从matrix3d中获取CSS3旋转周期的数量

Question

我正在尝试使用CSS3 rotateY旋转图像。我需要使用jQuery获得旋转的角度。

我的问题是理解图像旋转了多少圈。

的例子:

180 degrees: matrix3d(-1, 0, -0.00000000000000012246467991473532, 0, 0, 1, 0, 0, 0.00000000000000012246467991473532, 0, -1, 0, 0, 0, 0, 1) 
360 degrees: matrix3d(1, 0, 0.00000000000000024492935982947064, 0, 0, 1, 0, 0, -0.00000000000000024492935982947064, 0, 1, 0, 0, 0, 0, 1)
540 degrees: matrix3d(-1, 0, -0.00000000000000036739403974420594, 0, 0, 1, 0, 0, 0.00000000000000036739403974420594, 0, -1, 0, 0, 0, 0, 1) 
720 degrees: matrix3d(1, 0, 0.0000000000000004898587196589413, 0, 0, 1, 0, 0, -0.0000000000000004898587196589413, 0, 1, 0, 0, 0, 0, 1)

可以看到，每180度，第三个元素的绝对值加0.00000000000000012246467991473532。我会对这个结果感到满意，然而在某些时候，这个逻辑打破了，不再适用了。

在第4个循环之后，被添加的数字变成随机的。

获得旋转周期数的正确方法是什么?

Answer 1

-------------------------- <</strong博士strong> TL;> --------------------------

function getRotationCycle (domElement, axis) {
    var computedStyle = window.getComputedStyle(domElement),
        matrixStyle = computedStyle.transform || computedStyle.WebkitTransform || computedStyle.MozTransform || computedStyle.msTransform || computedStyle.OTransform || computedStyle.KhtmlTransform;
    if (!matrixStyle || matrixStyle.substr(0, 9) !== 'matrix3d(') {
        //return 0; //????
        throw "Something's wrong with 3D transform style. Probably no style applied at all OR unknown CSS3 vendor OR unknown/unsupported 3D matrix representation string OR CSS3 3D transform is not fully supported in this browser";
    }
    var matrix = WebKitCSSMatrix && (new WebKitCSSMatrix(matrixStyle)) || 
                 MozCSSMatrix && (new MozCSSMatrix(matrixStyle)) || 
                 MsCSSMatrix && (new MsCSSMatrix(matrixStyle)) || 
                 OCSSMatrix && (new OCSSMatrix(matrixStyle)) ||     
                 CSSMatrix && (new CSSMatrix(matrixStyle)));
    if (!matrix || isNaN(matrix.a) || isNaN(matrix.b) || isNaN(matrix.c)) {
        //not sure about all versions of FireFox
        throw "Could not catch CSSMatrix constructor for current browser, OR the constructor has returned a non-standard matrix object (need [a b c] numerical properties to work)";
    }
    var rotation; 
    // todo: giving an axis array is a good idea, or we could return all three rotations if no parameter given
    switch (axis.toUpperCase()) {
        case 'X':
            rotation = Math.acos(matrix.a);
            break; 
        case 'Y':
            rotation = Math.asin(matrix.b);
            break; 
        case 'Z':
            throw "TODO: Sorry, Math people. I really need help here! Please implement this case for me. This will help you: http://9elements.com/html5demos/matrix3d/";
            //rotation = Math.acos(matrix.a);
            break;
        default:
            throw "This function accepts rotation axis name (string) as the first parameter. Possible values: 'X', 'Y', 'Z'"; 
    }
    //if (isNaN(rotation))...
    rotation *= 180/Math.PI; //getting rotation in degrees. This is good for me for debug purposes but bad for performance, of course, ...
    return rotation % 360; // ... so you can skip degrees and do it in radians only
}

更多的文档在这里:https://developer.mozilla.org，谷歌和微软似乎没什么有用的，苹果有一些。

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一切都从这篇文章开始:css3转换matrix3d值。感谢作者提供的起点和数学转换。

但是给出的答案不完整，它只在WebKit中工作。

工作代码是用纯JavaScript编写的，因为:-它可以复制粘贴到任何环境-它的工作速度快一点(或很多，取决于)

如果你想要jQuery版本，使用这个代码片段来获取matrixStyle字符串。

var matrixStyle = element$.css('transform')) || element$.css('-webkit-transform')) || element$.css('-moz-transform')) || element$.css('-ms-transform')) || element$.css('-o-transform')); // jQuery

矩阵的每一部分都在这里解释:http://9elements.com/html5demos/matrix3d/