Is there a way to display or conceal a portion of a canvas image similar to how Image Sprite works?
For example:
Imagine you have a canvas with dimensions of 200x200.
When a specific button is clicked, I would like to reveal a section of the canvas from coordinates (100, 100) to (120, 120). On another button click, I want to display the entire canvas instead.
Can anyone provide guidance on how to achieve this effect?
To resolve the issue with sprites displayed as backgrounds within another element, one potential solution could be to hide the parent element altogether.
<style>
#sprite-container {
width: 100px;
height: 100px;
background-image: url(sprite.png);
background-position: 100px 100px;
}
</style>
<script>
var hidden = false;
function toggleVisibility() {
if(!hidden) {
document.getElementById("sprite-container").style.display="none";
hidden = true;
}
else {
document.getElementById("sprite-container").style.display="block";
hidden = false;
}
}
</script>
<div id="toggle-button" onclick="toggleVisibility();">Toggle Button</div>
<div id="sprite-container"></div>
If the sprite's original position is 100px from the left edge, an alternative approach can also involve using
document.getElementById('#sprite-container').style.backgroundPosition="200px 200px";To display a specific portion of an image, you can utilize the clipping form of drawImage:
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var cw=canvas.width;
var ch=canvas.height;
var img=new Image();
img.onload=start;
img.src="https://example.com/image.jpg";
function start(){
ctx.drawImage(img, 0,0,120,150, 0,0,120,150);
document.getElementById('partial').onclick=function(){
ctx.clearRect(0,0,cw,ch);
ctx.drawImage(img, 0,0,120,150, 0,0,120,150);
}
document.getElementById('full').onclick=function(){
ctx.clearRect(0,0,cw,ch);
ctx.drawImage(img, 0,0);
}
}body{ background-color: lightblue; }
#canvas{border:1px solid black;}<button id='partial'>Show partial canvas</button>
<button id='full'>Show full canvas</button>
<br><canvas id="canvas" width=400 height=400></canvas>You can use this technique to clip the image.
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
var btn = document.getElementById('btn');
var c = 0;
var img = new Image();
img.src = 'http://placehold.it/200/200';
img.onload = function() {
canvas.width = img.width;
canvas.height = img.height;
context.drawImage(img, 0, 0)
}
btn.onclick = function() {
if (c++ % 2 == 0) {
context.clearRect(0, 0, canvas.width, canvas.height);
context.drawImage(img, 100, 100, 20, 20, 100, 100, 20, 20);
btn.value = 'Unclip';
}
else {
context.drawImage(img, 0, 0);
btn.value = 'Clip';
}
}<input id="btn" type="button" value="Clip" /><br />
<canvas id="canvas"></canvas>If a user interacts with the canvas, you have the ability to capture the precise coordinates where the action occurred. By determining if these coordinates fall within a specific range, such as inside a circle, you can dynamically manipulate the image using clipping techniques.
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
var c = 0;
var img = new Image();
img.src = 'http://s25.postimg.org/cv29exevj/index.png';
img.onload = function() {
canvas.width = img.width;
canvas.height = img.height;
context.drawImage(img, 80, 80, 40, 40, 80, 80, 40, 40);
}
canvas.onclick = function(e) {
var x = e.clientX - canvas.getBoundingClientRect().left;
var y = e.clientY - canvas.getBoundingClientRect().top;
if (x >= 80 && x <= 120 && y >= 80 && y <= 120) {
if (c++ % 2 == 0) {
context.clearRect(0, 0, canvas.width, canvas.height);
context.drawImage(img, 0, 0);
} else {
context.clearRect(0, 0, canvas.width, canvas.height);
context.drawImage(img, 80, 80, 40, 40, 80, 80, 40, 40);
}
}
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