Added placeholder loader

Author: usercode

src/ImageWizard.Client/Builder/PlaceholderExtensions.cs

@@ -0,0 +1,16 @@
+// Copyright (c) usercode
+// https://github.com/usercode/ImageWizard
+// MIT License
+
+namespace ImageWizard.Client;
+
+/// <summary>
+/// OpenGraphExtensions
+/// </summary>
+public static class PlaceholderExtensions
+{
+    public static Image Placeholder(this ILoader imageUrlBuilder, int width, int height)
+    {
+        return new Image(imageUrlBuilder.LoadData("placeholder", $"{width}x{height}"));
+    }
+}

src/ImageWizard.ImageSharp/Loaders/Placeholder/PalceholderExtensions.cs

@@ -0,0 +1,23 @@
+// Copyright (c) usercode
+// https://github.com/usercode/ImageWizard
+// MIT License
+
+using Microsoft.Extensions.DependencyInjection;
+
+namespace ImageWizard.ImageSharp;
+
+public static class PalceholderExtensions
+{
+    public static IImageWizardBuilder AddPlaceholder(this IImageWizardBuilder wizardConfiguration, Action<PlaceholderOptions>? options = null)
+    {
+        if (options != null)
+        {
+            wizardConfiguration.Services.Configure(options);
+        }
+
+        wizardConfiguration.Services.AddTransient<PlaceholderLoader>();
+        wizardConfiguration.LoaderManager.Register<PlaceholderLoader>("placeholder");
+
+        return wizardConfiguration;
+    }
+}

src/ImageWizard.ImageSharp/Loaders/Placeholder/PlaceholderLoader.cs

@@ -0,0 +1,60 @@
+// Copyright (c) usercode
+// https://github.com/usercode/ImageWizard
+// MIT License
+
+using ImageWizard.Loaders;
+using Microsoft.Extensions.Options;
+using SixLabors.Fonts;
+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.Drawing.Processing;
+using SixLabors.ImageSharp.PixelFormats;
+using SixLabors.ImageSharp.Processing;
+using System.Text.RegularExpressions;
+
+namespace ImageWizard.ImageSharp;
+
+public partial class PlaceholderLoader : Loader<PlaceholderOptions>
+{
+    public PlaceholderLoader(IOptions<PlaceholderOptions> options)
+        : base(options)
+    {
+    }
+
+    [GeneratedRegex("^(?<width>[0-9]+)x(?<height>[0-9]+)$")]
+    private partial Regex RegexSource();
+
+    public override async Task<LoaderResult> GetAsync(string source, ICachedData? existingCachedData)
+    {
+        Match match = RegexSource().Match(source);
+
+        if (match.Success == false)
+        {
+            return LoaderResult.Failed();
+        }
+
+        int width = int.Parse(match.Groups["width"].Value);
+        int height = int.Parse(match.Groups["height"].Value);
+
+        Image image = new Image<Rgba32>(width, height, Rgba32.ParseHex(Options.Value.BackgroundColor));
+
+        string text = $"{width}x{height}";
+
+        var font = SystemFonts.Get(Options.Value.FontName).CreateFont(Options.Value.FontSize, FontStyle.Regular);
+        var textOptions = new TextOptions(font) { Dpi = 72, KerningMode = KerningMode.Standard };
+        var rect = TextMeasurer.MeasureSize(text, textOptions);
+
+        image.Mutate(x => x.DrawText(
+                             $"{image.Width} x {image.Height}",
+                            font,
+                            new Color(Rgba32.ParseHex(Options.Value.FontColor)),
+                            new PointF((image.Width / 2) - (rect.Width / 2), (image.Height / 2) - (rect.Height / 2) )));
+
+        MemoryStream mem = new MemoryStream();
+        
+        await image.SaveAsPngAsync(mem);
+        
+        mem.Seek(0, SeekOrigin.Begin);
+
+        return LoaderResult.Success(new OriginalData(MimeTypes.Png, mem));
+    }
+}

src/ImageWizard.ImageSharp/Loaders/Placeholder/PlaceholderOptions.cs

@@ -0,0 +1,19 @@
+// Copyright (c) usercode
+// https://github.com/usercode/ImageWizard
+// MIT License
+
+using ImageWizard.Loaders;
+
+namespace ImageWizard.ImageSharp;
+
+public class PlaceholderOptions : LoaderOptions
+{
+    public string BackgroundColor { get; set; } = "#4682b4";
+
+    public string FontColor { get; set; } = "#FFFFFF";
+
+    public string FontName { get; set; } = "Arial";
+
+    public float FontSize { get; set; } = 32;
+
+}

src/ImageWizard.TestApp/Pages/Index.cshtml

@@ -193,6 +193,17 @@
         </div>
     </div>
 
+    <h2>Placeholder</h2>
+    <p>@@Url.ImageWizard().Placeholder(600, 300).BuildUrl()</p>
+    <p>@Url.ImageWizard().Placeholder(600, 300).BuildUrl()</p>
+
+    <div class="row">
+        <div class="col">
+            <img src="@Url.ImageWizard().Placeholder(600, 300).BuildUrl()" />
+            <p>600x300</p>
+        </div>
+    </div>   
+
     <h2>DPR (Device Pixel Ratio)</h2>
 
     <p>@@Url.ImageWizard().Fetch("lion.jpg").AsImage().DPR(1).Resize(100,100).BuildUrl()</p>
@@ -261,7 +272,7 @@
         </div>
     </div>
 
-    <h2>Use youtube taghelper (DSGVO friendly)</h2>
+    <h2>Use youtube taghelper (GDPR friendly)</h2>
 
    <div class="alert alert-secondary">
         @("<youtube video-id=\"AQHZQ8p6FCA\" width=\"1920\" height=\"1080\" grayscale=\"true\" blur=\"true\" use-no-cookie=\"true\" />")

src/ImageWizard.TestApp/Program.cs

@@ -119,6 +119,7 @@
             .AddPuppeteerLoader(x => x.RefreshMode = LoaderRefreshMode.None)
             //.AddPlaywrightLoader(x => x.RefreshMode = LoaderRefreshMode.None)
             .AddOpenGraphLoader(x => x.RefreshMode = LoaderRefreshMode.None)
+            .AddPlaceholder(x => x.RefreshMode = LoaderRefreshMode.None)
             .AddFFMpegCore()
             .AddDocNET()
             .AddOpenCvSharp()