读取同一图像流两次

Question

我想获取图像的尺寸并在同一时间或之后将图像流式传输到对象。像这样的代码。

string page = pages[pageComboBox.SelectedIndex].pageImage;          // image url
var stream = web.OpenRead(page);
var bitmap = new BitmapImage();
bitmap.BeginInit();
bitmap.StreamSource = stream;                // First read stream 
stream.Position = 0;                         // tried
bitmap.CacheOption = BitmapCacheOption.OnLoad;
bitmap.EndInit();
pageIMG.Source = bitmap;
Image image = Image.FromStream(stream);      // Second read stream
MessageBox.Show("Image Height = " + image.Height + " Image Width = " + image.Width);

我确实使用了位置的东西，但它给了我一个错误 -

'This stream does not support seek operations.'

请帮忙...

Answer 1

将源流复制到 MemoryStream：

using (var memoryStream = new MemoryStream())
{
    stream.CopyTo(memoryStream);

    memoryStream.Position = 0;
    bitmap.BeginInit();
    bitmap.StreamSource = memoryStream;
    bitmap.CacheOption = BitmapCacheOption.OnLoad;
    bitmap.EndInit();
    ...

    memoryStream.Position = 0;
    image = Image.FromStream(memoryStream);
    ...
}

但是，将流再次读入 WinForms Image 似乎毫无意义。您可以只查询 BitmapImage 的 PixelWidth 和 PixelHeight 属性：

using (var memoryStream = new MemoryStream())
{
    stream.CopyTo(memoryStream);

    memoryStream.Position = 0;
    bitmap.BeginInit();
    bitmap.StreamSource = memoryStream;
    bitmap.CacheOption = BitmapCacheOption.OnLoad;
    bitmap.EndInit();
    ...

    MessageBox.Show(
        "Image Height = " + bitmap.PixelHeight +
        " Image Width = " + bitmap.PixelWidth);
}

读取同一图像流两次

Reading the Same Image Stream Twice

c#

wpf

image

stream