任意旋转图片的js实例

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Html代码

Js代码

function rotate(id,angle,whence){

var p=document.getElementById(id);

//we store the angle inside the image tag for persistence

if(!whence){

p.angle=((p.angle==undefined?0:p.angle)+angle)%360;

}else{

p.angle=angle;

}

if(p.angle>=0){

var rotation=Math.PI*p.angle/180;

}else{

var rotation=Math.PI*(360+p.angle)/180;

}

var costheta=Math.cos(rotation);

var sintheta=Math.sin(rotation);

if(document.all&&!window.opera){

var canvas=document.createElement('img');

canvas.src=p.src;

canvas.height=p.height;

canvas.width=p.width;

canvas.style.filter="progid:DXImageTransform.Microsoft.Matrix(M11="+costheta+",M12="+(-sintheta)+",M21="+sintheta+",M22="+costheta+",SizingMethod='auto expand')";

}else{

var canvas=document.createElement('canvas');

if(!p.oImage){

canvas.oImage=new Image();

canvas.oImage.src=p.src;

}else{

canvas.oImage=p.oImage;

}

canvas.style.width=canvas.width=Math.abs(costheta*canvas.oImage.width)+Math.abs(sintheta*canvas.oImage.height);

canvas.style.height=canvas.height=Math.abs(costheta*canvas.oImage.height)+Math.abs(sintheta*canvas.oImage.width);

var context=canvas.getContext('2d');

context.save();

if(rotation<=Math.PI/2){

context.translate(sintheta*canvas.oImage.height,0);

}else if(rotation<=Math.PI){

context.translate(canvas.width,-costheta*canvas.oImage.height);

}else if(rotation<=1.5*Math.PI){

context.translate(-costheta*canvas.oImage.width,canvas.height);

}else{

context.translate(0,-sintheta*canvas.oImage.width);

}

context.rotate(rotation);

context.drawImage(canvas.oImage,0,0,canvas.oImage.width,canvas.oImage.height);

context.restore();

}

canvas.id=p.id;

canvas.angle=p.angle;

p.parentNode.replaceChild(canvas,p);

}

function rotateRight(id,angle){

rotate(id,angle==undefined?90:angle);

}

function rotateLeft(id,angle){

rotate(id,angle==undefined?-90:-angle);

}

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