discourse/app/assets/stylesheets/common/base/upload.scss

.uploaded-image-preview {
  background: var(--primary-medium) center;
  background-size: cover;
  position: relative;

  .placeholder-overlay {
    background-size: contain;
    background-repeat: no-repeat;
    background-position: center;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    opacity: 0.3;
  }

  .image-upload-controls {
    position: relative;
    display: flex;
    padding: 10px;

    .btn {
      margin-right: 5px;
      padding: 7px 10px;
    }

    .image-uploader-lightbox-btn {
      background: none;
      margin-right: 0;
      margin-left: auto;

      .d-icon {
        color: var(--primary-low);
      }

      &:hover {
        background: none;

        .d-icon {
          color: var(--primary);
        }
      }
    }
  }
}

.image-uploader.no-repeat {
  .uploaded-image-preview {
    background-repeat: no-repeat;
  }
}

.image-uploader.contain-image {
  .uploaded-image-preview {
    background-size: contain;
  }
}

.hidden-upload-field {
  visibility: hidden;
  position: absolute;
}