Paint.Net笔记(X4) Effect

Posted on | In

上一篇讲菜单项中的Action 与 HistoryFunction. 两者之间的区别, 暂时还不甚了然. 先放一放, 这一篇整理一下Paint.Net中的Effect

Effect是以Plugin的方式提供的, 可以使用单独的dll, 放在特定的目录下. 程序启动时, 会自动加载.但Paint.Net并不是插件结构. 和SharpDevelop不同, SharpDevelop中界面的UI也是以Plugin的方式提供的.

Effect滤镜的主要逻辑在EffectMenuBase.cs中

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private void EffectMenuItem_Click(object sender, EventArgs e)
{
	if (AppWorkspace.ActiveDocumentWorkspace == null)
	{
		return; 
	}

	PdnMenuItem pmi = (PdnMenuItem)sender;
	Type effectType = (Type)pmi.Tag;

	RunEffect(effectType);
}

public void RunEffect(Type effectType)
{
	bool oldDirtyValue = AppWorkspace.ActiveDocumentWorkspace.Document.Dirty;
	bool resetDirtyValue = false;

	AppWorkspace.Update(); // make sure the window is done 'closing'
	AppWorkspace.Widgets.StatusBarProgress.ResetProgressStatusBar();
	DocumentWorkspace activeDW = AppWorkspace.ActiveDocumentWorkspace;

	PdnRegion selectedRegion; //选择区域，滤镜是应用于整幅图像，还是一个选择区域。下图就是只应用于一个选择区域

	if (activeDW.Selection.IsEmpty)
	{
		selectedRegion = new PdnRegion(activeDW.Document.Bounds);
	}
	else
	{
		selectedRegion = activeDW.Selection.CreateRegion();
	}

这里Effect通过EffectFlags.Configurable分为2类（有没有参数配置，可以调整参数）

第一类（没有参数配置）：

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if (!(effect.CheckForEffectFlags(EffectFlags.Configurable)))
{
	Surface copy = activeDW.BorrowScratchSurface(this.GetType() + ".RunEffect() using scratch surface for non-configurable rendering");

	try
	{
		using (new WaitCursorChanger(AppWorkspace))
		{
			copy.CopySurface(layer.Surface);
		}

		EffectEnvironmentParameters eep = new EffectEnvironmentParameters(
			AppWorkspace.AppEnvironment.PrimaryColor,
			AppWorkspace.AppEnvironment.SecondaryColor,
			AppWorkspace.AppEnvironment.PenInfo.Width,
			selectedRegion,
			copy);

		effect.EnvironmentParameters = eep;

		DoEffect(effect, null, selectedRegion, selectedRegion, copy, out exception);
	}

	finally
	{
		activeDW.ReturnScratchSurface(copy);
	}
}

第二类（有参数配置）:有参数配置，就需要一个调整参数的对话框，例如上图中的高斯模糊. 先是创建一个EffectConfigDialog

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using (EffectConfigDialog configDialog = effect.CreateConfigDialog())
{
	configDialog.Opacity = 0.9;
	configDialog.Effect = effect;
	configDialog.EffectSourceSurface = originalSurface;
	configDialog.Selection = selectedRegion;

	BackgroundEffectRenderer ber = null;

	EventHandler eh =
		delegate(object sender, EventArgs e)
		{
			EffectConfigDialog ecf = (EffectConfigDialog)sender;

			if (ber != null)
			{
				AppWorkspace.Widgets.StatusBarProgress.ResetProgressStatusBarAsync();

				try
				{
					ber.Start();
				}

				catch (Exception ex)
				{
					exception = ex;
					ecf.Close();
				}
			}
		};

	configDialog.EffectTokenChanged += eh;
}

如何创建EffectConfigDialog应该是Paint.Net中最有技巧性的东西了，真是大开眼界

翻看了不少代码，大致明白了是怎么回事。因为Effect在Paint.Net中是以plugin的形式存在，假如Effect有参数可以调整，那么在什么地方去调整参数呢？想像一下，我们需要有一个参数的Dialog。在没有源码的情况下，如何创建这个Dialog。以高斯模糊为例，只要该Effect提供参数，由Paint.Net帮你创建EffectConfigDialog

Paint.Net在框架中提供了一种参数与Control的一一对应，然后根据参数列表，创建一个一个的Control，然后用一个Panel将这些Control添加进来。再提供一个参数变更引发的事件。
这些参数用一个叫做EffectConfigToken的类封装起来(具体是PropertyCollection)

以高斯模糊为例

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public sealed class GaussianBlurEffect
    : InternalPropertyBasedEffect

public abstract class InternalPropertyBasedEffect
    : PropertyBasedEffect

public abstract class PropertyBasedEffect
    : Effect<PropertyBasedEffectConfigToken>

public sealed class PropertyBasedEffectConfigToken
    : EffectConfigToken

其中

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internal sealed class PropertyBasedEffectConfigDialog
    : EffectConfigDialog<PropertyBasedEffect, PropertyBasedEffectConfigToken>

AmountEffectConfigDialog.cs

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private void amountUpDown_ValueChanged(object sender, System.EventArgs e)
{
    if (amountTrackBar.Value != (int)amountUpDown.Value)
    {
        amountTrackBar.Value = (int)amountUpDown.Value;
        FinishTokenUpdate();
    }
}

public void FinishTokenUpdate()
{
    InitTokenFromDialog();
    OnEffectTokenChanged();
}

protected virtual void OnEffectTokenChanged()
{
    if (EffectTokenChanged != null)
    {
        EffectTokenChanged(this, EventArgs.Empty);
    }
}

扫描有多少个Effect，这部分是以插件的形式出现的，加载后出现在菜单项中

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private static EffectsCollection GatherEffects()
{
    List<Assembly> assemblies = new List<Assembly>();

    // PaintDotNet.Effects.dll
    assemblies.Add(Assembly.GetAssembly(typeof(Effect)));

    // TARGETDIR\Effects\*.dll
    string homeDir = PdnInfo.GetApplicationDir();
    string effectsDir = Path.Combine(homeDir, InvariantStrings.EffectsSubDir);
    bool dirExists;

    try
    {
        dirExists = Directory.Exists(effectsDir);
    }

    catch
    {
        dirExists = false;
    }

    if (dirExists)
    {
        string fileSpec = "*" + InvariantStrings.DllExtension;
        string[] filePaths = Directory.GetFiles(effectsDir, fileSpec);

        foreach (string filePath in filePaths)
        {
            Assembly pluginAssembly = null;

            try
            {
                pluginAssembly = Assembly.LoadFrom(filePath);
                assemblies.Add(pluginAssembly);
            }

            catch (Exception ex)
            {
                Tracing.Ping("Exception while loading " + filePath + ": " + ex.ToString());
            }
        }
    }

    EffectsCollection ec = new EffectsCollection(assemblies);
    return ec;
}