What I'm trying to get done in the example shown below is a pie like shape for a preloader script. The deal with it is that it starts on 0% and finishes on 100%. Depending on the % given the circle behind the gray circle shall fill it self up.
Currently i have the shapes in 2 different canvas's as i had to use clip to actually hide parts of the circle. But as this applied to my overlay with the gray circle i spliced them up. They are by the way both images.
I would really appreciate any effort that you guys put in helping me.
Been trying to solve this issue for ages.
Found the solution.
Seems like i had to use the moveTo
function in order to get the shape to be painted correctly.
Using the
function degreesToRadians(degrees) {
return (degrees * Math.PI)/180;
}
function to use degrees rather than Radians.
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Hope this helps someone else :)
Related
The problem: I'm trying to create a simple drawing app using p5.js. Instead of the standard cursor image, I'd like to show a circle at my cursor location that represents the size of the drawing brush.
Potential solution 1: Replace the cursor using the cursor() function native to p5.
Why it doesn't work: The p5 cursor function only takes the following parameters:
ARROW, CROSS, HAND, MOVE, TEXT, or WAIT, or path for image
As such, there's no native way to replace the cursor using the ellipse class.
Potential solution 2: Use the noCursor() function and then draw the circle at the cursor location, while also drawing the background, as such:
var brushSize = 50;
function setup() {
createCanvas(1080,720);
noCursor();
}
function draw() {
background(100);
ellipse(mouseX,mouseY,brushSize);
}
Why it doesn't work: While this solution gets the desired effect i.e. replacing the cursor with a circle the size of the brush, the constantly updating background prevents me from actually drawing to the canvas with the brush when I want to.
Is there some way I can replace the cursor without actually drawing the ellipse to the canvas? Is there any way to save and then instantly reload a canvas in p5? I couldn't find such a method searching through the API docs. Any hints are appreciated.
According to the reference, you can pass a URL into the cursor() function to set an image.
If you want to use an image that you draw, you're going to have to draw them ahead of time and save them to files, and then use those files. Something like this:
cursor('images/ellipse-15.png');
Where ellipse-15.png is an image that you generated ahead of time, to match when brushSize is 15, for example.
Btw P5.js is just setting the cursor CSS property. You can read more about it here.
If you want to go with the noCursor() approach and draw the ellipse yourself, you could draw your drawing to a buffer (the createGraphics() function is your friend) and then draw the ellipse on top of that every frame. I'd still probably use a cross cursor just because there's going to be some annoying lag if you draw it yourself.
Create a circular DIV inside the canvas container and show it on top of the actual canvas.
I have a series of dots with connected lines that I am animating in an easel.js canvas. The dots move around, and the lines stay connected to them as they move. As the dots move, I'm animating their color, so I want the lines to animate color as well.
I tried calling a color tween on the line, but it requires that I cache the line first.
For a circle, that's easy - I get the radius and, since its registration is in the center, its x and y coordinates and width and height are easy to calculate (for a circle with r=100 at 50,50, its cache would be cache(0,0,100,100). But for a line, I'm not sure how to reference the right coordinates for the cache statement, especially since the line start position, end position, and length are always changing.
Anyone have a way to do this?
I'm using greensock's timelinemax / tweenlite with the easeljs plugin to handle all the animations, if that's helpful.
If TweenLite handles color tweens, then you should just be able to update the "style" of your line any time:
var shape = new createjs.Shape();
var colorCommand = shape.graphics.beginStroke("#000000").command;
shape.graphics.moveTo(0,0).lineTo(100,100); // Draw the line
// Any time
colorCommand.style = "#ff0000";
// So in a tween:
TweenLite.to(colorCommand, 20, {style:"#00ffff"});
If you are using EaselJS, you can also use TweenJS, which has a ColorPlugin. Using similar code:
createjs.Tween.get(colorCommand).to({style:"#00fffff"}, 20000);
Here is a fiddle I made tweening the color of a line with TweenJS https://jsfiddle.net/lannymcnie/5zxpb944/
Cheers.
I need to clear a rectangle Drawn on Image in Canvas with out damage existing image. I can draw small rectangle points and clear that out. But the problem is when I clear rectangle it remains as white small patch on image.
Can someone tell me how to clear a rectangle on image without damage the existing image.
I have used following methods to clear rectangles but didn't work.
1) context.fillStyle ="white";
2) context.clearRect(xCoordinate, yCoordinate, 10, 08);
Thanks in advance!
Canvas doesn't work that way. It's a single layer, its also transparent by default. So with that in mind, you might be able to achieve what you want by simply giving the canvas element a CSS background. That way anything you draw on top of that background can easily be removed and the background will show through.
#backed-canvas{
background-image: url(http://www.placebear.com/300/200);
}
JSFiddle example: https://jsfiddle.net/yLf5erut/
There is one thing you can do.
When create a rectangle on the canvas just get the image data like:
var imgData = context.getImageData(xCoordinate, yCoordinate, 10, 8);
and draw the rectangle.
When clearing out the rectangle just place then image data back like this:
context.putImageData(imgData, xCoordinate, yCoordinate);
I suggest using 2 canvas elements one over another.
So you can have the original image drawn on the bottom canvas with low zIndex, and the top one with highter zIndex can be used to draw / clear whatever needed. This is a common practice, and for more complecated animations you will end up with better performance.
I have two canvases. I have made them circular using border-radius. The 2nd is positioned inside the first one (using absolute position).
I have click events on both circles. If you click on inside canvas, the color at the point of the click is loaded in the outside canvas with opacity varying from white to the picked color and finally to black. If you click on outer canvas the exact color value at that point is loaded in the text-box at the bottom
I am unable to click in red zones (as shown in figure below) of the outer canvas when using chrome. I tried z-idex, arcs but nothing is helping me. But In Firefox everything is working fine.
Note: You can drag the picker object in the outer circle. But if you leave it in red zones, you would not be able to click it again in Chrome. Clicking in green zone will get you its control again
Code in this JSFiddle
Edit
I excluded all irrelevant code to make it easy. Now there is only a container having two canvas.
Filled simply with two distinct colors. Open following fiddle link in both chrome and firefox. Click on both cirles in different zones and see difference in chrome and firefox. I want them to behave in chrome as they do in firefox
Note I will ultimately draw an image in inner canvas.
Updated Fiddle Link
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Your problem is because canvases currently are always rectangular, even if they don't look rectangular. Border radius makes the edges except the circle transparent, but it still doesn't stop events in Chrome on the corner areas. This is why you cannot click the bottom circle in those areas
I even tried putting it inside of a container that had a border-radius instead but the click event still goes through
With that being said, you have two options. You could either change your code to only use one canvas with the same type of layout, just drawing the background circle before the other each time. Essentially you'd draw a circle, draw your black to color to white gradient, use the xor operation to combine the two into one circle, then do the same with the rainbox gradient. You must draw the background circle first because canvas paints over the old layers every time
or
You could use javascript to only detect clicks in the circular area which takes just a little bit of math (: This solution is featured in edit below
In the future, CSS Shapes may allow canvases to be non-rectangular elements to be used, I'm actually not sure, but we don't have that capability yet at least
Edit
Alright, so after going through your code a bit it seems there are some things I should cover before I offer a solution
Setup all your finite variables outside of the functions that run every time. This means you don't put them (like radiuses, offsets, etc.) in the click function or something that runs often since they don't change
Your "radius"es are actually "diameter"s. The format of .rect goes .rect(x, y, width (diameter of circle), height (diameter of circle))
Almost always when overlaying canvases like you are you want to make them equal dimensions and starting position to prevent calculation error. In the end it makes it easier, doing all relative positioning with javascript instead of mixing it with CSS. In this case, however, since you're using border-radius instead of arc to make a circle, keep it like it is but position it using javascript ....
jQuery isn't needed for something this simple. If you're worried about any load speed I'd recommend doing it in vanilla javascript, essentially just changing the .click() functions into .onclick functions, but I left jQuery for now
You can declare multiple variables in a row without declaring var each time by using the following format:
var name1 = value1,
name2 = value2;
Variables with the same value you can declare like so:
var name1 = name2 = sameValue;
When children have position:absolute and you want it to be positioned relative to the parent, the parent can have position:relative, position:fixed, or position:absolute. I would think you'd want position:relative in this case
When you don't declare var for a variable it becomes global (unlessed chained with a comma like above). For more on that read this question
Now, onto the solution.
After talking with a friend I realized I could sort do the math calculation a lot easier than I originally thought. We can just calculate the center of the circles and use their radiuses and some if statements to make sure the clicks are in the bounds.
Here's the demo
After everything is set up correctly, you can use the following to detect whether or not it's in the bounds of each
function clickHandler(e, r) {
var ex = e.pageX,
ey = e.pageY,
// Distance from click to center
l = Math.sqrt(Math.pow(cx - ex, 2) + Math.pow(cy - ey, 2));
if(l > r) { // If the distance is greater than the radius
if(r === LARGE_RADIUS) { // Outside of the large
// Do nothing
} else { // The corner area you were having a problem with
clickHandler(e, LARGE_RADIUS);
}
} else {
if(r === LARGE_RADIUS) { // Inside the large cirle
alert('Outer canvas clicked x:' + ex + ',y:' + ey);
} else { // Inside the small circle
alert('Inner canvas clicked x:' + ex + ',y:' + ey);
}
}
}
// Just call the function with the appropriate radius on click
$(img_canvas).click(function(e) { clickHandler(e, SMALL_RADIUS); });
$(wheel_canvas).click(function(e) { clickHandler(e, LARGE_RADIUS); });
Hopefully the comments above and code make enough sense, I tried to clean it up as best as I could. If you have any questions don't hesitate to ask!
I have problem with canvas createPattern. I have two boxes, both will move after pressing a keyarrow:
Example:
http://jsfiddle.net/wA73R/1/
The problem is that the box background filled by createPattern also is moving. How to avoid that? Is there any solution? The big box is only an example (drawImage is not the good solution for me, I need something that will repeat background image).
Thank you for help
The problem is that the box background filled by createPattern also is moving.
Actually your problem is that the background is not moving - it is static, while you are drawing your rectangle to different positions.
How to avoid that?
The pattern will always be drawn at the coordinate origin, whose actual position is defined by the current transformation. In future you will be able to transform the pattern itself with the setTransform method, but since that currently is not implemented anywhere you instead will have to change the global transformation matrix.
In your case it means, that instead of drawing your rectangle at x/y, you translate the whole context to x/y and draw your rectangle at 0/0 then:
ctx.fillStyle=pattern;
ctx.save();
ctx.translate(boxes[i].x - left , boxes[i].y);
ctx.fillRect(0, 0, boxes[i].width, boxes[i].height);
ctx.restore();
(updated demo)