Échantillon de zoom dans la toile
<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="" height=""
style="border:1px solid #d3d3d3;">
Your browser does not support the canvas element.
</canvas>
<script>
console.log("canvas")
var ox=0,oy=0,px=0,py=0,scx=1,scy=1;
var canvas = document.getElementById("myCanvas");
canvas.onmousedown=(e)=>{px=e.x;py=e.y;canvas.onmousemove=(e)=>{ox-=(e.x-px);oy-=(e.y-py);px=e.x;py=e.y;} }
canvas.onmouseup=()=>{canvas.onmousemove=null;}
canvas.onwheel =(e)=>{let bfzx,bfzy,afzx,afzy;[bfzx,bfzy]=StoW(e.x,e.y);scx-=10*scx/e.deltaY;scy-=10*scy/e.deltaY;
[afzx,afzy]=StoW(e.x,e.y);
ox+=(bfzx-afzx);
oy+=(bfzy-afzy);
}
var ctx = canvas.getContext("2d");
function draw(){
window.requestAnimationFrame(draw);
ctx.clearRect(0,0,canvas.width,canvas.height);
for(let i=0;i<=100;i+=10){
let sx=0,sy=i;
let ex=100,ey=i;
[sx,sy]=WtoS(sx,sy);
[ex,ey]=WtoS(ex,ey);
ctx.beginPath();
ctx.moveTo(sx, sy);
ctx.lineTo(ex, ey);
ctx.stroke();
}
for(let i=0;i<=100;i+=10){
let sx=i,sy=0;
let ex=i,ey=100;
[sx,sy]=WtoS(sx,sy);
[ex,ey]=WtoS(ex,ey);
ctx.beginPath();
ctx.moveTo(sx, sy);
ctx.lineTo(ex, ey);
ctx.stroke();
}
}
draw()
function WtoS(wx,wy){
let sx=(wx-ox)*scx;
let sy=(wy-oy)*scy;
return[sx,sy];
}
function StoW(sx,sy){
let wx=sx/scx+ox;
let wy=sy/scy+oy;
return[wx,wy];
}
</script>
</body>
</html>
elcharitas