Javascript,css:将变换原点更改为gesturechange的centerpoint [英] Javascript, css: change transform origin to centerpoint of gesturechange
问题描述
我想将转换原点更改为缩放手势的中心点。
I would like to change the transform origin to the center point of the pinch gesture.
这个工作代码(safariDevSample)适用于缩放和旋转, c $ c> transform-origin :
This working code (safariDevSample) applies scale and rotation without changing the transform-origin
:
window.angle = 0; //global to store data for later reset ....
var newAngle;
window.scale = 1;
var newScale;
function saveChanges() {
window.angle = newAngle;
window.scale = newScale;
}
function getAngleAndScale(e) {
// Don't zoom or rotate the whole screen
e.preventDefault();
newAngle = window.angle + e.rotation;
newScale = window.scale * e.scale;
if (newScale < 1) newScale = 1; //prepend to scale smaller then parent
// Combine scale and rotation into a single transform
var tString = "rotate(" + newAngle + "deg) scale(" + newScale + ")";
document.getElementById("theImg").style.webkitTransform = tString;
}
function init() {
document.getElementById("theImg").addEventListener("gesturechange", getAngleAndScale, false);
document.getElementById("theImg").addEventListener("gestureend", saveChanges, false);
}
init();
我尝试使用 touchstart
gesturestart screenX screenY
作为附加事件监听器,但未成功。
I've tried to use touchstart
and gesturestart screenX screenY
as additional event listeners but without success.
推荐答案
猜我通过使用touchstart事件找到了一个工作解决方案。
首先得到一个修复过渡原点,然后将其转换为相对的。
这可以通过每个pinch ...
Guess I found a working solution by using the touchstart event. First get a fix transition origin and then convert it to a relative one. This can then be used thru the each pinch ...
var yO = 50;
var xO = 50;
window.scale = 1;
var newScale;
function saveChanges() {
window.scale = newScale;
}
function getTouchStartXY(e){
myTouchStartNullX = e.touches[0].pageX;
myTouchStartNullY = e.touches[0].pageY;
myTouchStartSecondX = e.touches[1].pageX;
myTouchStartSecondY = e.touches[1].pageY;
myTouchStartX = (myTouchStartNullX + myTouchStartSecondX)/2;
myTouchStartY = (myTouchStartNullY + myTouchStartSecondY)/2;
var boundingBox = document.getElementById('theImg').getBoundingClientRect();
picX = boundingBox.left;
picY = boundingBox.top;
picRight = boundingBox.right;
picBottom = boundingBox.bottom;
if(picX < 0 )picX = picX* (-1);
if(picY < 0 )picY = picY* (-1);
xO = ((picX + myTouchStartX)/(picX + picRight))*100;
yO = ((picY + myTouchStartY)/(picY + picBottom))*100;
document.getElementById("theImg").style['webkitTransformOrigin'] = xO + '% ' + yO + '%';
}
function getAngleAndScale(e) {
// Don't zoom or rotate the whole screen
e.preventDefault();
newScale = window.scale * e.scale;
//if(newScale < 1)newScale = 1;
// Combine scale and rotation into a single transform
var tString = "scale(" + newScale + ")";
document.getElementById("theImg").style['webkitTransform'] = tString;
}
function init() {
document.getElementById("theImg").addEventListener("touchstart", getTouchStartXY, false);
document.getElementById("theImg").addEventListener("gesturechange", getAngleAndScale, false);
document.getElementById("theImg").addEventListener("gestureend", saveChanges, false);
}
init();
Thx
Hans
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