纯Javascript中的页面翻转效果 [英] Page Flip effect in pure Javascript

问题描述

对于电子书阅读器网络应用程序，我试图为电子书制作一个类似于花哨的书籍查看器，例如iBooks for iPad和iPhone。

For an ebook-reader webapp, im trying to make a fancy book-like viewer for the ebooks, like iBooks for iPad and iPhone.

我发现它非常好jQuery插件正是我试图达到的目标。唯一的问题是，它是一个jQuery插件，所以我不能使用它。怎么可能在纯Javascript中完成？

I found that excellent jQuery Plugin which is exactly what im trying to reach. The only problem is, its a jQuery Plugin, so i cant use that. How could something like that'be done in pure Javascript?

链接到jQuery页面翻转插件：转换JS jQuery插件

Link to the jQuery page flip plugin: Turn JS jQuery Plugin

推荐答案

尽管你可能认为单独使用JavaScript会更好，你应该明白这可能是非常困难的，如果没有正确的数学理解，所有这些都可能会花费你更多的时间来弄清楚你上面所示的插件。在Google的任何情况下，我都找到了一些可以让你朝着正确方向前进的jsfiddles。

As much as you might think this is better to do with JavaScript alone, you should understand that it's might be very difficult and without the proper math understanding and all it's probably going to take you more time to figure out then the plug in you have shown above. In any case with Google I have found a couple jsfiddles that can possible get you in the right direction.

纯JavaScript翻转效果： http://jsfiddle.net/maitrekaio/nuUNd/

Pure JavaScript flip effect: http://jsfiddle.net/maitrekaio/nuUNd/

// Dimensions of the whole book
var BOOK_WIDTH = 630;
var BOOK_HEIGHT = 260;

// Dimensions of one page in the book
var PAGE_WIDTH = 300;
var PAGE_HEIGHT = 250;

// Vertical spacing between the top edge of the book and the papers
var PAGE_Y = (BOOK_HEIGHT - PAGE_HEIGHT) / 2;

// The canvas size equals to the book dimensions + this padding
var CANVAS_PADDING = 30;

var progress = 1;
var target = -1;

var canvas = document.getElementById("pageflip-canvas");
var context = canvas.getContext("2d");
var fillElt = document.getElementById("fill");
var droppedShadowElt = document.getElementById("droppedShadow");
var sharpShadowElt = document.getElementById("sharpShadow");
var progressElt = document.getElementById("progress");
var foldWidthElt = document.getElementById("foldWidth");
var foldXElt = document.getElementById("foldX");

// Resize the canvas to match the book size
canvas.width = BOOK_WIDTH;
canvas.height = BOOK_HEIGHT + (CANVAS_PADDING * 2);

progressElt.addEventListener("change", render, false);

function render() {

    // Reset all pixels in the canvas
    context.clearRect(0, 0, canvas.width, canvas.height);

    // Ease progress towards the target value 
    progress = progressElt.value;
    // Strength of the fold is strongest in the middle of the book
    var strength = 1 - Math.abs(progress);

    // Width of the folded paper
    var foldWidth = (PAGE_WIDTH * 0.5) * (1 - progress);

    // X position of the folded paper
    var foldX = PAGE_WIDTH * progress + foldWidth;

    // How far the page should outdent vertically due to perspective
    var verticalOutdent = 20 * strength;

    foldWidthElt.value = foldWidth;
    foldXElt.value = foldX;

    context.save();
    context.translate((BOOK_WIDTH / 2), PAGE_Y + CANVAS_PADDING);

    drawFoldedPaper(foldX, foldWidth, verticalOutdent, fillElt.checked);


    if (sharpShadowElt.checked) {
        drawSharpShadow(foldX, foldWidth, verticalOutdent, strength);
    }

    if (droppedShadowElt.checked) {
        drawDroppedShadow(foldX, foldWidth, strength);
    }

    context.restore();
}


// Draw the folded piece of paper
function drawFoldedPaper(foldX, foldWidth, verticalOutdent, fill) {
    context.beginPath();
    context.moveTo(foldX, 0);
    context.lineTo(foldX, PAGE_HEIGHT);
    context.quadraticCurveTo(foldX, PAGE_HEIGHT + (verticalOutdent * 2), foldX - foldWidth, PAGE_HEIGHT + verticalOutdent);
    context.lineTo(foldX - foldWidth, -verticalOutdent);
    context.quadraticCurveTo(foldX, -verticalOutdent * 2, foldX, 0);

    if (fill) {
        // Gradient applied to the folded paper (highlights & shadows)
        var paperShadowWidth = (PAGE_WIDTH * 0.5) * Math.max(Math.min(1 - progress, 0.5), 0);
        var foldGradient = context.createLinearGradient(foldX - paperShadowWidth, 0, foldX, 0);
        foldGradient.addColorStop(0.35, '#fafafa');
        foldGradient.addColorStop(0.73, '#eeeeee');
        foldGradient.addColorStop(0.9, '#fafafa');
        foldGradient.addColorStop(1.0, '#e2e2e2');
        context.fillStyle = foldGradient;
        context.fill();
    }
    context.strokeStyle = 'rgba(0,0,0,0.06)';
    context.lineWidth = 2;
    context.stroke();
}

// Draw a sharp shadow on the left side of the page
function drawSharpShadow(foldX, foldWidth, verticalOutdent, strength) {
    context.strokeStyle = 'rgba(0,0,0,'+(0.05 * strength)+')';
    context.lineWidth = 30 * strength;
    context.beginPath();
    context.moveTo(foldX - foldWidth, -verticalOutdent * 0.5);
    context.lineTo(foldX - foldWidth, PAGE_HEIGHT + (verticalOutdent * 0.5));
    context.stroke();
}

function drawDroppedShadow(foldX, foldWidth, strength) {    
    // Right side drop shadow
    var rightShadowWidth = (PAGE_WIDTH * 0.5) * Math.max(Math.min(strength, 0.5), 0);
    var rightShadowGradient = context.createLinearGradient(foldX, 0, foldX + rightShadowWidth, 0);
    rightShadowGradient.addColorStop(0, 'rgba(0,0,0,'+(strength*0.2)+')');
    rightShadowGradient.addColorStop(0.8, 'rgba(0,0,0,0.0)');

    context.fillStyle = rightShadowGradient;
    context.beginPath();
    context.moveTo(foldX, 0);
    context.lineTo(foldX + rightShadowWidth, 0);
    context.lineTo(foldX + rightShadowWidth, PAGE_HEIGHT);
    context.lineTo(foldX, PAGE_HEIGHT);
    context.fill();


    // Left side drop shadow
    var leftShadowWidth = (PAGE_WIDTH * 0.5) * Math.max(Math.min(strength, 0.5), 0);
    var leftShadowGradient = context.createLinearGradient(foldX - foldWidth - leftShadowWidth, 0, foldX - foldWidth, 0);
    leftShadowGradient.addColorStop(0, 'rgba(0,0,0,0.0)');
    leftShadowGradient.addColorStop(1, 'rgba(0,0,0,'+(strength*0.15)+')');

    context.fillStyle = leftShadowGradient;
    context.beginPath();
    context.moveTo(foldX - foldWidth - leftShadowWidth, 0);
    context.lineTo(foldX - foldWidth, 0);
    context.lineTo(foldX - foldWidth, PAGE_HEIGHT);
    context.lineTo(foldX - foldWidth - leftShadowWidth, PAGE_HEIGHT);
    context.fill();    
}

jQuery翻转效果（这不应该是转换为纯JavaScript的问题） ： http://jsfiddle.net/pixelass/TW43V/61/

jQuery flip effect (that shouldn't be an issue converting to pure JavaScript): http://jsfiddle.net/pixelass/TW43V/61/

另一个jQuery翻转效果： http://jsfiddle.net/wdm954 / DkZsY / 2 /

Another jQuery flip effect: http://jsfiddle.net/wdm954/DkZsY/2/

因为你想要纯JavaScript知道你需要弄清楚如何自己做这件事。使用这些示例作为指导将有所帮助，即使它们不是纯粹的js。

because you want pure JavaScript know you'll need to figure out how to do this on your own. Using these examples as guidelines will be helpful even if they are not pure js.

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