裁剪 Graphics 对象？

Question

我需要对图像做两件事：调整其大小，然后裁剪它。

我像这样调整大小：

nonResizedImage = new Bitmap(imagePath);
Bitmap scaled = new Bitmap(preCropWidth, preCropHeight);
using (Graphics scaledGraphics = Graphics.FromImage(scaled)) 
{ // scale image to the sizeo f the image the user cropped on
    scaledGraphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
    scaledGraphics.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighSpeed;
    scaledGraphics.CompositingMode = System.Drawing.Drawing2D.CompositingMode.SourceCopy;
    scaledGraphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
    scaledGraphics.Clear(ColorTranslator.FromHtml("#FFFFFF"));
    scaledGraphics.DrawImage(nonResizedImage, 0, 0, preCropWidth, preCropHeight);
}

现在我需要裁剪图像。我找到了一个可以执行此操作的函数：

static byte[] Crop(string Img, int Width, int Height, int X, int Y)
{
    try
    {
        using (SD.Image OriginalImage = SD.Image.FromFile(Img))
        {
            using (SD.Bitmap bmp = new SD.Bitmap(Width, Height))
            {
                bmp.SetResolution(OriginalImage.HorizontalResolution, OriginalImage.VerticalResolution);

                using (SD.Graphics Graphic = SD.Graphics.FromImage(bmp))
                {
                    Graphic.SmoothingMode = SmoothingMode.AntiAlias;
                    Graphic.InterpolationMode = InterpolationMode.HighQualityBicubic;
                    Graphic.PixelOffsetMode = PixelOffsetMode.HighQuality;
                    Graphic.DrawImage(OriginalImage, new SD.Rectangle(0, 0, Width, Height), X, Y, Width, Height, SD.GraphicsUnit.Pixel);
                    MemoryStream ms = new MemoryStream();
                    bmp.Save(ms, OriginalImage.RawFormat);
                    return ms.GetBuffer();
                }
            }
        }
    }

    catch (Exception Ex)
    {
        throw Ex;
    }
}

但这需要图像作为输入。因此，我可以将调整大小代码的输出保存到磁盘，然后再次读回以进行裁剪，但这似乎效率低下。不过，我对 C# 中的图像处理不太了解。

如何裁剪我拥有的 scaledGraphics，而不先将其保存到磁盘？

Answer 1

新位图的重载之一是宽度、高度、图形对象。您应该能够只传递图形对象，然后从中创建位图。像这样的东西

  static byte[] Crop(Graphics g, int Width, int Height, int X, int Y)
  {
      try
       {
          using (Bitmap bmp = new Bitmap(Width, Height, g))
          { 
           ...
          }
        }
        ......
    }