问题
For an ebook-reader webapp, im trying to make a fancy book-like viewer for the ebooks, like iBooks for iPad and iPhone.
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?
Link to the jQuery page flip plugin: Turn JS jQuery Plugin
回答1:
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.
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 flip effect (that shouldn't be an issue converting to pure JavaScript): http://jsfiddle.net/pixelass/TW43V/61/
Another jQuery flip effect: http://jsfiddle.net/wdm954/DkZsY/2/
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.
回答2:
This question is rather old but I'll place a reference where idea for approved answer has been taken from - http://www.html5rocks.com/en/tutorials/casestudies/20things_pageflip/. Good tutorial with explanation and examples.
来源：https://stackoverflow.com/questions/15904594/page-flip-effect-in-pure-javascript