masonry_gallery_rows.css

body {
    overflow-y: scroll;
}

.masonry-gallery-rows {
    padding: 0;
    display: -webkit-box;
    display: -ms-flexbox;
    display: flex;
    -webkit-box-orient: horizontal;
    -webkit-box-direction: normal;
    -ms-flex-direction: row;
    flex-direction: row;
    -ms-flex-wrap: wrap;
    flex-wrap: wrap;
    -webkit-box-align: start;
    -ms-flex-align: start;
    align-items: flex-start;
    -ms-flex-line-pack: start;
    align-content: flex-start;
    opacity: 0;
}

.masonry-gallery-rows img { /*Here you can change paddings, borders and margins of images*/
    padding: 2px;
    /*border: 2px solid #ccc;*/
    /*margin: 5px;*/
    border-radius: 5px;
    height: 300px;
}

/*Styles for anchors and captions*/
.thumbnail-item {
    position: relative;
    padding: 0;
    margin: 0;
}
.thumbnail-item img {
    display: block;
    -webkit-transition-duration: 0.5s;
    transition-duration: 0.5s;
}
.caption-center {
    width: 100%;
    position: absolute;
    top: 50%;
    left: 0;
    -webkit-transform: translateY(-50%);
    transform: translateY(-50%);
    text-align: center;
}
.caption-center p {
    padding: 20px;
    color: white;
    font-size: 18px;
    opacity: 0.3;
    -webkit-transition-duration: 0.1s;
    transition-duration: 0.1s;
}
.thumbnail-item:hover img {
    -webkit-filter: grayscale(100%) brightness(90%);
    filter: grayscale(100%) brightness(90%);
}
.thumbnail-item:hover p {
    opacity: 1;
}