Pinch to zoom using Hammer.js

Question

I am trying to implement pinch to zoom using hammer.js

Here\'s my HTML-

Answer 1

Add variables last_posX and last_posY to account for the change in position when you have translated. update them on dragend so that next time a drag event is captured it takes into account where the last drag ended

var posX=0, posY=0,
    scale=1, last_scale,
    last_posX=0, last_posY=0,
    max_pos_x=0, max_pos_y=0;

hammertime.on('touch drag transform dragend', function(ev) {
    switch(ev.type) {
        case 'touch':
            last_scale = scale;
            break;

        case 'drag':
            if(scale != 1){
                    posX = last_posX + ev.gesture.deltaX;
                    posY = last_posY + ev.gesture.deltaY;
                    if(posX > max_pos_x){
                        posX = max_pos_x;
                    }
                    if(posX < -max_pos_x){
                        posX = -max_pos_x;
                    }
                    if(posY > max_pos_y){
                        posY = max_pos_y;
                    }
                    if(posY < -max_pos_y){
                        posY = -max_pos_y;
                    }
            }else{
                posX = 0;
                posY = 0;
                saved_posX = 0;
                saved_posY = 0;
            }
            break;

        case 'transform':
            scale = Math.max(1, Math.min(last_scale * ev.gesture.scale, 10));
            max_pos_x = Math.ceil((scale - 1) * rect.clientWidth / 2);
            max_pos_y = Math.ceil((scale - 1) * rect.clientHeight / 2);
            if(posX > max_pos_x){
                posX = max_pos_x;
            }
            if(posX < -max_pos_x){
                posX = -max_pos_x;
            }
            if(posY > max_pos_y){
                posY = max_pos_y;
            }
            if(posY < -max_pos_y){
                posY = -max_pos_y;
            }
            break;
        case 'dragend':
            last_posX = posX < max_pos_x ? posX: max_pos_x;
            last_posY = posY < max_pos_y ? posY: max_pos_y;
            break;
    }

    // transform!
    var transform =
            "translate3d(0, 0, 0) " +
            "scale3d(1, 1, 0) "; 
    if(scale != 1){
        transform =
            "translate3d("+posX+"px,"+posY+"px, 0) " +
            "scale3d("+scale+","+scale+", 0) ";
    }

    rect.style.transform = transform;
    rect.style.oTransform = transform;
    rect.style.msTransform = transform;
    rect.style.mozTransform = transform;
    rect.style.webkitTransform = transform;
});