讓圖片在div盒子中水平垂直居中

//調整多張圖片，讓圖片水平垂直居中

function adjustImg(){

let imgDiv = document.getElementsByClassName("img");//找到img標簽外面的class 名為img的div盒子

for (let i = 0; i < imgDiv.length; i++){

// console.log(i);

let obj = imgDiv[i].getElementsByTagName("img")[0];

if (obj.complete) {//確保圖片已經加載完成

let imgH = obj.offsetHeight;

let imgW = obj.offsetWidth;

let img_scale = imgW/imgH;

let boxH = obj.parentNode.offsetHeight;

let boxW = obj.parentNode.offsetWidth;

let box_scale = boxW / boxH;

// console.log("imgH="+imgH+" imgW="+imgW+" boxH="+boxH+" boxW="+boxW);

if(box_scale > img_scale){

obj.style.width = "100%";

imgH = obj.offsetHeight;

imgW = obj.offsetWidth;

let h = (imgH-boxH)/2;

obj.style.marginTop = -h + "px"; //確保圖片垂直居中

}else{

obj.style.height = "100%";

imgH = obj.offsetHeight;

imgW = obj.offsetWidth;

let w = (imgW-boxW)/2;

obj.style.marginLeft = -w + "px";

}

} else {

obj.onload = function(){

let imgH = obj.offsetHeight;

let imgW = obj.offsetWidth;

let img_scale = imgW/imgH;

let boxH = obj.parentNode.offsetHeight;

let boxW = obj.parentNode.offsetWidth;

let box_scale = boxW / boxH;

// console.log("imgH="+imgH+" imgW="+imgW+" boxH="+boxH+" boxW="+boxW);

if(box_scale > img_scale){

obj.style.width = "100%";

imgH = obj.offsetHeight;

imgW = obj.offsetWidth;

let h = (imgH-boxH)/2;

obj.style.marginTop = -h + "px";

}else{

obj.style.height = "100%";

imgH = obj.offsetHeight;

imgW = obj.offsetWidth;

let w = (imgW-boxW)/2;

obj.style.marginLeft = -w + "px";

}

};

// obj.style.height = "100%";

// obj.style.margin = "0 auto";

}

}

}