alfresco-ng2-components/lib/core/viewer/components/img-viewer.theme.scss

@mixin adf-image-viewer-theme($theme) {
    $accent: map-get($theme, accent);
    $background: map-get($theme, background);
    $viewer-image-outline: 1px solid mat-color($accent, A200) !default;

    .adf-image-viewer {
        width: 100%;

        .adf-image-container {
            &:focus {
                outline-offset: -1px;
                outline: $viewer-image-outline;
            }
            display: flex;
            height: 90vh;
            align-items: center;
            justify-content: center;
            img {
                max-height: 100%;
                max-width: 100%;
            }
            /* query for Microsoft IE 11*/
            @media screen and (-ms-high-contrast: active), screen and (-ms-high-contrast: none) {
                img {
                    height: 100%;
                }
            }
        }

        &__toolbar {
            position: absolute;
            bottom: 5px;

            left: 50%;
            transform: translateX(-50%);

            .adf-toolbar .mat-toolbar {
                max-height: 48px;
                background-color: mat-color($background, card);
                border-width: 0;
                border-radius: 2px;
                box-shadow: 0 2px 2px 0 rgba(0, 0, 0, 0.24), 0 0 2px 0 rgba(0, 0, 0, 0.12);
            }

            .adf-main-toolbar {
                display: inline-block;
            }

            .adf-secondary-toolbar {
                display: inline-block;
                margin-left: 10px;
            }

        }
    }
}