使用Graphics绘制图像

使用Graphics绘制图像

使用Aspose.PSD库，您可以绘制简单的形状，如直线、矩形和圆，以及复杂的形状，如多边形、曲线、弧形和贝塞尔形状。Aspose.PSD库使用位于Aspose.PSD命名空间中的Graphics类创建这些形状。Graphics对象负责在图像上执行不同的绘图操作，从而改变图像的表面。Graphics类使用各种辅助对象来增强形状：

·         画笔，用于绘制线条、轮廓形状或呈现其他几何表示。

·         笔刷，定义填充区域的方式。

·         字体，定义文本的字符形状。

使用Graphics类绘图

以下是演示使用Graphics类的代码示例。示例源代码已分成几个部分，以保持简单易懂。逐步介绍了如何：

1. 创建图像。
2. 创建并初始化Graphics对象。
3. 清除表面。
4. 绘制椭圆。
5. 绘制填充多边形并保存图像。

编程示例

创建图像

首先使用Creating Files中描述的任何方法创建图像。

// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

string loadpath = dataDir + "sample.psd";
string outpath = dataDir + "CoreDrawingFeatures.bmp";
// Create an instance of Image
using (PsdImage image = new PsdImage(loadpath))
{
    // load pixels
    var pixels = image.LoadArgb32Pixels(new Rectangle(0, 0, 100, 10));

    for (int i = 0; i < pixels.Length; i++)
    {
        // specify pixel color value (gradient in this case).
        pixels[i] = i;
    }

    // save modified pixels.
    image.SaveArgb32Pixels(new Rectangle(0, 0, 100, 10), pixels);

    // export image to bmp file format.
    image.Save(outpath, new BmpOptions());
}

创建并初始化Graphics对象

然后通过将Image对象传递给其构造函数来创建和初始化Graphics对象。

// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

string outpath = dataDir + "Arc.bmp";
// Create an instance of BmpOptions and set its various properties
BmpOptions saveOptions = new BmpOptions();
saveOptions.BitsPerPixel = 32;

// Create an instance of Image
using (Image image = new PsdImage(100, 100))
{
    // Create and initialize an instance of Graphics class and clear Graphics surface
    Graphics graphic = new Graphics(image);
    graphic.Clear(Color.Yellow);

    // Draw an arc shape by specifying the Pen object having red black color and coordinates, height, width, start & end angles                 
    int width = 100;
    int height = 200;
    int startAngle = 45;
    int sweepAngle = 270;

    // Draw arc to screen and save all changes.
    graphic.DrawArc(new Pen(Color.Black), 0, 0, width, height, startAngle, sweepAngle);

    // export image to bmp file format.
    image.Save(outpath, saveOptions);
}

清除表面

通过调用Graphics类的Clear方法并将颜色作为参数传递来清除Graphics表面。该方法将Graphics表面用传递的颜色填充。

// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

// Create an instance of Image
using (PsdImage image = new PsdImage(500, 500))
{
    var graphics = new Graphics(image);

    // Clear the image surface with white color and Create and initialize a Pen object with blue color
    graphics.Clear(Color.White);
    var pen = new Pen(Color.Blue);

    // Draw Ellipse by defining the bounding rectangle of width 150 and height 100 also Draw a polygon using the LinearGradientBrush
    graphics.DrawEllipse(pen, new Rectangle(10, 10, 150, 100));
    using (var linearGradientBrush = new LinearGradientBrush(image.Bounds, Color.Red, Color.White, 45f))
    {
        graphics.FillPolygon(linearGradientBrush, new[] { new Point(200, 200), new Point(400, 200), new Point(250, 350) });
    }

    // export modified image.
    image.Save(dataDir + "DrawingUsingGraphics_output.bmp", new BmpOptions());
}

绘制椭圆

您可能注意到Graphics类公开了许多绘制和填充形状的方法。您可以在Aspose.PSD for .NET API参考中找到这些方法的完整列表。Graphics类公开了几个重载版本的DrawEllipse方法。所有这些方法都接受Pen对象作为第一个参数。将后续参数传递以定义围绕椭圆的矩形。为了本示例，使用接受Rectangle对象作为第二参数的版本，使用所需颜色的Pen对象绘制椭圆。

// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

string loadpath = dataDir + "sample.psd";
string outpath = dataDir + "CoreDrawingFeatures.bmp";
// Create an instance of Image
using (PsdImage image = new PsdImage(loadpath))
{
    // load pixels
    var pixels = image.LoadArgb32Pixels(new Rectangle(0, 0, 100, 10));

    for (int i = 0; i < pixels.Length; i++)
    {
        // specify pixel color value (gradient in this case).
        pixels[i] = i;
    }

    // save modified pixels.
    image.SaveArgb32Pixels(new Rectangle(0, 0, 100, 10), pixels);

    // export image to bmp file format.
    image.Save(outpath, new BmpOptions());
}

绘制填充多边形

接下来，使用LinearGradientBrush和一系列点绘制多边形。Graphics类公开了多个重载版本的FillPolygon()方法。所有这些方法都接受Brush对象作为第一个参数，定义填充的特性。第二个参数是一系列点。请注意，数组中每两个连续的点指定多边形的一条边。

// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

// Create an instance of Image
using (PsdImage image = new PsdImage(500, 500))
{
    var graphics = new Graphics(image);

    // Clear the image surface with white color and Create and initialize a Pen object with blue color
    graphics.Clear(Color.White);
    var pen = new Pen(Color.Blue);

    // Draw Ellipse by defining the bounding rectangle of width 150 and height 100 also Draw a polygon using the LinearGradientBrush
    graphics.DrawEllipse(pen, new Rectangle(10, 10, 150, 100));
    using (var linearGradientBrush = new LinearGradientBrush(image.Bounds, Color.Red, Color.White, 45f))
    {
        graphics.FillPolygon(linearGradientBrush, new[] { new Point(200, 200), new Point(400, 200), new Point(250, 350) });
    }

    // export modified image.
    image.Save(dataDir + "DrawingUsingGraphics_output.bmp", new BmpOptions());
}

使用Graphics绘制图像：完整源码

// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

// Create an instance of Image
using (PsdImage image = new PsdImage(500, 500))
{
    var graphics = new Graphics(image);

    // Clear the image surface with white color and Create and initialize a Pen object with blue color
    graphics.Clear(Color.White);
    var pen = new Pen(Color.Blue);

    // Draw Ellipse by defining the bounding rectangle of width 150 and height 100 also Draw a polygon using the LinearGradientBrush
    graphics.DrawEllipse(pen, new Rectangle(10, 10, 150, 100));
    using (var linearGradientBrush = new LinearGradientBrush(image.Bounds, Color.Red, Color.White, 45f))
    {
        graphics.FillPolygon(linearGradientBrush, new[] { new Point(200, 200), new Point(400, 200), new Point(250, 350) });
    }

    // export modified image.
    image.Save(dataDir + "DrawingUsingGraphics_output.bmp", new BmpOptions());
}

所有实现IDisposable并访问非托管资源的类都通过Using语句进行实例化，以确保其正确释放。