kb(qrcode): Add KB for Barcode, QRCode and Chart export to image

components/barcodes/barcode/overview.md

@@ -133,5 +133,6 @@ The nested `BarcodePadding` tag exposes parameters that enable you to customize
 
 ## See Also
 
-  * [Live Demo: Barcode](https://demos.telerik.com/blazor-ui/barcode/overview)
-  * [Live Demo: Barcode Encoding](https://demos.telerik.com/blazor-ui/barcode/encodings)
+* [Live Demo: Barcode](https://demos.telerik.com/blazor-ui/barcode/overview)
+* [Live Demo: Barcode Encoding](https://demos.telerik.com/blazor-ui/barcode/encodings)
+* [Export Barcode to Image]({%slug qrcode-barcode-chart-kb-export-to-image%})

components/barcodes/qrcode/overview.md

@@ -94,4 +94,5 @@ The nested `QRCodeBorder` tag exposes parameters that enable you to customize th
 
 ## See Also
 
-  * [Live Demo: QRCode](https://demos.telerik.com/blazor-ui/qrcode/overview)
+* [Live Demo: QRCode](https://demos.telerik.com/blazor-ui/qrcode/overview)
+* [Export QRCode to Image]({%slug qrcode-barcode-chart-kb-export-to-image%})

knowledge-base/qrcode-barcode-chart-export-to-image.md

@@ -0,0 +1,263 @@
+---
+title: Export QRCode, Barcode, or Chart to Image
+description: Learn how to convert and export a Telerik Blazor QRCode, Barcode, or Chart to an image and send it to the .NET runtime.
+type: how-to
+page_title: How to Export Telerik QRCode, Barcode, or Chart to Image
+slug: qrcode-barcode-chart-kb-export-to-image
+tags: telerik, blazor, qrcode, barcode, chart
+ticketid: 1572189, 1588186, 1667798
+res_type: kb
+---
+
+## Environment
+
+<table>
+    <tbody>
+        <tr>
+            <td>Product</td>
+            <td>
+                QRCode for Blazor, <br />
+                Barcode for Blazor, <br />
+                Chart for Blazor
+            </td>
+        </tr>
+    </tbody>
+</table>
+
+## Description
+
+This KB answers the following questions:
+
+* How to export a generated QRCode to a PNG or JPG image for saving on the server or download?
+* How to create an image from the Telerik QRCode for Blazor?
+* How to convert a Barcode, Chart, or QRCode from SVG to an image?
+* How to save a Barcode or QRCode as an image?
+
+## Solution
+
+Use `JSInterop` and JavaScript APIs to convert the Telerik component to a Base64 string and send it to the server.
+
+When using the `Canvas` `RenderingMode` of the Telerik component (Barcode, Chart, QRCode), use the [`toDataURL`](https://developer.mozilla.org/en-US/docs/Web/API/HTMLCanvasElement/toDataURL) method of the `canvas` HTML element to obtain a Base64 data URI for the image.
+
+When using the `SVG` rendering mode:
+
+1. Use an [`XMLSerializer`](https://developer.mozilla.org/en-US/docs/Web/API/XMLSerializer) to create an image [`Blob`](https://developer.mozilla.org/en-US/docs/Web/API/Blob).
+1. Create a `canvas` element and [get its 2D context](https://developer.mozilla.org/en-US/docs/Web/API/HTMLCanvasElement/getContext).
+1. [Draw the image](https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/drawImage) into the `canvas` element.
+1. Use the [`toDataURL`](https://developer.mozilla.org/en-US/docs/Web/API/HTMLCanvasElement/toDataURL) method of the `canvas` HTML element to obtain a Base64 data URI for the image.
+
+> When using a Blazor app with **Server** render mode, make sure to [increase the SignalR max message size]({%slug common-kb-increase-signalr-max-message-size%}), otherwise the Base64 data URI may not reach the .NET runtime.
+
+>caption Export QRCode, BarCode or Chart to Image
+
+````CSHTML
+@inject IJSRuntime js
+
+<TelerikButtonGroup SelectionMode="@ButtonGroupSelectionMode.Single">
+    <ButtonGroupToggleButton Selected="@(RenderingMode == RenderingMode.SVG)"
+                             OnClick="@( () => ToggleRenderingMode(RenderingMode.SVG) )">
+        Use SVG
+    </ButtonGroupToggleButton>
+    <ButtonGroupToggleButton Selected="@(RenderingMode == RenderingMode.Canvas)"
+                             OnClick="@( () => ToggleRenderingMode(RenderingMode.Canvas) )">
+        Use Canvas
+    </ButtonGroupToggleButton>
+</TelerikButtonGroup>
+
+<TelerikButton ThemeColor="@ThemeConstants.Button.ThemeColor.Success"
+               OnClick="@OnQrCodeExportButtonClick">Export to PNG</TelerikButton>
+
+<div style="display: flex; gap: 2em;">
+    <div style="flex: 1 33%;">
+        <h3>@RenderingMode QR Code</h3>
+        <TelerikQRCode RenderAs="@RenderingMode"
+                       Size="240px"
+                       Value="https://docs.telerik.com/blazor-ui/introduction"
+                       Class="exportable-qrcode">
+        </TelerikQRCode>
+
+        @if (!string.IsNullOrEmpty(QrImageDataUrl))
+        {
+            <h3>QR Code PNG</h3>
+            <img src="@QrImageDataUrl" style="width: 240px;" alt="PNG from QR Code" />
+        }
+
+    </div>
+    <div style="flex: 1 66%;">
+        <h3>@RenderingMode Chart</h3>
+        <TelerikChart RenderAs="@RenderingMode"
+                      Height="240px"
+                      Class="exportable-chart">
+            <ChartSeriesItems>
+                <ChartSeries Type="ChartSeriesType.Column"
+                             Data="@SeriesData1"
+                             Field="@nameof(ChartModel.Revenue)"
+                             CategoryField="@nameof(ChartModel.TimePeriod)"
+                             Name="Product 1">
+                </ChartSeries>
+                <ChartSeries Type="ChartSeriesType.Line"
+                             Data="@SeriesData2"
+                             Field="@nameof(ChartModel.Revenue)"
+                             CategoryField="@nameof(ChartModel.TimePeriod)"
+                             Name="Product 2">
+                </ChartSeries>
+            </ChartSeriesItems>
+
+            <ChartCategoryAxes>
+                <ChartCategoryAxis Type="@ChartCategoryAxisType.Date"></ChartCategoryAxis>
+            </ChartCategoryAxes>
+
+            <ChartValueAxes>
+                <ChartValueAxis Max="1000" />
+            </ChartValueAxes>
+
+            <ChartTitle Text="Chart"></ChartTitle>
+
+            <ChartLegend Position="ChartLegendPosition.Bottom">
+            </ChartLegend>
+        </TelerikChart>
+        @if (!string.IsNullOrEmpty(ChartImageDataUrl))
+        {
+            <h3>Chart PNG</h3>
+            <img src="@ChartImageDataUrl" style="width: 100%;" alt="PNG from Chart" />
+        }
+    </div>
+</div>
+
+@* Move JavaScript code to a separate JS file *@
+<script suppress-error="BL9992">
+    function getImageFromCanvas(selector) {
+        const canvas = document.querySelector(`${selector} canvas`);
+        if (canvas) {
+            return canvas.toDataURL("image/png");
+        }
+    }
+
+    function getImageFromSvg(selector) {
+        const dpr = window.devicePixelRatio;
+
+        const svg = document.querySelector(`${selector} svg`);
+        if (!svg) {
+            return;
+        }
+
+        const svgBox = svg.getBBox();
+        const svgW = svgBox.width;
+        const svgH = svgBox.height;
+
+        const svgData = (new XMLSerializer()).serializeToString(svg);
+        const svgBlob = new Blob([svgData], {
+            type: "image/svg+xml;charset=utf-8"
+        });
+        const blobUrl = URL.createObjectURL(svgBlob);
+
+        return getBlobImage(blobUrl, svgW, svgH).then((img) => {
+            const canvas = document.createElement("canvas");
+            canvas.width = svgW * dpr;
+            canvas.height = svgH * dpr;
+
+            const context = canvas.getContext("2d");
+            context.imageSmoothingEnabled = false;
+            context.drawImage(img, 0, 0, svgW * dpr, svgH * dpr);
+
+            URL.revokeObjectURL(blobUrl);
+            img.parentElement.removeChild(img);
+
+            return canvas.toDataURL("image/png");
+        });
+    }
+
+    function getBlobImage(blobUrl, imageWidth, imageHeight) {
+        return new Promise(function(resolve) {
+            const img = new Image();
+
+            img.addEventListener("load", () => {
+                setTimeout( () => resolve(img) );
+            });
+
+            img.style.cssText = "visibility:hidden;position:absolute;top:0;left:0;";
+            img.width = imageWidth;
+            img.height = imageHeight;
+            document.body.appendChild(img);
+
+            img.src = blobUrl;
+        });
+    }
+</script>
+
+@code {
+    #nullable enable
+
+    private RenderingMode RenderingMode { get; set; } = RenderingMode.SVG;
+
+    private string QrImageDataUrl { get; set; } = string.Empty;
+    private string ChartImageDataUrl { get; set; } = string.Empty;
+
+    private List<ChartModel> SeriesData1 { get; set; } = new();
+    private List<ChartModel> SeriesData2 { get; set; } = new();
+
+    private async Task OnQrCodeExportButtonClick()
+    {
+        string jsFunctionName = RenderingMode == RenderingMode.SVG ? "getImageFromSvg" : "getImageFromCanvas";
+
+        QrImageDataUrl = await js.InvokeAsync<string>(jsFunctionName, ".exportable-qrcode");
+        ChartImageDataUrl = await js.InvokeAsync<string>(jsFunctionName, ".exportable-chart");
+    }
+
+    private void ToggleRenderingMode(RenderingMode newMode)
+    {
+        RenderingMode = newMode;
+
+        QrImageDataUrl = ChartImageDataUrl = string.Empty;
+    }
+
+    #region Data Generation
+
+    protected override async Task OnInitializedAsync()
+    {
+        var now = DateTime.Today;
+        var monthsBack = 6;
+
+        for (int i = 1; i <= monthsBack; i++)
+        {
+            var dateTimeValue = now.AddMonths(-monthsBack + i);
+
+            SeriesData1.Add(new ChartModel()
+            {
+                Id = i,
+                Product = "Product 1",
+                Revenue = Random.Shared.Next(1, 900),
+                TimePeriod = dateTimeValue
+            });
+
+            SeriesData2.Add(new ChartModel()
+            {
+                Id = i,
+                Product = "Product 2",
+                Revenue = Random.Shared.Next(1, 900),
+                TimePeriod = dateTimeValue
+            });
+        }
+
+        await base.OnInitializedAsync();
+    }
+
+    public class ChartModel
+    {
+        public int Id { get; set; }
+        public string Product { get; set; } = string.Empty;
+        public DateTime TimePeriod { get; set; }
+        public decimal Revenue { get; set; }
+    }
+
+    #endregion Data Generation
+}
+````
+
+> The example in this KB article demonstrates non-Telerik JavaScript APIs, which are not subject to Telerik technical support.
+
+## See Also
+
+* [Barcode Overview]({%slug barcode-overview%})
+* [Chart Overview]({%slug components/chart/overview%})
+* [QRCore Overview]({%slug qrcode-overview%})