如何从WinForm pictureBox中的图像裁剪多边形区域？

Question

如何使用多边形裁剪图像的一部分？例如,我有6个坐标,我想剪切这部分图像.

Answer 1

您可以进行List的Points成多边形,然后进入一个GraphicsPath,然后进入Region后Graphics.Clip(Region),你可以Graphics.DrawImage和完成..:

using System.Drawing.Drawing2D;

GraphicsPath gp = new GraphicsPath();   // a Graphicspath
gp.AddPolygon(points.ToArray());        // with one Polygon

Bitmap bmp1 = new Bitmap(555,555);  // ..some new Bitmap
                                    // and some old one..:
using (Bitmap bmp0 = (Bitmap)Bitmap.FromFile("D:\\test_xxx.png"))
using (Graphics G = Graphics.FromImage(bmp1))
{
    G.Clip = new Region(gp);   // restrict drawing region
    G.DrawImage(bmp0, 0, 0);   // draw clipped
    pictureBox1.Image = bmp1;  // show maybe in a PictureBox
}
gp.Dispose();  

请注意,您可以随意选择DrawImage位置,包括位于原点左侧和顶部的负区域.

另请注意,对于"真实"裁剪,一些(至少4个)点数应该击中目标Bitmap的边界!- 或者您可以使用它GraphicsPath来获取其边界框:

RectangleF rect = gp.GetBounds();
Bitmap bmp1 = new Bitmap((int)Math.Round(rect.Width, 0), 
                         (int)Math.Round(rect.Height,0));
..