Unicode 艺术

class ThreadWrapper {

    internal ThreadWrapper(
        PreviewWindow presentation,
        Image image,
        Main.Renderer renderer, BitmapImage source,
        Typeface typeface, int fontSize,
        Dispatcher dispatcher) {
            this.presentation = presentation;
            this.image = image;
            this.typeface = typeface;
            this.fontSize = fontSize;
            this.renderer = renderer;
            this.source = source;
            source.Freeze();
            this.dispatcher = dispatcher;
    } //ThreadWrapper

    internal void Start() {
        thread = new Thread(Body);
        thread.TrySetApartmentState(ApartmentState.STA);
        thread.Start();
    } //Start

    internal void Abort() {
        thread.Abort();
    } //Abort

    internal void Join() {
        thread.Join();
    } //Join

    void Body() {
        try {
            ImageSource imageSource = renderer.Render(source, typeface, fontSize, 0);
            dispatcher.Invoke(new System.Action(() => {
                image.Source = imageSource;
                image.Width = source.Width * fontSize;
                image.Height = source.Height * fontSize;
                presentation.menu.Visibility = Visibility.Visible;
                presentation.SetTarget(RenderTarget.scaled);
            }));
        } catch (ThreadAbortException) {
        } catch (System.Exception e) {
            dispatcher.Invoke(
                new System.Action<Exception>((Exception exception) => {
                    presentation.ShowException(exception);
                }), e);
        } //exception
    } //Body

    Thread thread;
    Dispatcher dispatcher;
    Main.Renderer renderer;
    BitmapImage source;
    PreviewWindow presentation;
    Image image;
    Typeface typeface;
    int fontSize;

} //class ThreadWrapper

请注意，线程可以异步中止，这有时会遭到其他开发人员的强烈反对。这是一个太大太复杂的主题，无法在此详述，因此我将仅声明：我以特定于每个应用程序的安全方式来执行此操作。

关于多线程的一个重要点是线程同步。在当前应用程序中，有两个地方需要在这两个线程之间传递数据：UI 线程和渲染每个预览实例的线程。首先，输入图像的引用被传递给图像渲染线程。最后，渲染后的ImageSource被传递给 UI 线程进行显示，作为Image.Source属性。这两个转换都基于Freeze方法：请参阅System.Windows.Freezable.Freeze。

HTML 渲染

乍一看，人们可能会认为文本和 HTML 呈现 Unicode 艺术很容易实现。然而，我第一次尝试就搞砸了。以下是遗漏的几点：

1. 字符集中的某些字符可能不受特定字体支持。在位图渲染中，这不会造成大问题，因为所有字符都在输出位图的相同固定区域内渲染。在 HTML 中，这些字符可能仍会显示并占用一些空间，但即使是等宽字体，其宽度也可能不同，这会导致文本行的水平偏移。
2. 意外的是，某些字符可能充当行尾字符。对于 HTML 的pre元素，这会导致换行，可能在步长的中间。
3. 意外的是，某些字符序列可能匹配 HTML 字符实体。

前两个问题应该在构建字符集时解决。重要的是要自动过滤掉一些字符。这是CharacterRepertoire.Build的片段：

internal void Build(Typeface typeface) {
    GlyphTypeface glyphTypeface;
    bool success = typeface.TryGetGlyphTypeface(out glyphTypeface);
    var map = glyphTypeface.CharacterToGlyphMap;            
    System.Predicate<ushort> isCharacterSupported = (codePoint) => {
        ushort glyphIndexDummy;
        return map.TryGetValue(codePoint, out glyphIndexDummy);
    }; //isCharacterSupported
    CharacterList list = new CharacterList();
    DoubleList brightnessList = new DoubleList();
    foreach (var range in DefinitionSet.charset)
        for (ushort codePoint = range.first;
            codePoint <= range.last;
            ++codePoint)
        {
            if (!isCharacterSupported(codePoint)) continue;
            char character = System.Char.ConvertFromUtf32(codePoint)[0];
            if (char.IsSeparator(character) ||
                char.IsControl(character))
                    continue;
            list.Add(character);
            brightnessList.Add(GetBrightness(character, typeface));
        } //loop
    // ...
}; //Build

internal void SaveToHtml(
        string fileName,
        string originalFileName,
        Typeface typeface, int fontSize)
{
    if (originalFileName == null) originalFileName = string.Empty;
    int xMax = unicodePixels.GetUpperBound(1);
    int yMax = unicodePixels.GetUpperBound(0);
    StringBuilder sb = new StringBuilder();
    for (var indexY = 0; indexY <= yMax; ++indexY) {
        for (var indexX = 0; indexX <= xMax; ++indexX)
            sb.Append(unicodePixels[indexY, indexX]);
        if (indexY < yMax) sb.Append(System.Environment.NewLine);
    } //loop Y
    GlyphTypeface glyphTypeface;
    typeface.TryGetGlyphTypeface(out glyphTypeface);
    System.Collections.Generic.IDictionary<ushort, double>
        advanceHeights = glyphTypeface.AdvanceHeights;
    System.Collections.Generic.IDictionary<ushort,
        double> advanceWidths = glyphTypeface.AdvanceWidths;
    double aspect = 1;
    double width, height;
    ushort testCharachter = DefinitionSet.fullSizeSampleCharacter;
    if (advanceWidths.TryGetValue(testCharachter, out width) &&
        advanceHeights.TryGetValue(testCharachter, out height))
            // then sample character is supported by typeface
            aspect = width / height;
    string html = string.Format(
        Resources.Resources.HtmlFormat,
        originalFileName,
        1,
        aspect,
        typeface.FontFamily.ToString(),
        System.Web.HttpUtility.HtmlEncode(sb.ToString()));  
    using (StreamWriter writer =
        new StreamWriter(fileName, false, Encoding.UTF8)) {
        writer.WriteLine(html);
    } //using
} //SaveToHtml

<html>
<head>
    <title>Unicode Art</title>
    <meta name="generator" content="UnicodeArt.exe" />
    <meta name="description"
    content="Generated from file: input.cow.png; ..." />
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <style type="text/css">
        pre {
        font-size: 1em;
        line-height: 0.748933577087142em;
        font-family: "Courier New", monospace;
    }
    </style>
</head>
<body>

<pre><!-- image characters go here... --></pre>

</body>
</html>

[STAThread]
static void Main(string[] args) {
    using (var iconStream = new System.IO.MemoryStream()) {
        TheApplication app = new TheApplication();
        UnicodeArt.Resources.Resources.IconMain.Save(iconStream);
        iconStream.Seek(0, System.IO.SeekOrigin.Begin);
        app.ApplicationIcon =
            System.Windows.Media.Imaging.BitmapFrame.Create(iconStream);
        app.Run();
    } //using
} //Main

protected override void OnStartup(StartupEventArgs e) {
    // ...
    MainWindow = new Ui.MainWindow();
    MainWindow.Title = ProductName;
    MainWindow.Icon = ApplicationIcon;
    MainWindow.Show();
    // ...
} //OnStartup