Page Flip Effect In Pure Javascript

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 i

Solution 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 bookvarBOOK_WIDTH=630;
varBOOK_HEIGHT=260;

// Dimensions of one page in the bookvarPAGE_WIDTH=300;
varPAGE_HEIGHT=250;

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

// The canvas size equals to the book dimensions + this paddingvarCANVAS_PADDING=30;

varprogress=1;
vartarget= -1;

varcanvas= document.getElementById("pageflip-canvas");
varcontext= canvas.getContext("2d");
varfillElt= document.getElementById("fill");
vardroppedShadowElt= document.getElementById("droppedShadow");
varsharpShadowElt= document.getElementById("sharpShadow");
varprogressElt= document.getElementById("progress");
varfoldWidthElt= document.getElementById("foldWidth");
varfoldXElt= 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 bookvarstrength=1 - Math.abs(progress);

    // Width of the folded papervarfoldWidth= (PAGE_WIDTH * 0.5) * (1 - progress);

    // X position of the folded papervarfoldX= PAGE_WIDTH * progress + foldWidth;

    // How far the page should outdent vertically due to perspectivevarverticalOutdent=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)varpaperShadowWidth= (PAGE_WIDTH * 0.5) * Math.max(Math.min(1 - progress, 0.5), 0);
        varfoldGradient= 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 shadowvarrightShadowWidth= (PAGE_WIDTH * 0.5) * Math.max(Math.min(strength, 0.5), 0);
    varrightShadowGradient= 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 shadowvarleftShadowWidth= (PAGE_WIDTH * 0.5) * Math.max(Math.min(strength, 0.5), 0);
    varleftShadowGradient= 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.

Solution 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.