html5-game-fundamentals | commons book on building games | Canvas library
kandi X-RAY | html5-game-fundamentals Summary
kandi X-RAY | html5-game-fundamentals Summary
The document object model, as described by Wikipedia is a "is a cross-platform and language-independent convention for representing and interacting with objects in HTML, XHTML and XML documents" 1. Back in Flash, there was a technique called screen invalidation that would mark areas of the screen that needed to be refreshed based on the objects on the stage and how they were moving. The browser handles this process in a similar way. Browser layout engines will listen for changes to the DOM and will repaint or reflow the page accordingly. So what does this mean for writing games? It means that the browser is going to do the work of repainting the screen for you when objects change. This can be beneficial for simple games where there are a few number of elements or updates are happening infrequently. Board, card, and tile games can be good candidates as DOM based games. Another added benefit of building DOM based games is that there is already large number of developers that are currently building client applications entirely in JavaScript. These developers already have the skillset required to start building DOM games without having to learn how to manipulate the canvas element. Canvas is an HTML element that is bitmap based and can be drawn to using JavaScript. A simple analogy is to think of a canvas element like an etch-a-sketch. You can continue drawing to the canvas context, adding detail, until you decide to clear the canvas. Clearing the canvas is equivalent to shaking an etch-a-sketch clean. One issue to note is we will need a separate mechanism to keep track of objects that have been painted to canvas or have been cleared from canvas. This is because canvas only paints to a context; it does not retain any information or properties on that object, such as width, height, rotation scale, etc.
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Trending Discussions on Canvas
QUESTION
Been having issues with this for a couple days, not sure why the text I'm rendering on the canvas is flashing so much. I'm using the requestAnimationFrame() function, but its still flickering.
What I want to have happen is for the text to move smoothly and they remove themselves from the array when they move completely off screen.
...ANSWER
Answered 2022-Mar-07 at 15:51The flickering you are seeing results from your looping code, where you skip elements of the array when deleting elements (Element 3 needs to be deleted? You call splice(3, 1) and then continue with the loop at index 4. Since the array shifts when you call splice, you should process element 3 again).
The imho easiest way to fix this is to iterate backwards over the array. Please note that iterating backwards is less CPU cache efficient (because every array access leads to a cache miss), so another fix would be
QUESTION
Does anyone know why transparency drawing on a Canvas works perfectly fine using drawImage(), but doesn't work at all with a PixelWriter? I initially thought it may have something to do with Blend or some other mode/setting on the canvas/context, but haven't had any luck with that yet.
I need per-pixel variable transparency, not a single transparency value for the entire draw operation. I'll be rendering a number of "layers" (similar to how GIMP layers work, with optional transparency per-pixel). An additional open question is whether I'm better off first drawing the FINAL intended output to a WritableImage and then just drawing to the Canvas, for performance reasons, but that seems to defeat the point of using a Canvas in the first place...
Below is an example which shows a partially transparent Color being first drawn to an Image and then to the Canvas, and directly to the Canvas with setColor(). The transparent area is the Image draw, the opaque area is the setColor part. How do we get setColor() to respect Color alpha transparency for each pixel?
...ANSWER
Answered 2022-Feb-21 at 20:51The GraphicsContext begins with the default BlendMode, and all forms of drawImage() use the current mode. In contrast, PixelWriter methods replace values, ignoring the BlendMode.
The example below lets you experiment with the supported BlendMode values to see the effect. Related examples are shown here and here.
QUESTION
How to get transform matrix of a DOM element? Just like canvas context, do we have a getTransform() method on DOM?
...ANSWER
Answered 2022-Jan-14 at 11:42getComputedStyle($el).transform should return a 2 x 3 transformation matrix, IF there is any 2d transformation, and 4 x 4 matrix3d if there is transformation on the z axis too. See my answer here for how to manipulate that in case.
In case of nested elements, the resulting matrix is the multiplication of matrices starting from parent to child:
QUESTION
I'm following the WebGL tutorial from MDN (code, demo (black rectangle)) to create a WebGL canvas.
The goal is a userscript (with WebGL shaders, i.e. video effects) for YouTube. So I opened a YouTube video page and put the code below (from the link above) into the JavaScript console. The canvas got created, but it is invisible.
The canvas inherits a lot of CSS from YouTube by default. Am I overlooking some CSS properties that make it invisible? What to look out for in such cases? It should be black.
...ANSWER
Answered 2022-Jan-04 at 02:19Your canvas is there, but it's not on-top. Set some additional CSS for positioning. For example:
QUESTION
I need to create circles in canvas using fabric. Every click, there is a circle created. However, if the new circle created it will replace old circle. This my stackblitz demo.
HTML
...ANSWER
Answered 2021-Dec-30 at 04:14The problem is that you're repeatedly creating the Canvas object, which is likely resulting in the canvas element being drawn over multiple times in separate instances. That is, every new instance will only ever contain the most recent circle and will draw over the previous instance. What you want to do is create the instance once and then reference that instance each time moving forward.
In your code snippet above, it could look something like this:
QUESTION
I have a task where I need to place rectangle on area where I clicked on cavnas (PDF). I am using React and after I upload pdf file by using react-pdf module that file is being translated into canvas element. I want to remove previously drawn rectangle after I click multiple times so that rectangle is going to change place it is not going to be repeated on screen. What I tried so far is this:
After I choose pdf file that file is being translated into canvas and viewed on page using react-pdf module that I mentioned earlier
...
ANSWER
Answered 2021-Dec-12 at 19:05Here's a self-contained and commented example demonstrating how to get a rectangle of ImageData from a canvas, store it in React state, and then restore it to the canvas in-place:
I used TypeScript when creating the example, but I manually removed all of the type information in the snippet below in case it might be confusing to you (your question didn't indicate that you are using TypeScript). However, in case you're interested in the typed version, you can view it at this TS Playground link.
QUESTION
As a frontend starter, I've just started to learn canvas. I'm trying to draw some text. But the size of canvas could not display correctly at once: My code for creating canvas:
...ANSWER
Answered 2021-Dec-07 at 14:30There are a couple of thing you need to do:
- call measureText after you set the font or the width will be incorrect
- after changing a canvas dimensions you need to reset the font
On your code you will need to set the font twice.
First before we measure, Second after we change the canvas width and height; I added a console.log to my sample you can see that after canvas change dimensions the font changes to default;
Here is a working sample:
QUESTION
I am trying to write a JavaScript function that removes items from an array to reach a defined length. The function should eliminate the "gaps" evenly through the array. I need this function to simplify polygon vertices for canvas drawing.
This is how it should work:
This is the code I came up with:
...ANSWER
Answered 2021-Nov-27 at 22:43If you just want to eliminate items to cut that array to a desired length. Use the Array.splice() function.
So if your desiredLength = 3 for example. And you have an array = [1,2,3,4,5].
array.splice(0,desiredLength).length == desiredLength should be true.
QUESTION
I have a simple HTML canvas that covers the entire page which displays fine by itself.
ANSWER
Answered 2021-Dec-02 at 20:39This is unrelated to and the behavior is the same with any other block element such as a
If you set the lone element in the 's dimensions to innerWidth/innerHeight and the parent has no padding or margin, then you've used up exactly all of the space on the page and no scrollbars are necessary.
If you add a
innerWidth, as the docs state:
innerWidthreturns the interior width of the window in pixels. This includes the width of the vertical scroll bar, if one is present.
The original element set to exactly innerWidth pixels now overflows the screen horizontally by the width of the vertical scrollbar. Therefore, a horizontal scrollbar becomes necessary.
An option you can try is document.documentElement.clientWidth. As the docs state:
clientWidth[...] includes padding but excludes borders, margins, and vertical scrollbars (if present).
(you might need to click 'full page' after running the snippet to see the difference):
QUESTION
I am really new to Vue and for this project, I was trying to load canvas inside a div. If the canvas is loaded outside of a div it works correctly but I want to display a canvas if loadModal is true only. In this code I have used two canvas one is inside div and other one is outside of div. It loads canvas correctly outside of div only. Is there a way to load canvas inside div as well? Here is my code below on JsFiddle
JsFiddle Code = https://jsfiddle.net/ujjumaki/6vg7r9oy/9/
View
...ANSWER
Answered 2021-Oct-11 at 18:31Try with v-show and with class instead id, so you can select all divs:
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