I am using KineticJS and wish to create a precise image hit region (ignore transparent pixels) for my sprites. I see how createImageHitRegion accomplishes this for images, but I don't see how to apply this to sprites. Said another way, while method createImageHitRegion is a method which accomplishes what I want for images, there appears no similar method for sprites. If I could create an image hit region on just one image of each of my sprite that could work for me, but a big rectangular region which encompasses the entire width and height of the image of the sprite can't work. Any ideas for a workaround? Perhaps I've missed something?
There's no easy way hit-test non-transparent pixels on sprites.
I can think of a couple of theoretical workarounds...
If you can draw a path outlining the pixels you want to hit.
The sprite object allows a custom drawHitFunc so you could use mySprite.afterFrame to redefine a custom hit area for each of your sprite images.
mySprite.afterFrame(0, function() {
mySprite.setDrawHitFunc(function(){
// draw the path you want used for frame#0
});
});
// repeat for all frames
If you can't draw a path outlining the pixels you want to hit.
Instead of using sprites, make your own sprites using individual images.
Do that by creating a series of images (including createImageHitRegion) and sequentially making one of those images visible so it appears to be playing a spritesheet.
Related
I am trying to draw some guide lines via fabric.js like the online editor app on printio.ru.
So far, I placed 2 canvases with the same size in one page, the top one is to be a static workcanvas which used to draw some guide lines and the bottom canvas will contain some interactive objects. This seems to be how they do it in the page on the link above.
However, I can't work with those objects on the bottom canvas because the top canvas interrupts mouse events. Is there a way to let the mouse events to pass through to the bottom canvas? I am thinking of something like canvas.mouseenabled=false on the top canvas - is that possible?
I have thought of an alternative solution: place the guide lines and other objects in one single canvas. I don't like that solution because it adds things that I don't want to the bottom canvas and, in that case, I have to add some line instances instead of just draw line by context2d, which I think will give me low performance
Apply css-property
pointer-events:none
to upper elements, mouse events can through.
https://developer.mozilla.org/en-US/docs/Web/CSS/pointer-events
It will be work for modern browser.
http://caniuse.com/#feat=pointer-events
As the title says, i want to add background pattern to a png image(not the whole canvas). I tried various guides but they are all about adding background pattern to whole canvas by either using background-image css property or by using canvas's createPattern method.
This is what i'm creating.
As you can see, there are various png images on the canvas(left arm, right arm, body, etc.) and they are all customizable. Now i want to add repeat-pattern to those png images. Those repeat pattern would be an image itself.
How to do that via svg, fabric or any other method?
A really simple way is to create a FOR loop to draw your PNG images at the size you need.
Use the canvas width/height values,your image size and your preferred image distance to determine
the number of iterations your loop needs to run.
On each iteration increment a distance variable a certain value in
order to blit your image at an increasing distance on the x/y axis.
When the loop ends you will have a pattern.
I have big horizontal strip image in photoshop which is made of lots of smaller elements. The background is transparent and the strip goes from smaller elements (left) to bigger elements (right). My goal is to make this strip interactive to mouse events.
Each element is some kind of polygonal image which is trimmed left and right and then exported as a png. It is then imported into a canvas.
The problem is that I can put them side by side but since they are not rectangles I need a way to calculate the offset made up by the transparent pixels on each side of each element to make them stick together correctly... I am using KineticJs to get a precise hitarea for each element... So maybe there is a way to do it automatically with kineticjs,or there is some kind of operation I could do using each image data?
My problem illustrated:
Any ideas?
Also I am doing this simply because I would prefer precise mouseOver bounding box on each item (rather than a simple rectangle) and would rather avoid the solution to calculate each offset manually... But maybe that's not worth it?!
Ok, so you have yourself a custom shape you want to use, here is a tutorial for that: http://www.html5canvastutorials.com/kineticjs/html5-canvas-kineticjs-shape-tutorial/ , the simplest thing you can do, and even that seems fairly long, is to calculate the bounding lines for that shape. (Two somewhat vertical lines, and two somewhat horizontal lines). Then you test if the right vertical line of shape one crosses with the left vertical line of shape two, if they do, then set the coordinates of the images to be the same coordinate.
http://www.mathopenref.com/coordintersection.html
line1 = ax + b ..... line2 = cx+d //see possible tests
if(...intersection test...){ // or just test if some coordinate is left of some other coordinate
shape2.setX(shape1.getX()+shape1.getWidth()); //account for image width, so they don't overlap
shape2.setY(shape1.getY()) // no need to account for height
}
UPDATE: This is a very rough solution to the workings of the problem. The next step would be to do more fine tuning dependent on each image.
http://jsfiddle.net/9jkr7/15/
If you want precise areas, use an image map. With some clever finagling and a blank image gif you should be able to have the background you want whenever you hover over any particular area of the image map (might require javascript).
The other option I can think of would be to use SVG itself or one of the many libraries in existance to build interactive vector graphics into your page.
You could also write a function that calculates the left most, top most, right most, and bottom most pixel by looking at all of the pixels in the image data. Here's a tutorial on that:
http://www.html5canvastutorials.com/advanced/html5-canvas-get-image-data-tutorial/
Usually when an image is being resized in javascript or css3(using background-size), it will stretch an image from the center point. I need an image to be stretched and distorted from a single point that could be anywhere. It's going to be dynamic so I don't want to resort to using separate images.
Here's a pic that illustrates what I mean:
Hopefully there's an answer out there!
You have a few options to achieve this effect.
The "correct" way would be to use canvas to draw the image: Skewing images individually using canvas
Another way would be to fake the effect using the CSS transform skew.
http://developerdrive.com/demo/skewing_elements/skewing_elements.html
You would do this inside an element with "overflow: hidden" to make it look like a background image.
It's not even clear to me what you want from the image you're linking too. Do you want it distorted or not? And is the distortion uniform?
I'm going to guess whatever you're doing can be approximated by drawing an ever decreasing set of (or maybe rectangles) clipped from the center of a some image and drawing them onto a "canvas" (think generic term not html5 term) given new coordinates for the center of each clipping. There may be a faster way to draw this than redrawing parts of the image multiple times, it's just how I visualize it possibly working.. at least maybe in some mathematical sense.
What I am trying to make is some kind of scrollable viewport in which a really large image is loaded (as in 10.000 x 10.000 pixels or more) and I should be able to draw some lines / shapes on this image.
There are two methods I can think of to draw the image / allowing the shapes to be drawn:
Using an tag to draw the image and draw a canvas the size of the image above it.
Using the drawImage() method to draw the image and just use a canvas.
I have tried both cases but when I load an image (in the img tag or using the javascript Image() object) it consumes about 500MB of memory.
I am wondering if there is a more efficient way to accomplish this.
Never ever make a user download an image that size unless you absolutely have to.
Make 100 smaller tiles (or thereabouts) of the image and draw the tiles to the Canvas, only drawing the tiles that can be seen at the current time (like google maps, etc do).