以缩略图的形式从图库中转换图像（xamarin 形式）

Question

这是我在 pcl 项目 (ios/android)

中从图库中挑选图片的代码

        protected async Task PickImage()
    {
        try
        {
            Stream stream = await DependencyService.Get<IPicturePicker>().GetImageStreamAsync();

            {
                Image image = new Image
                {
                    Source = ImageSource.FromStream(() => stream),
                    BackgroundColor = Color.Gray
                };

                byte[] ImageData = Utils.Base64Utils.ToByteArray(stream);
                _base64String = Convert.ToBase64String(ImageData);

                editar_foto_perfil.Source = ImageSource.FromStream(() => new MemoryStream(Convert.FromBase64String(_base64String)));

                user.trocaImage = _base64String;

                if (Device.OS == TargetPlatform.iOS)
                {
                    user.cont_datanascimento = editar_date_datanasc.Date.ToString("yyyyMMdd");

                    if (editar_entry_nome.Text != null)
                        user.cont_nome = editar_entry_nome.Text;

                    if (editar_picker_estado.SelectedIndex != -1)
                        user.cont_estado = editar_picker_estado.Items[editar_picker_estado.SelectedIndex].ToString();

                    if (editar_picker_cidade.SelectedIndex != -1)
                        user.cont_cidade = editar_picker_cidade.Items[editar_picker_cidade.SelectedIndex].ToString();

                    if (editar_entry_senha.Text != null)
                        user.usua_senha = editar_entry_senha.Text;

                    if (editar_entry_email.Text != null)
                        user.usua_login = editar_entry_email.Text;

                    menu.RecriaEditarIOS(user);
                }
            }
        }
        catch (Exception ex)
        {
            var s = ex.Message;
        }
    }

有时我无法将选取的图像发送到服务器。通常，当图像很大时会发生这种情况，因此，我想将其调整为小图像并将其发送到服务器。有什么想法吗？

更新

我正在尝试我们的朋友在评论中建议的 Crossmedia 插件... 然后我改变了我的方法：

protected async Task PickImage()
    {
        try
        {
            //Stream stream = await DependencyService.Get<IPicturePicker>().GetImageStreamAsync();
            await CrossMedia.Current.Initialize();

            if (!CrossMedia.Current.IsPickPhotoSupported)
            {
                DisplayAlert("Photos Not Supported", ":( Permission not granted to photos.", "OK");
                return;
            }
            else
            {
            var file = await Plugin.Media.CrossMedia.Current.PickPhotoAsync(new Plugin.Media.Abstractions.PickMediaOptions
            {
                PhotoSize = Plugin.Media.Abstractions.PhotoSize.Medium,
            });             
        }
      }
        catch (Exception ex)
        {
            var s = ex.Message;
        }
    }

但是，文件始终为空

Answer 1

pick an image from the gallery in my PCL project and I want to resize it to a small image

您可以使用 MediaPlugin to implement this function, here is its simple usage:

pickPhoto.Clicked += async (sender, args) =>
{
    if (!CrossMedia.Current.IsPickPhotoSupported)
    {
      DisplayAlert("Photos Not Supported", ":( Permission not granted to photos.", "OK");
      return;
    }
     var file = await Plugin.Media.CrossMedia.Current.PickPhotoAsync(new Plugin.Media.Abstractions.PickMediaOptions
                  {
                      PhotoSize =  Plugin.Media.Abstractions.PhotoSize.Medium,
     });


    if (file == null)
      return;

    var stream = file.GetStream();
}

Class PickMediaOptions is used to resize the selected image, you could find the source code here.

更新：

这是我的代码，在我这边运行良好：

private async void button_Clicked(object sender, EventArgs e)
{
    await PickImage();
}

protected async Task PickImage()
{
    try
    {
        await CrossMedia.Current.Initialize();

        if (!CrossMedia.Current.IsPickPhotoSupported)
        {
            DisplayAlert("Photos Not Supported", ":( Permission not granted to photos.", "OK");
            return;
        }
        else
        {
            var file = await Plugin.Media.CrossMedia.Current.PickPhotoAsync(new Plugin.Media.Abstractions.PickMediaOptions
            {
                PhotoSize = Plugin.Media.Abstractions.PhotoSize.Medium,
            });

            if (file == null)
                return;

            image.Source = ImageSource.FromStream(() =>
            {
                var stream = file.GetStream();
                file.Dispose();
                return stream;
            });
        }
    }
    catch (Exception ex)
    {
        var s = ex.Message;
    }
}

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