图片上传时预浏览设置

<%= f.input :avatar, label: "图标:", as: :file %>
$("#production_avatar").removeClass('file').fileinput({
        overwriteInitial: true,
        maxFileSize: 1500,
        showClose: false,
        showCaption: false,
        zoomIcon: false,
        browseLabel: '',
        removeLabel: '',
        browseIcon: '<i class="glyphicon glyphicon-folder-open"></i>',
        removeIcon: '<i class="glyphicon glyphicon-remove"></i>',
        removeTitle: '取消',
        elErrorContainer: false,
        msgErrorClass: 'alert alert-block alert-danger',
        defaultPreviewContent: '<img src="/assets/default_avatar.jpg" alt="" style="width:160px">',
        layoutTemplates: {main2: '{preview} {remove} {browse}', footer: ''},
        allowedFileExtensions: ["jpg", "jpeg", "png", "gif"],
        <% if @production && !@production.avatar.blank? %>
        initialPreview: [ //预览图片的设置
            '<img src="<%= @production.avatar %>" class="file-preview-image" alt="" style="width:160px">',
        ]
        <% end %>
    }).on('fileerror', function (event, data, msg) {
        alert('请选择图片文件！')
    });