I am learning drawing canvas and now I have task. I need to add an image within the inner circle. The image position needs to be inside the circle. Also I attached the image with this post. My code are:
<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="200" height="100" style="border:1px solid #c3c3c3;">
Your browser does not support the HTML5 canvas tag.
</canvas>
<script>
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.fillStyle = "green";
ctx.fillRect(0,0,200,100);
var cicleT = document.getElementById("myCanvas");
var dtx = cicleT.getContext("2d");
dtx.arc(95,50,40,0,2*Math.PI);
dtx.stroke();
dtx.fillStyle = "red";
dtx.fill();
dtx.fillStyle = "black"; // font color to write the text with
var font = "bold 13px serif";
dtx.font = font;
dtx.textBaseline = "bottom";
dtx.fillText("Bangladesh",50,50, 95 ,25);
</script>
</body>
</html>
You can use ctx.clip to cut out the region you want to draw, and the following operation will be refined on the region, remember to restore when you complete the works that needs to be refined.
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.fillStyle = "green";
ctx.fillRect(0, 0, 200, 100);
ctx.arc(95,50,40,0,2*Math.PI);
ctx.stroke();
ctx.fillStyle = "red";
ctx.fill();
// For safety, I move the draw image and draw text to image.onload.
var image = document.createElement('img');
image.onload = function() {
var iw = image.width;
var ih = image.height;
var r = Math.sqrt(Math.pow(iw/2, 2) + Math.pow(ih/2, 2));
var ratio = 40 / r;
var tw = iw * ratio;
var th = ih * ratio;
// Use the same ctx is ok.
ctx.arc(95, 50, 40, 0, 2 * Math.PI);
ctx.stroke();
// Save the current state of context, which is not clipped yet.
ctx.save();
// Clip by the stroke.
ctx.clip();
// Draw image.
//
ctx.drawImage(image, 0, 0, iw, ih, 95 - tw/2, 50 - th/2, tw, th);
// Restore the context, otherwise the text will also be clipped.
ctx.restore();
ctx.fillStyle = "black"; // font color to write the text with
var font = "bold 13px serif";
ctx.font = font;
ctx.textBaseline = "bottom";
ctx.fillText("Bangladesh", 50, 50, 95, 25);
};
image.src = "https://i.stack.imgur.com/jy3YL.jpg";
<canvas id="myCanvas" width="200" height="100" style="border:1px solid #c3c3c3;">
Your browser does not support the HTML5 canvas tag.
</canvas>
Related
I want to remove the intersection of two shapes, I understand that to do this I can use the XOR operation. the problem is that I need these two shapes to be transparent. By making the two shapes transparent the intersection is not eliminated.
<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="300" height="150" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.</canvas>
<script>
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.fillStyle = "red";
ctx.fillRect(20, 20, 75, 50);
ctx.fillStyle = "blue";
ctx.globalCompositeOperation = "xor";
ctx.fillRect(50, 50, 75, 50);
ctx.fillStyle = "rgba(255,0,0,0.5)";
ctx.fillRect(150, 20, 75, 50);
ctx.fillStyle = "rgba(40,23,0,0.5)";
ctx.globalCompositeOperation = "xor";
ctx.fillRect(180, 50, 75, 50);
</script>
</body>
</html>
Note: In the real problem it is not possible for me to generate an image, as proposed here
A simple (possibly simplistic, but it works) way of clearing pixels in overlapping images is to draw each image on its own canvas as well as on the main canvas.
We can then go through the main canvas pixel by pixel clearing any pixel which is in both images, even if it has only very slight opacity.
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.fillStyle = "rgba(255,0,0,0.5)";
ctx.fillRect(150, 20, 75, 50);
ctx.fillStyle = "rgba(40,23,0,0.5)";
ctx.globalCompositeOperation = "xor";
ctx.fillRect(180, 50, 75, 50);
var c1 = document.createElement('canvas');
var ctx1 = c1.getContext("2d");
ctx1.fillStyle = "rgba(255,0,0,0.5)";
ctx1.fillRect(150, 20, 75, 50);
var c2 = document.createElement('canvas');
var ctx2 = c2.getContext("2d");
ctx2.fillStyle = "rgba(40,23,0,0.5)";
ctx2.fillRect(180, 50, 75, 50);
let imgData = ctx.getImageData(0, 0, 300, 150);
for (let i=0; i < 300; i++) {
for (let j = 0; j < 150; j++) {
//clear the pixel if both images have opacity>0 there
if (ctx1.getImageData(i, j, 1, 1).data[3] && ctx2.getImageData(i, j, 1, 1).data[3] ) {
ctx.clearRect(i, j, 1, 1);
}
}
}
<canvas id="myCanvas" width="300" height="150" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.</canvas>
I want to retrieve the corresponding points to a 'outlinestroke' and save it as a Shape, instead of a "path with a stroke"
<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="300" height="150" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.</canvas>
<script>
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.beginPath();
ctx.moveTo(20, 20);
ctx.lineWidth = 12;
ctx.lineCap = 'round'
ctx.quadraticCurveTo(20, 100, 200, 20);
ctx.stroke();
</script>
</body>
</html>
This is the result of the code:
But I want to have the Outline of this stroke, and turn it into a Path and give it a stroke.
The fill should be transparent.
And only have a small outline.
Is there a way to "trace or convert" the stroke to a outline path to get the following result:
And if this is not possible:
Before drawing, to use the given points to define the shape of a path.
Here is what I tried:
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
var width = 12;
ctx.beginPath();
ctx.moveTo(20, 20);
ctx.lineWidth = width;
ctx.quadraticCurveTo(20, 100, 200, 20);
ctx.stroke();
ctx.beginPath();
ctx.lineWidth = 1;
ctx.fillStyle = "#ccc";
ctx.moveTo(20-width/2, 270);
ctx.quadraticCurveTo(20-width/2, 350+width/2, 200-width/2, 270+width/2);
ctx.lineTo(200-width/2, 270-width/2);
ctx.quadraticCurveTo(20+width/2, 350-width/2, 20+width/2, 270-width/2);
ctx.lineTo(20-width/2, 270);
ctx.fillStyle = "#999";
ctx.fill();
ctx.stroke();
ctx.closePath();
Which results in the following:
There are no API features to turn a strokes outline into a path.
You can however use a composite operation to create the inner transparency.
Example
Creating outline using globalCompositeOperation = "destination-out";
The gradient is just to show it is transparent.
const OUTLINE_WIDTH = 1; // in pixels
var ctx = canvas.getContext("2d");
ctx.lineWidth = 22;
ctx.lineCap = 'round'
ctx.beginPath();
ctx.moveTo(20, 20);
ctx.quadraticCurveTo(20, 100, 200, 20);
ctx.stroke();
ctx.globalCompositeOperation = "destination-out";
ctx.lineWidth = 22 - OUTLINE_WIDTH * 2;
ctx.stroke();
ctx.globalCompositeOperation = "source-over"; // restore default
canvas {
border:1px solid #aaa;
background: linear-gradient(90deg, rgba(180,255,224,1) 0%, rgba(169,169,255,1) 100%);
}
<canvas id="canvas"></canvas>
I am trying to write the description of each edge along the rectangle. The reason is to describe the length of each edge inside and outside rectangles (alongside). Is there a way I can achieve it?
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
// Clip a rectangular area
ctx.rect(50, 20, 200, 120);
ctx.stroke();
ctx.clip();
// Draw red rectangle after clip()
ctx.fillStyle = "red";
ctx.fillRect(0, 0, 150, 100);
This should show 200 above the top edge (outside) and 150 along the left edge (outside)
Using #stealththeninja's comment (pointing to this answer - text in html canvas) and this jsfiddle (for text rotation), I was able to build the code below. Hope it fits within your specs.
Screenshot of the result attached.
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
const rectPosX = 50;
const rectPosY = 50;
const rectLength = 200;
const rectHeight = 150;
ctx.fillStyle = "red";
ctx.fillRect(rectPosX, rectPosY, rectLength, rectHeight);
ctx.fillStyle = "blue";
ctx.fillText('200', rectPosX + rectLength / 2, rectPosY);
ctx.fillText('150', rectPosX, rectPosY + rectHeight / 2);
ctx.fillText('200', rectPosX + rectLength / 2, rectPosY + rectHeight);
ctx.save();
ctx.translate(rectPosX + rectLength, rectPosY + rectHeight / 2);
ctx.rotate(0.5*Math.PI);
ctx.fillText('150', 0, 0);
ctx.restore();
<canvas id="myCanvas" width="400" height="300"></canvas>
I am trying to create an HTML5 canvas which displays text and onmouseover will remove that text and display a different bit of text.
This works fine for changing the colour - essentially just creating a new canvas over the current one.
However, onmouseover the new text displays but the previous text remains.
http://jsfiddle.net/3j2b2egb/
HTML:
<body onload="changeBack()">
<canvas id="test"
width="330"
height="200"
style="border:1px solid #787878;"
onmouseover="change()"
onmouseout="changeBack()">
</canvas>
Javascript:
function changeBack() {
var c = document.getElementById("test");
var ctx = c.getContext("2d");
ctx.fillStyle = "blue";
ctx.font = "bold 16px Arial";
ctx.fillText("hello", 100, 100);
}
function change() {
var c = document.getElementById("test");
var ctx = c.getContext("2d");
ctx.fillStyle = "blue";
ctx.font = "bold 16px Arial";
ctx.fillText("world", 100, 100);
}
Try this. I have cleared canvas before drawing it.
function changeBack() {
var c = document.getElementById("test");
var ctx = c.getContext("2d");
ctx.clearRect ( 0 , 0 , c.width, c.height );
ctx.fillStyle = "blue";
ctx.font = "bold 16px Arial";
ctx.fillText("hello", 100, 100);
}
function change() {
var c = document.getElementById("test");
var ctx = c.getContext("2d");
ctx.clearRect ( 0 , 0 , c.width, c.height );
ctx.fillStyle = "red";
ctx.font = "bold 16px Arial";
ctx.fillText("world", 100, 100);
}
Here is working demo http://jsfiddle.net/3j2b2egb/1/
I am working in Jquery.
I have 4 Cordinates , Width, Height, x Position and Y position.
How can i create a Square shape Using This
$('#box').drawRect(20,20,2,30,{color:'red'})
I tried this and Not Working. Looking for a Good Hand
Here is My Demo. http://fiddle.jshell.net/vbm2vhu4/
try using canvas tag in JavaScript..
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.rect(20, 20, 150, 100);
ctx.stroke();
<canvas id="myCanvas" width="300" height="150" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.</canvas>
JSFIDDLE
JAVASCRIPT
Draw a circle
$(document).ready(function(){
var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');
var centerX = canvas.width / 2;
var centerY = canvas.height / 2;
var radius = 70;
context.beginPath();
context.arc(centerX, centerY, radius, 0, 2 * Math.PI, false);
context.fillStyle = 'green';
context.fill();
context.lineWidth = 5;
context.strokeStyle = '#003300';
context.stroke();
});
Drawing a rectangle requires canvas. You really do not need to use jquery for it. It can be well done with Javascript. I am attaching my example here.
<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="300" height="150">
Browser does not support the HTML5 canvas tag.</canvas>
<script>
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
// Blue rectangle
ctx.beginPath();
ctx.lineWidth = "10";
ctx.strokeStyle = "blue";
ctx.rect(50, 50, 50, 50);
ctx.stroke();
</script>
</body>
</html>
Paste this into a notepad and save as .html and load it in your browser
or jsfiddle http://jsfiddle.net/ssbiswal1987/vsbak0mq/