在 C# 中，如何将 Base64 字符串转换为图像，然后旋转它？

Question

我在 Base64 中保存了横向和纵向混合的图像。 我想将它们全部显示为风景。

我能够将 Base64 字符串转换为 BitmapImages，然后将其设置为 Image.Source，但我无法使旋转工作。

在这个类中，我从 XML 获取 base64，然后调用 SetupImage，它设置 System.Windows.Controls.Image 对象的源。

我已经尝试了两种旋转图像的方法（当宽度小于高度时）都在这段代码中。 当我在 BitmapImage 上使用 Rotation 时，对显示的图像没有影响。 当我在图像上使用 RotateTransform 时，图像根本不显示。

public class TrayImage
{
    [XmlAttribute("id")]
    public string ID { get; set; }
    [XmlAttribute("data")]
    public string Data { get; set; }

    /// <summary>
    /// Create an Image from the Base64 Data
    /// </summary>
    internal void SetupImage(ref System.Windows.Controls.Image image)
    {
        if (this.Data != null)
        {
            // Convert the Base64 to a BitmapImage
            byte[] _BinaryData = Convert.FromBase64String(this.Data);

            BitmapImage _ImageBitmap = new BitmapImage();
            _ImageBitmap.BeginInit();
            _ImageBitmap.StreamSource = new MemoryStream(_BinaryData);
            _ImageBitmap.EndInit();

            // If the image is portrait, rotate it
            if (_ImageBitmap.Width < _ImageBitmap.Height)
            {
                // only use one rotation method at a time!!
                //_ImageBitmap.Rotation = Rotation.Rotate90;
            }

            image.Source = _ImageBitmap;

            // If the image is portrait, rotate it
            if( image.Source.Width < image.Source.Height)
            {
                // only use one rotation method at a time!!
                RotateTransform _RotateTransform = new RotateTransform(90);
                image.RenderTransform = _RotateTransform;
            }
        }
    }
}

我应该使用其他东西来转换，然后旋转图像吗？

Answer 1

像这样：这只是为了说明代码未测试！

public static class ImageHelpers
{
    punlic byte[] ConvertFromBase64(btye[] data)
    {
        return Convert.FromBase64String(data)
    }

    public  Image Rotate90FromData(byte[] data)
    {
        Image image = null;
        if (data != null)
        {             
            BitmapImage _ImageBitmap = new BitmapImage();
            _ImageBitmap.BeginInit();
            _ImageBitmap.StreamSource = new MemoryStream(data);
            _ImageBitmap.EndInit();

            image.Source = _ImageBitmap;

            // If the image is portrait, rotate it
            if( image.Source.Width < image.Source.Height)
            {
                RotateTransform _RotateTransform = new RotateTransform(90);
                image.RenderTransform = _RotateTransform;
            }
        }
        return Image;
    }
}

public class Main
{
    public void Start()
    {
        var data64 = ImageHelpers.ConvertFromBase64(somevar);
        Image rotatedImage = ImageHelpers.Rotate90FromData(data64);

    }
}

Answer 2

在梳理了这里的建议以及其他问题后，我想出了一个可行的解决方案。

这些是我的“用途”

using System;
using System.Xml.Serialization;
using System.IO;
using System.Windows.Media.Imaging;
using System.Drawing;

这是我的全班

public class TrayImage
{
    [XmlAttribute("id")]
    public string ID { get; set; }
    [XmlAttribute("data")]
    public string Data { get; set; }

    /// <summary>
    /// Create an Image from the Base64 Data
    /// </summary>
    internal System.Windows.Controls.Image SetupImage()
    {
        System.Windows.Controls.Image _Image = new System.Windows.Controls.Image();

        if (this.Data != null)
        {
            BitmapImage _BitmapImage = this.CreateBitmapImage();
            Bitmap _Bitmap = this.BitmapImage2Bitmap(_BitmapImage);

            // If the image is portrait, rotate it
            if (_Bitmap.Width < _Bitmap.Height)
            {
                _Bitmap = this.RotateImage(_Bitmap, 90);
            }

            _Image.Source = this.BitmapToBitmapImage(_Bitmap);
        }

        return _Image;
    }

    /// <summary>
    /// Convert a Bitmap into a BitmapImage
    /// </summary>
    private BitmapImage BitmapToBitmapImage(Bitmap bitmap)
    {
        using (MemoryStream _MemoryStream = new MemoryStream())
        {
            bitmap.Save(_MemoryStream, System.Drawing.Imaging.ImageFormat.Bmp);
            _MemoryStream.Position = 0;
            BitmapImage _BitmapImage = new BitmapImage();
            _BitmapImage.BeginInit();
            _BitmapImage.StreamSource = _MemoryStream;
            _BitmapImage.CacheOption = BitmapCacheOption.OnLoad;
            _BitmapImage.EndInit();

            return _BitmapImage;
        }
    }

    /// <summary>
    /// Convert a Base64 String into a BitmapImage
    /// </summary>
    private BitmapImage CreateBitmapImage()
    {
        byte[] _BinaryData = Convert.FromBase64String(this.Data);

        BitmapImage _ImageBitmap = new BitmapImage();
        _ImageBitmap.BeginInit();
        _ImageBitmap.StreamSource = new MemoryStream(_BinaryData);
        _ImageBitmap.EndInit();

        return _ImageBitmap;
    }

    /// <summary>
    /// Convert a BitmapImage into a Bitmap
    /// </summary>
    private Bitmap BitmapImage2Bitmap(BitmapImage bitmapImage)
    {
        using (MemoryStream _OutStream = new MemoryStream())
        {
            BitmapEncoder _Encoder = new BmpBitmapEncoder();
            _Encoder.Frames.Add(BitmapFrame.Create(bitmapImage));
            _Encoder.Save(_OutStream);
            System.Drawing.Bitmap _Bitmap = new System.Drawing.Bitmap(_OutStream);

            return new Bitmap(_Bitmap);
        }
    }

    /// <summary>
    /// Rotate a Bitmap
    /// </summary
    private Bitmap RotateImage(Bitmap bitmap, float angle)
    {
        int _Width = bitmap.Width;
        int _Height = bitmap.Height;
        float _MoveX = (float)_Height / 2;

        // Create bitmap with Height / Width revered
        Bitmap _ReturnBitmap = new Bitmap(_Height, _Width);

        // Make a graphics object from the empty bitmap
        using (Graphics _Graphics = Graphics.FromImage(_ReturnBitmap))
        {
            // Move image along x axis
            _Graphics.TranslateTransform(_MoveX, 0);

            // Rotate image
            _Graphics.RotateTransform(angle);

            // Move image back along x axis
            // NB, now it's been rotated, the x and y axis have swapped from our perspective.
            _Graphics.TranslateTransform(0, -_MoveX);

            // Draw passed in image onto graphics object
            _Graphics.DrawImage(bitmap, new Point(0, 0));
        }
        return _ReturnBitmap;
    }
}

Answer 3

我是这样做的：

using System.IO;    
using System.Drawing;

public Bitmap RotateBase64Image(string base64Image)
{
     Bitmap result = null;
     try
     {
          if (!string.IsNullOrEmpty(base64Image))
          {
              //Check if base64 string has a header
              if (base64Image.IndexOf("base64") >= 0 && base64Image.IndexOf(",") > 0)
              {
                  //get image data and exclude header
                  base64Image = base64Image.Split(',')[1];
              }
              using (MemoryStream ms = new MemoryStream(Convert.FromBase64String(base64Image)))
              {
                  using (Bitmap bitmap = new Bitmap(ms))
                  {
                      //rotate 90 degree clockwise with no flip
                      bitmap.RotateFlip(RotateFlipType.Rotate90FlipNone);
                      //rotate 180 degree clockwise with no flip
                      bitmap.RotateFlip(RotateFlipType.Rotate180FlipNone);
                      //rotate 270 degree clockwise with no flip
                      bitmap.RotateFlip(RotateFlipType.Rotate270FlipNone);
                      //Flip Image horizontally with out any rotation
                      bitmap.RotateFlip(RotateFlipType.RotateNoneFlipX);
                      //Flip Image vertically with out any rotation
                      bitmap.RotateFlip(RotateFlipType.RotateNoneFlipY);

                      result = (Bitmap)bitmap.Clone();                            
                }
            }
        }
    }
    catch { }

    return result;
}

而且，如果您再次需要结果为 base64：

public string ConvertBitmapToBase64(Bitmap image)
{
    string result = "";
    try
    {
        using (MemoryStream ms2 = new MemoryStream())
        {
            image.Save(ms2, System.Drawing.Imaging.ImageFormat.Png);
            return Convert.ToBase64String(ms2.ToArray());

            //If you need the result with header
            //return "data:image/png;base64," + Convert.ToBase64String(ms2.ToArray());
        }
    }
    catch { }

    return result;
}