我正在 html 5 Canvas 上开发一个游戏，我必须将图像剪辑成多种形状。我还想使用鼠标事件加入这些剪辑的图像。我可以只剪一个正方形吗？另外，是否有必要保存每个剪切图像的 x 和 y 坐标以了解其位置，或者是否有其他方法？
最佳答案
这里有一个示例来说明如何:
- 将图像剪裁成 4 个三 Angular 形 block ，
- 对片段进行 HitTest ，
- 使用鼠标移动棋子
这是代码和 fiddle :http://jsfiddle.net/m1erickson/r59ch/
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<style>
body{ background-color: ivory; }
#canvas{border:1px solid red;}
</style>
<script>
$(function(){
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var $canvas=$("#canvas");
var canvasOffset=$canvas.offset();
var offsetX=canvasOffset.left;
var offsetY=canvasOffset.top;
var scrollX=$canvas.scrollLeft();
var scrollY=$canvas.scrollTop();
var isDown=false;
var startX;
var startY;
var parts=[];
var selectedPart=-1;
var img=new Image();
img.onload=function(){
var cx=img.width/2;
var cy=img.height/2;
var w=img.width;
var h=img.height;
parts.push({x:25,y:25,points:[{x:0,y:0},{x:cx,y:cy},{x:0,y:h}]});
parts.push({x:25,y:25,points:[{x:0,y:0},{x:cx,y:cy},{x:w,y:0}]});
parts.push({x:125,y:25,points:[{x:w,y:0},{x:cx,y:cy},{x:w,y:h}]});
parts.push({x:25,y:25,points:[{x:0,y:h},{x:cx,y:cy},{x:w,y:h}]});
drawAll();
}
img.src="https://dl.dropboxusercontent.com/u/139992952/stackoverflow/house100x100.png";
function drawAll(){
ctx.clearRect(0,0,canvas.width,canvas.height);
for(var i=0;i<parts.length;i++){
draw(parts[i]);
}
}
function draw(part){
ctx.save();
define(part);
ctx.clip();
ctx.drawImage(img,part.x,part.y);
ctx.stroke();
ctx.restore();
}
function hit(part,x,y){
define(part);
return(ctx.isPointInPath(x,y))
}
function move(part,x,y){
part.x+=x;
part.y+=y;
draw(part);
}
function define(part){
ctx.save();
ctx.translate(part.x,part.y);
ctx.beginPath();
var point=part.points[0];
ctx.moveTo(point.x,point.y);
for(var i=0;i<part.points.length;i++){
var point=part.points[i];
ctx.lineTo(point.x,point.y);
}
ctx.closePath();
ctx.restore();
}
function handleMouseDown(e){
e.preventDefault();
startX=parseInt(e.clientX-offsetX);
startY=parseInt(e.clientY-offsetY);
// Put your mousedown stuff here
for(var i=0;i<parts.length;i++){
if(hit(parts[i],startX,startY)){
isDown=true;
selectedPart=i;
return;
}
}
selectedPart=-1;
}
function handleMouseUp(e){
e.preventDefault();
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
// Put your mouseup stuff here
isDown=false;
}
function handleMouseOut(e){
e.preventDefault();
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
// Put your mouseOut stuff here
isDown=false;
}
function handleMouseMove(e){
if(!isDown){return;}
e.preventDefault();
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
// Put your mousemove stuff here
var dx=mouseX-startX;
var dy=mouseY-startY;
startX=mouseX;
startY=mouseY;
//
var part=parts[selectedPart];
move(part,dx,dy);
drawAll();
}
$("#canvas").mousedown(function(e){handleMouseDown(e);});
$("#canvas").mousemove(function(e){handleMouseMove(e);});
$("#canvas").mouseup(function(e){handleMouseUp(e);});
$("#canvas").mouseout(function(e){handleMouseOut(e);});
}); // end $(function(){});
</script>
</head>
<body>
<h4>Drag the right triangle-image into place</h4>
<canvas id="canvas" width=300 height=300></canvas>
</body>
</html>
关于javascript - 在 html5 Canvas 中将图像剪切成不同的形状，如三 Angular 形、五边形？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/21299439/