给多个单元格区域设置背景图

问题：如何给多个单元格区域设置背景图

SpreadJS支持给工作簿添加背景图，也支持给某一个单元格设置背景图。有小伙伴有这样的需求：给一片单元格区域设置背景图，这该如何实现呢？

解决思路

方案一：将这片单元格区域设置合并单元格，然后给这个合并单元格设置背景图。

sheet.getCell(0,0).backgroundImage("https://gcdn.grapecity.com.cn/uc_server/avatar.php?uid=52354&size=middle")

方案二：通过自定义单元格实现。

创建自定义单元格类型：

function WaterMarkCellType() {
    this.typeName = "WaterMarkCellType"
}
WaterMarkCellType.prototype = new GC.Spread.Sheets.CellTypes.Text();
WaterMarkCellType.prototype.paint = function (ctx, value, x, y, w, h, style, options) {
    //Paints a cell on the canvas. 
    var background = style.backgroundImage;
    style.backgroundImage = undefined;
    GC.Spread.Sheets.CellTypes.Text.prototype.paint.apply(this, arguments)
    GC.Spread.Sheets.CellTypes.Text.prototype.paint.call(this, ctx, undefined, x, y, w+100, h+100, {backgroundImage:background}, options)
};

给单元格区域的左上角单元格设置此单元格类型，背景图片由此绘制。

var spread = new GC.Spread.Sheets.Workbook(document.getElementById("ss"));
var sheet = spread.getActiveSheet();
sheet.getCell(3, 3).cellType(new WaterMarkCellType()).backgroundImage('https://www.grapecity.com.cn/images/metalsmith/home/logo_spjs.png')
sheet.setArray(2, 2, [[1,2,3,4,5,6,],[1,2,3,4,5,6,],[1,2,3,4,5,6,],[1,2,3,4,5,6,],[1,2,3,4,5,6,],[1,2,3,4,5,6,]])

解决滑动滚动条时，图片未完全绘制的问题。

之所以会出现这个问题，是由于Demo中是把单个单元格中的背景图进行了放大绘制，而当滚动条滚动到目标单元格下方时，目标单元格并未被绘制，此时就会出现问题。

解决办法是添加滚动条事件，在事件中注册setTimeout，将sheet重绘即可。setTimeout时间应控制在不影响视觉效果的情况下尽量长一些。

var setTimeoutId = null;
sheet.bind(GC.Spread.Sheets.Events.TopRowChanged, function (s, e) {
    clearTimeout(setTimeoutId);
    // 这里的间隔时间，在不影响视觉效果的情况下尽可能长一点
    setTimeoutId = setTimeout(function(){
        e.sheet.repaint();
    50);
});

最终效果如下：

完整Demo如下：

<!doctype html>
<html style="height:100%;font-size:14px;">

<head>
    <meta name="spreadjs culture" content="zh-cn" />
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <link rel="stylesheet" type="text/css" href="https://cdn.grapecity.com.cn/spreadjs/css/gc.spread.sheets.12.0.6.css">
    <script src="https://cdn.grapecity.com.cn/spreadjs/scripts/jquery-1.11.1.min.js" type="text/javascript"></script>
    <script type="text/javascript" src="http://cdn.grapecity.com/spreadjs/hosted/scripts/gc.spread.sheets.all.14.1.0.min.js"></script>
	<script src="http://cdn.grapecity.com/spreadjs/hosted/scripts/plugins/gc.spread.sheets.charts.14.1.0.min.js"></script>
	<script src="http://cdn.grapecity.com/spreadjs/hosted/scripts/plugins/gc.spread.sheets.shapes.14.1.0.min.js"></script>
	<script src="http://cdn.grapecity.com/spreadjs/hosted/scripts/plugins/gc.spread.sheets.print.14.1.0.min.js"></script>
	<script src="http://cdn.grapecity.com/spreadjs/hosted/scripts/plugins/gc.spread.sheets.barcode.14.1.0.min.js"></script>
	<script src="http://cdn.grapecity.com/spreadjs/hosted/scripts/plugins/gc.spread.sheets.pdf.14.1.0.min.js"></script>
    <script src="http://cdn.grapecity.com/spreadjs/hosted/scripts/interop/gc.spread.excelio.14.1.0.min.js"></script>
	<script src="http://cdn.grapecity.com/spreadjs/hosted/scripts/resources/zh/gc.spread.sheets.resources.zh.14.1.0.min.js"></script>

    <style>
        * {
            -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
        }

        .sample-tutorial {
            position: relative;
            height: 100%;
            overflow: hidden;
        }

        .sample-spreadsheets {
            width: calc(100% - 280px);
            height: 100%;
            overflow: hidden;
            float: left;
        }

        .group input {
            padding: 4px 12px;
        }
    </style>
</head>

<body style="margin:0;position:absolute;top:0;bottom:0;left:0;right:0;font-size:14px;user-select:none;-webkit-user-select: none;overflow:hidden;font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'">
    <div class="sample-tutorial">
        <div id="ss" class="sample-spreadsheets"></div>
    </div>
    <script type="text/javascript">
        function WaterMarkCellType() {
            this.typeName = "WaterMarkCellType"
        }
        WaterMarkCellType.prototype = new GC.Spread.Sheets.CellTypes.Text();
        WaterMarkCellType.prototype.paint = function (ctx, value, x, y, w, h, style, options) {
            //Paints a cell on the canvas. 
            var background = style.backgroundImage;
            style.backgroundImage = undefined;
            GC.Spread.Sheets.CellTypes.Text.prototype.paint.apply(this, arguments)
            GC.Spread.Sheets.CellTypes.Text.prototype.paint.call(this, ctx, undefined, x, y, w+100, h+100, {backgroundImage:background}, options)
        };

        $(document).ready(function () {
            var spread = new GC.Spread.Sheets.Workbook(document.getElementById("ss"));
            var sheet = spread.getActiveSheet();
            sheet.getCell(3, 3).cellType(new WaterMarkCellType()).backgroundImage('https://www.grapecity.com.cn/images/metalsmith/home/logo_spjs.png')

            sheet.setArray(2, 2, [[1,2,3,4,5,6,],[1,2,3,4,5,6,],[1,2,3,4,5,6,],[1,2,3,4,5,6,],[1,2,3,4,5,6,],[1,2,3,4,5,6,]])

            var setTimeoutId = null;
            sheet.bind(GC.Spread.Sheets.Events.TopRowChanged, function (s, e) {
                clearTimeout(setTimeoutId);
                // 这里的间隔时间，在不影响视觉效果的情况下尽可能长一点
                setTimeoutId = setTimeout(function(){
                    e.sheet.repaint();
                }, 50);
            });

        });
    </script>
</body>

</html>

作者: GrapeCity China | 审核：AlexZ | 更新时间：2023.09.26