scaling image on pinch gesture

Question

I'm using the jQuery touchy plugin for detecting the pinch event to give users the ability to zoom in/out on an image. Here's the gist of my code:

var w = 800,
    h = 600;
$('img').on('touchy-pinch', function (e, $target, data) {
    $(this).css({
        width: w * data.scale,
        height: h * data.scale
    });
});

Where the custom data object contains the following:

• scale
• previousScale
• currentPoint
• startPoint
• startDistance

It works fine on the first pinch, but once my fingers leave the screen and then I try to do it again, the image re-scales back up. How can I modify my handler so that the image continues where it left off rather than re-scale? Using the data's previousScale didn't help since the previousScale just gets reset as well.

Collyrium

Answer 1

The problem here is that you're not resetting your vars w and h to their post-scaled values, only the css, so the style reverts back to 800x600 on another scale event. You need a persistent w and h that are set to w*data.scale and h*data.scale on the scale event.

Exercise