如何为InkCanvas画笔颜色设置笔触不透明度？如何设置UWP中墨迹笔触不透明度？

Hey there! Let's tackle both of your ink opacity questions one by one—super straightforward once you know where to look.

In WPF, the InkCanvas uses DrawingAttributes to control all stroke-related properties, including opacity. You can set this either directly in XAML or through code-behind:

XAML Approach #

Just define the DrawingAttributes inline within your InkCanvas, and set the Opacity property (values range from 0.0 for fully transparent to 1.0 for fully opaque):

<InkCanvas>
    <InkCanvas.DefaultDrawingAttributes>
        <DrawingAttributes Color="Blue" Opacity="0.5" />
    </InkCanvas.DefaultDrawingAttributes>
</InkCanvas>

Code-Behind Approach #

If you need to adjust opacity dynamically (like responding to a slider input), create a DrawingAttributes instance, set its properties, and assign it to the InkCanvas's DefaultDrawingAttributes:

// Initialize DrawingAttributes with desired opacity
var drawingAttrs = new DrawingAttributes
{
    Color = Colors.Red,
    Opacity = 0.3, // 30% opacity
    Width = 5,
    Height = 5
};

// Assign to your InkCanvas control
myInkCanvas.DefaultDrawingAttributes = drawingAttrs;

UWP's InkCanvas relies on the InkPresenter to manage stroke settings, and it uses DrawingAttributes (from the Windows.UI.Input.Inking namespace) to control opacity. Here's how to implement it:

XAML Approach #

You can set default stroke attributes directly on the InkPresenter nested inside your InkCanvas:

<InkCanvas>
    <InkCanvas.InkPresenter>
        <InkPresenter>
            <InkPresenter.DefaultDrawingAttributes>
                <DrawingAttributes Color="Green" Opacity="0.6" />
            </InkPresenter.DefaultDrawingAttributes>
        </InkPresenter>
    </InkCanvas.InkPresenter>
</InkCanvas>

Code-Behind Approach #

For dynamic opacity changes, create a DrawingAttributes object, configure the Opacity property, and assign it to the InkPresenter's DefaultDrawingAttributes:

using Windows.UI.Input.Inking;

// Create and configure DrawingAttributes
var inkAttrs = new DrawingAttributes
{
    Color = Windows.UI.Colors.Purple,
    Opacity = 0.4, // 40% transparency
    Size = new Windows.Foundation.Size(8, 8)
};

// Assign to your InkCanvas's InkPresenter
myInkCanvas.InkPresenter.DefaultDrawingAttributes = inkAttrs;

Quick side note: If you want to adjust the opacity of existing strokes (not just new ones), loop through the InkPresenter.StrokeContainer.GetStrokes() collection and update each stroke's DrawingAttributes.Opacity property individually.

内容的提问来源于stack exchange，提问作者Santhiya