would need to do some extra work to get the drawing commands to adjust for different display sizes.
In general, you should use Canvas if and only if you need:
Direct setting of pixels (e.g. blurs, sparkly effects), or
Direct getting of pixels (e.g. reading a user's drawing to save as a PNG, sampling portions of the image to detect visual overlaps), or
massive number of 'objects' that won't move much or track individual events (SVG can be slow to redraw with thousands of objects).
Note also that you don't have to choose only one or the other. You can draw SVG onto canvas. You can include bitmaps (images) in SVG. You can even include HTML5 Canvas in SVG via <foreignElement>. You can have a single HTML page with multiple layered canvases and SVG elements with transparent backgrounds, intermingling the output of each.
I'm new to html5 and have been playing around with the canvas. I'm wondering when the canvas would really be necessary/useful? i.e. when is it meant to be used?
If i need to do simple animation, like move tags around, do i really need a canvas or is it better/easier to just use jquery/js?
With help of canvas you can create 2D graphic applications, animations, simple transformation of images (like rotating them), GUI etc. Some examples:
Asteroids game
jigsaw puzzle
About GUI, unfortunately I can't load a site, no idea why... it was called iWidgets.com, the only thing I've found is a screenshot. You can see blue pipeline there, they bound elements. It was done with help of canvas; while moving elements, pipelines also were redrawing; when you change active element all its connections changes color to yellow (so you see dependencies). Nice project, I hope it is not accessible just for a while...
Good article about how to use it is here
From "An insight into the HTML5 Canvas Element":
The canvas element is interesting and
worthy of focus because it enables,
for the first time, direct drawing of
graphics within a browser without the
use for an external plugin like Flash
or Java. The beauty of canvas is that
it’s controlled entirely via simple
JavaScript code, meaning it builds on
the powerful functionality JavaScript
already provides and doesn’t require a
crazy learning curve to use.
Choosing to experiment with canvas
over other new elements was simply
down to it’s functionality as a
graphics platform, which inherently
makes it a potentially interesting and
rich platform to play with. It was
decided that pushing the flexible
canvas element would produce the most
interesting results that we can use in
the application.
Another deciding factor for choosing
canvas was to test the animation
capabilities and the possibility of it
being a potential Flash replacement.
Now Flash obviously has features that
canvas could never emulate, however
it’s an exciting concept nonetheless
to see exactly what could be achieved
with canvas that would normally be
done by reaching for Flash.
read that article to get more useful information
PS. If your animation is about tags moving (like parts of your page), then canvas does not fit. Canvas is for graphic rendering. So in that case you will use jquery or other JS libraries.
Here's the best practices for deciding when to use CSS3 Transitions / Animations or Canvas. Keep in mind that if you're using jQuery, under the covers they will be using CSS3 transitions or animations when possible.
CSS3 Translations / Animations - use these if you're animating DOM element styles, such as position and size
Canvas animations - use canvas animations if you're animating something more complex, like if you're creating an online game or building a physics simulator. If you're animating 3-d models, you'll definitely want to use canvas so that you can leverage WebGL
Canvas gives you access to the pixel level of the graphics. If you wanted to do a checkerboard transition you could do that with a script in canvas but not in jquery.
For a few examples of what is possible (already been done) see http://www.netzgesta.de/transm/