无法读取我刚刚保存在 Base64 中的位图图像

Question

我尝试加载图片(PNG(，将其保存在Base64的文本文件中并重新加载，但是从文本文件加载图片后，我只看到滑稽的图片(黑白，非常丑陋，远非原始！ 我的问题在哪里？

顺便说一句，所有示例(从图像文件加载图片，保存到base64，从base64加载(都取自SO问题。

首先是 如何从 PNG 文件加载图片：

try
{
var openFileDialog = new OpenFileDialog
{
CheckFileExists = true,
Multiselect = false,
DefaultExt = "png",
InitialDirectory =
Environment.GetFolderPath(Environment.SpecialFolder.MyPictures)
};
if (openFileDialog.ShowDialog() == true)
{
Bitmap img;
using (var stream = File.Open(openFileDialog.FileName, FileMode.Open, FileAccess.Read, FileShare.Read))
{
img = new Bitmap(stream);
}
Logo.Source = BitmapToImageSource(img);
}
}
catch (Exception exception)
{
MessageBox.Show(exception.ToString(), "An error occured", MessageBoxButton.OK, MessageBoxImage.Warning);
}

将其保存到base64：

try
{
Bitmap img = BitmapSourceToBitmap2((BitmapSource) Logo.Source);
string base64String;
using (var stream = new MemoryStream())
{
img.Save(stream, ImageFormat.Png);
byte[] imageBytes = stream.ToArray();
base64String = Convert.ToBase64String(imageBytes);
}
string fileName = string.Format(CultureInfo.InvariantCulture, "image{0:yyyyMMddHHmmss}.txt",
DateTime.Now);
string path = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), fileName);
using (var stream = File.Open(path, FileMode.CreateNew, FileAccess.Write, FileShare.None))
{
using (var writer = new StreamWriter(stream, System.Text.Encoding.UTF8))
{
writer.Write(base64String);
writer.Flush();
}
}
}
catch (Exception exception)
{
MessageBox.Show(exception.ToString(), "An error occured", MessageBoxButton.OK, MessageBoxImage.Warning);
}

位图源到位图2：

int width = srs.PixelWidth;
int height = srs.PixelHeight;
int stride = width*((srs.Format.BitsPerPixel + 7)/8);
IntPtr ptr = IntPtr.Zero;
try
{
ptr = Marshal.AllocHGlobal(height*stride);
srs.CopyPixels(new Int32Rect(0, 0, width, height), ptr, height*stride, stride);
using (var btm = new Bitmap(width, height, stride, PixelFormat.Format1bppIndexed, ptr))
{
// Clone the bitmap so that we can dispose it and
// release the unmanaged memory at ptr
return new Bitmap(btm);
}
}
finally
{
if (ptr != IntPtr.Zero)
Marshal.FreeHGlobal(ptr);
}

并将其从文件中加载回来：

try
{
var openFileDialog = new OpenFileDialog
{
CheckFileExists = true,
Multiselect = false,
DefaultExt = "txt",
InitialDirectory =
Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)
};
if (openFileDialog.ShowDialog() == true)
{
string base64String;
using (FileStream stream = File.Open(openFileDialog.FileName, FileMode.Open))
{
using (var reader = new StreamReader(stream))
{
base64String = reader.ReadToEnd();
}
}
byte[] binaryData = Convert.FromBase64String(base64String);
var bi = new BitmapImage();
bi.BeginInit();
bi.StreamSource = new MemoryStream(binaryData);
bi.EndInit();
Logo.Source = bi;
}
}
catch (Exception exception)
{
MessageBox.Show(exception.ToString(), "An error occured", MessageBoxButton.OK, MessageBoxImage.Warning);
}

Answer 1

这是一个简短的代码序列，它将 JPG 文件读入字节数组，从中创建 BitmapSource，然后将其编码为 base64 字符串并将其写入文件。

在第二步中，从文件中读回 base64 字符串，对其进行解码并创建第二个 BitmapSource。

此示例假定存在一些 XAML，其中包含名为image1和image2的两个图像元素。

第 1 步：

var imageFile = @"C:UsersClemensPicturesDSC06449.JPG";
var buffer = File.ReadAllBytes(imageFile);
using (var stream = new MemoryStream(buffer))
{
image1.Source = BitmapFrame.Create(
stream, BitmapCreateOptions.None, BitmapCacheOption.OnLoad);
}
var base64File = @"C:UsersClemensPicturesDSC06449.b64";
var base64String = System.Convert.ToBase64String(buffer);
File.WriteAllText(base64File, base64String);

第 2 步：

base64String = File.ReadAllText(base64File);
buffer = System.Convert.FromBase64String(base64String);
using (var stream = new MemoryStream(buffer))
{
image2.Source = BitmapFrame.Create(
stream, BitmapCreateOptions.None, BitmapCacheOption.OnLoad);
}

如果需要将现有的 BitmapSource 编码为字节数组，请使用如下代码：

var encoder = new PngBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create(bitmapSource));
using (var stream = new MemoryStream())
{
encoder.Save(stream);
buffer = stream.ToArray();
}