lucky-canvas | 基于 TS Canvas 开发的【大转盘 / 九宫格】抽奖插件， 一套源码适配多端框架 JS / Vue | Canvas library

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?

How to get transform matrix of a DOM element? Just like canvas context, do we have a getTransform() method on DOM?

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.

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

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:

1. After I choose pdf file that file is being translated into canvas and viewed on page using react-pdf module that I mentioned earlier

   ...

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:

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:

I have a simple HTML canvas that covers the entire page which displays fine by itself.

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/

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