C# 裁剪图像并转换为PNG

伙计们，我正在尝试裁剪图像并将其保存为PNG

我可以很好地裁剪它，但是图像没有正确地保存为PNG——它被保存为JPEG或任何原始格式仅当用户决定不裁剪图像时。

这就是我的意思，即使我设置了

ImageFormat.Png

图像也会保存为JPEG

以下是我正在使用的代码：

private byte[] ResizeImage2(string resizeInfo)
{
    string[] picInfo = resizeInfo.Split('|');

    int width = int.Parse(picInfo[0]);
    int height = int.Parse(picInfo[1]);
    int targetWidth = int.Parse(picInfo[2]);
    int targetHeight = int.Parse(picInfo[3]);
    int x = int.Parse(picInfo[4]);
    int y = int.Parse(picInfo[5]);

    using (var fileStore = new EPMLiveFileStore(Web))
    {
        using (var sourceImage = new Bitmap(fileStore.GetStream(FileNameField.Value)))
        {
            using (var bitmap = new Bitmap(width, height))
            {
                using (var graphics = Graphics.FromImage(bitmap))
                {
                    graphics.CompositingQuality = CompositingQuality.HighQuality;
                    graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
                    graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;
                    graphics.SmoothingMode = SmoothingMode.HighQuality;

                    graphics.DrawImage(sourceImage, new Rectangle(0, 0, width, height));

                    using (var memoryStream = new MemoryStream())
                    {
                        bitmap.Save(memoryStream, ImageFormat.Png);

                        using (var bmp = new Bitmap(bitmap))
                        {
                            using (var pic = bmp.Clone(new Rectangle(x, y, targetWidth, targetHeight), bitmap.PixelFormat))
                            {
                                using (var stream = new MemoryStream())
                                {
                                    pic.Save(stream, ImageFormat.Png);
                                    return stream.ToArray();
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}

---

我对你的代码做了一些更改。该方法返回整个PNG文件，表示为

字节

数组（不确定这是否是您想要实现的）：

由于只进行裁剪（不执行重采样），因此可能不需要以下行：

graphics.CompositingQuality = CompositingQuality.HighQuality;
graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;
graphics.SmoothingMode = SmoothingMode.HighQuality;

---

以Jigstore和Simplify为例，我认为您可以使用以下方法：

private byte[] ResizeImage2(string resizeInfo)
{
  string[] picInfo = resizeInfo.Split('|');
  int width = int.Parse(picInfo[0]);
  int height = int.Parse(picInfo[1]);
  int targetWidth = int.Parse(picInfo[2]);
  int targetHeight = int.Parse(picInfo[3]);
  int x = int.Parse(picInfo[4]);
  int y = int.Parse(picInfo[5]);

  using (var fileStore = new EPMLiveFileStore(Web))
  {
    using (Bitmap sourceImage = new Bitmap(fileStore.GetStream(FileNameField.Value)))
    {
      using (var bitmap = new Bitmap(width, height))
      {
        bitmap.SetResolution(sourceImage.HorizontalResolution, sourceImage.VerticalResolution);

        using (var graphics = Graphics.FromImage(bitmap))
        {
          graphics.DrawImageUnscaled(sourceImage, Point.Empty);

          using (var memoryStream = new MemoryStream())
          {
              bitmap.Save(memoryStream, ImageFormat.Png);
              return (byte[]) memoryStream.ToArray();
          }
        }
      }
    }
  }
}

---

顺便说一下，您将丢失原始文件中的所有元数据。这将是EXIF信息和JPEG中的缩略图，仅举几个例子。如果您想保留此信息，我建议您通过命令行（）使用如下工具。

您是否尝试过另一个采用ImageFormat参数的Bitmap.Save（）方法重载？我添加了屏幕截图。它对我来说很好（即使我“裁剪”整个图像，实际上没有裁剪），文件保存为PNG，我用十六进制编辑器检查了一下。顺便说一句，您的版本似乎没有保留DPI设置。如果你上传的图像可能与MIME类型有关。

private byte[] ResizeImage2(string resizeInfo)
{
  string[] picInfo = resizeInfo.Split('|');
  int width = int.Parse(picInfo[0]);
  int height = int.Parse(picInfo[1]);
  int targetWidth = int.Parse(picInfo[2]);
  int targetHeight = int.Parse(picInfo[3]);
  int x = int.Parse(picInfo[4]);
  int y = int.Parse(picInfo[5]);

  using (var fileStore = new EPMLiveFileStore(Web))
  {
    using (Bitmap sourceImage = new Bitmap(fileStore.GetStream(FileNameField.Value)))
    {
      using (var bitmap = new Bitmap(width, height))
      {
        bitmap.SetResolution(sourceImage.HorizontalResolution, sourceImage.VerticalResolution);

        using (var graphics = Graphics.FromImage(bitmap))
        {
          graphics.DrawImageUnscaled(sourceImage, Point.Empty);

          using (var memoryStream = new MemoryStream())
          {
              bitmap.Save(memoryStream, ImageFormat.Png);
              return (byte[]) memoryStream.ToArray();
          }
        }
      }
    }
  }
}