让图片旋转任意角度及JQuery插件使用介绍

jQuery.fn.rotate = function(angle,whence) {

var p = this.get(0);

// 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.round(Math.cos(rotation) * 1000) / 1000;

var sintheta = Math.round(Math.sin(rotation) * 1000) / 1000;

//alert(costheta+","+sintheta);

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);

}

jQuery.fn.rotateRight = function(angle) {

this.rotate(angle==undefined?90:angle);

}

jQuery.fn.rotateLeft = function(angle) {

this.rotate(angle==undefined?-90:-angle);

}