裁剪图像并转换为PNG

Question

伙计我正在尝试裁剪图像并将其另存为PNG。

我可以剪裁得很好，但图片不能正确保存为PNG - 它会保存为JPEG格式或原始格式。 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();
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}

Answer 1

我对您的代码进行了一些更改。该方法返回表示为byte数组的整个PNG文件（不确定这是否是您要实现的目标）：

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]);
    byte[] rslt;

    Bitmap sourceImage;

    using (var fileStore = new EPMLiveFileStore(Web))
    {
        sourceImage = new Bitmap(fileStore.GetStream(FileNameField.Value));
    }

    using (var bitmap = new Bitmap(targetWidth, targetHeight))
    {
        bitmap.SetResolution(sourceImage.HorizontalResolution, sourceImage.VerticalResolution);

        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, targetWidth, targetHeight), new Rectangle(x, y, targetWidth, targetHeight), GraphicsUnit.Pixel);

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

由于您只是裁剪（不执行重新取样），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;

Answer 2

采用Jigstore和简化我认为你可以使用以下内容：

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，而JPEG中的缩略图仅举几例。如果您想保留此信息，我建议您通过命令行（http://www.hugsan.com/exifutils/）使用以下工具。