Z索引和相对位置

Question

I have a modal, that is show/hide using JavaScript.

In the modal an image will be inserted using JavaScript. Also over the image a div element will exist that will simulate cropping (get the coordinates of the image).

I have a problem making the image to stay below the modal-crop. modal-crop and the image need to be in the center of modal-area.

I can't use grid or flex because I need to support IE9.

 .modal { position: fixed; top: 0; right: 0; bottom: 0; left: 0; z-index: 1050; display: none; overflow: hidden; outline: 0; } .modal-area { position: absolute; top: 50%; left: 50%; width: 50%; height: 50%; transform: translate(-50%, -50%); margin: 0 auto; padding: 30px; background-color: blueviolet; border-radius: 4px; box-shadow: 0 0 50px black; overflow: hidden; } .modal-area img { margin-left: auto; margin-right: auto; } .modal-crop { position: relative; background-color: aliceblue; left: 0; right: 0; top: 0; margin-left: auto; margin-right: auto; width: 200px; height: 200px; opacity: 0.2; z-index: 2; } 

 <div class="modal"> <div class="modal-area"> <div class="modal-crop"></div> #img will be inserted here using Javascript# </div> </div> 

Answer 1

Your image need to be positionned absolutely like this :

 .modal { position: fixed; top: 0; right: 0; bottom: 0; left: 0; z-index: 1050; overflow: hidden; outline: 0; min-height: 300px; } .modal-area { position: absolute; top: 50%; left: 50%; width: 50%; height: 50%; transform: translate(-50%, -50%); margin: 0 auto; padding: 30px; background-color: blueviolet; border-radius: 4px; box-shadow: 0 0 50px black; overflow: hidden; } .modal-area img { margin-left: auto; margin-right: auto; position: absolute; top: 0; right: 0; left: 0; bottom: 0; } .modal-crop { position: relative; background-color: aliceblue; left: 0; right: 0; top: 0; margin-left: auto; margin-right: auto; height: 100%; opacity: 0.2; z-index: 2; } 

 <div class="modal"> <div class="modal-area"> <div class="modal-crop"></div> <img src="https://lorempixel.com/500/500/"> </div> </div> 

Answer 2

I think I got an understanding of what you want to achieve. And I also know that it can be a pain to overlap elements with absolute positioning in multiple layers (even more so when it comes to different browsers).

I recommend you to use a grid layout, which is quite easy to set up:

HTML

<div class="modal">
    <div class="modal-area">
        <img src="http://via.placeholder.com/200x200">
        <div class="modal-crop"></div>
    </div>
</div>

CSS

.modal {
position: fixed;
top: 0;
right: 0;
bottom: 0;
left: 0;
z-index: 1050;
display: block;
overflow: hidden;
outline: 0;
    }


.modal-area {
  display:grid;
  grid-template-rows: auto;
  grid-template-columns: auto;
  justify-items:center;
    position: absolute;
    top: 50%;
    left: 50%;
    width: 50%;
    height: 50%;
    transform: translate(-50%, -50%);
    margin: 0 auto;
    padding: 30px;
    background-color: blueviolet;
    border-radius: 4px;
    box-shadow: 0 0 50px black;
    overflow: hidden;
}

.modal-area img {
    grid-row: 1/span 1;
    grid-column: 1/span 1;
    z-index:1;
}


.modal-crop  {
  width: 200px;
  height: 200px;
  grid-row: 1/span 1;
  grid-column: 1/span 1;
  background-color: red;
  opacity: 0.2;
  z-index:2;
}

Be aware though, that in this solution the "modal crop" needs to be set to width and and height of the image. But I used similar solutions in other situations and will not be hard to adjust it so that it works for any image sizes.

Have a fiddle: https://jsfiddle.net/9odLnh7r/

Answer 3

The question is note very clear, but as far as I understand you need to add this css ruleset to your image:

 .modal { position: fixed; top: 0; right: 0; bottom: 0; left: 0; z-index: 1050; /* display: none; */ overflow: hidden; outline: 0; } .modal-area { position: absolute; top: 50%; left: 50%; width: 50%; height: 50%; transform: translate(-50%, -50%); margin: 0 auto; padding: 30px; background-color: blueviolet; border-radius: 4px; box-shadow: 0 0 50px black; overflow: hidden; } .modal-area img { margin-left: auto; margin-right: auto; } .modal-crop { position: relative; background-color: aliceblue; left: 0; right: 0; top: 0; margin-left: auto; margin-right: auto; width: 200px; height: 200px; opacity: 0.2; z-index: 2; } .centerMe { position: absolute; top: 50%; left: 50%; transform: translate(-50%, -50%); } 

 <div class="modal"> <div class="modal-area"> <div class="modal-crop"></div> <img class="centerMe" src="http://www.budgetstockphoto.com/bamers/stock_photo_spectrum.jpg"> </div> </div>