How to set the image in the DIV to be vertically centered in CSS_html/css_WEB-ITnose

The use of DIV for positioning is now more and more widely used.
When I was using DIV to position pictures recently, I found that DIV cannot directly set the vertical alignment of the picture.
I was really troubled for a while, and then I found many solutions on the Internet.
But it didn’t seem to work, and then I discovered Mencius Chapter E (I was super surprised at the breadth of knowledge in Mencius Chapter E)
In a post to answer other people’s questions
there is a solution that looks very authentic. As follows

style ="position:absolute;
width:500px;
height:305px;
z-index:1 ;
background-color: #999999;
border: 1px none #000000;
padding-top:expression(this.style.top (this.offsetHeight-mxh.offsetHeight)/2)"
align =center >

div >

After using it, I found that it still failed.
Then I checked the information and found that there are two problems in his method.

What this.style.top takes out is not a number but a string, such as 50px, so there is no way to operate in expression. The correct method should be the this.style.pixelTop property, so that the numbers are taken out. After the picture is placed in a DIV, the calculation of its top attribute value no longer starts from the upper left corner of the window, but from the upper left corner of the DIV container. Therefore, the top padding distance of the DIV does not need to be added to the top value of the DIV.

Based on the above two points, I made slight modifications to the method in Chapter E of Mencius and got the following method. I've tested it successfully.
The whole process took a lot of time, so I will post it here to share with everyone, so as to save everyone from making further detours, especially those who have not used expression yet.

style ="
position:absolute;
left:261px;
top:50px;
wid th:251px;
Height:105px;
z-index:1;
overflow:hidden;
border: 1px solid #0066CC; expression
padding-top:((this.offsetHeight-myI mage.offsetHeight)/ 2);
" "
align ="center" >

div >

There is a key point to remind everyone that the picture must be given an ID before it can be calculated. Remember~

Thank you Mencius Chapter E for his erudition, hehehe
I am once again amazed by the breadth of knowledge in Mencius Chapter E.