使用FileSavePicker保存图像

本文介绍了使用FileSavePicker保存图像的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我有一个显示在图像控件中的图像，我需要使用FileSavePicker保存该图像

I have an image displayed in an Image Control and I need to save that Image using FileSavePicker

这就是我所做的:

Dim fileSavePicker As New FileSavePicker() fileSavePicker.FileTypeChoices.Add("PNG", New String() {".png"}) fileSavePicker.FileTypeChoices.Add("JPG", New String() {".jpg"}) fileSavePicker.FileTypeChoices.Add("BMP", New String() {".bmp"}) fileSavePicker.FileTypeChoices.Add("TIFF", New String() {".tiff"}) fileSavePicker.FileTypeChoices.Add("EXIF", New String() {".exif"}) fileSavePicker.FileTypeChoices.Add("ICO", New String() {".ico"}) Dim saveFile As StorageFile = Await fileSavePicker.PickSaveFileAsync() If saveFile IsNot Nothing Then //Here I need to save that Image End If

它正在保存图像，但带有"0 KB"，并显示空白图像.

It is saving the image but with "0 KB" and showing me the blank Image.

我该怎么办?

这是我得到的错误:

SaveToFile 不是Windows.UI.XAML.Media.Imaging.WriteableBitmap'的成员.

对于"加载"

这是我尝试加载图像的方式:

This is how I am trying to load image:

Private Async Sub Scenario1Button_Click(sender As Object, e As RoutedEventArgs) Handles Scenario1Button.Click Image1.Visibility = Windows.UI.Xaml.Visibility.Visible LayoutRoot.Visibility = Windows.UI.Xaml.Visibility.Collapsed grdImages.Visibility = Windows.UI.Xaml.Visibility.Collapsed Dim openPicker As New FileOpenPicker openPicker.ViewMode = PickerViewMode.List openPicker.SuggestedStartLocation = PickerLocationId.DocumentsLibrary openPicker.FileTypeFilter.Add("*") Dim files As IReadOnlyList(Of StorageFile) = Await openPicker.PickMultipleFilesAsync If files.Count > 0 Then 'Application now has read/write access to the picked file(s) For Each file In files Dim stream = Await file.OpenAsync(Windows.Storage.FileAccessMode.Read) Dim image As New BitmapImage() image.SetSource(stream) Image1.Source = image LayoutRoot.Visibility = Windows.UI.Xaml.Visibility.Collapsed Next file Else End If End Sub

推荐答案

根据文档:

对该方法的调用成功完成时，它将返回一个storageFile对象，该对象已创建以表示已保存的文件.该storageFile的文件名，扩展名和位置与用户指定的文件名，扩展名和位置匹配，但文件不包含任何内容. 要保存文件的内容，您的应用必须将内容写入此storageFile.

When the call to this method completes successfully, it returns a storageFile object that was created to represent the saved file. The file name, extension, and location of this storageFile match those specified by the user, but the file has no content. To save the content of the file, your app must write the content to this storageFile.

因此，您将获得一个存储文件，需要对其进行写入.

So you get a storage file and you need to write to it.

无法保存BitmapImage，因此您需要首先将图像加载到WriteableBitmap中.如果您只是复制原始文件，则可以将其加载到流中，然后将其保存回新的存储文件中.如果要使用WriteableBitmap路线-这是一组扩展方法，如果使用C#，则可以使用这些方法来加载/保存图像:

Saving a BitmapImage is not possible, so you would need to start off by loading the image into a WriteableBitmap. If you are just copying the original file - you can just load it to a stream and save it back to the new storage file. If you want to go the WriteableBitmap route - here is a set of extension methods you could use to load/save the image if you used C#:

using System; using System.Collections.Generic; using System.IO; using System.Linq; using System.Runtime.InteropServices.WindowsRuntime; using System.Text; using System.Threading.Tasks; using Windows.ApplicationModel; using Windows.Graphics.Imaging; using Windows.Storage; using Windows.Storage.Streams; using Windows.UI.Xaml.Media.Imaging; namespace Xyzzer.WinRT.Extensions { public static class WriteableBitmapSaveExtensions { public static async Task<WriteableBitmap> Load(string relativePath) { return await new WriteableBitmap(1, 1).Load(relativePath); } public static async Task<WriteableBitmap> Load(this WriteableBitmap writeableBitmap, string relativePath) { var storageFile = await Package.Current.InstalledLocation.GetFileAsync(relativePath.Replace('/', '\\')); return await writeableBitmap.Load(storageFile); } public static async Task<WriteableBitmap> Load(this WriteableBitmap writeableBitmap, StorageFile storageFile) { var stream = await storageFile.OpenReadAsync(); var wb = new WriteableBitmap(1, 1); wb.SetSource(stream); return wb; } public static async Task SaveToFile(this WriteableBitmap writeableBitmap) { await writeableBitmap.SaveToFile( KnownFolders.PicturesLibrary, string.Format( "{0}_{1}.png", DateTime.Now.ToString("yyyyMMdd_HHmmss_fff"), Guid.NewGuid())); } public static async Task SaveToFile(this WriteableBitmap writeableBitmap, StorageFolder storageFolder) { await writeableBitmap.SaveToFile( storageFolder, string.Format( "{0}_{1}.png", DateTime.Now.ToString("yyyyMMdd_HHmmss_fff"), Guid.NewGuid())); } public static async Task SaveToFile(this WriteableBitmap writeableBitmap, StorageFolder storageFolder, string fileName) { StorageFile outputFile = await storageFolder.CreateFileAsync(fileName, CreationCollisionOption.ReplaceExisting); Guid encoderId; var ext = Path.GetExtension(fileName); if (new[] { ".bmp", ".dib" }.Contains(ext)) { encoderId = BitmapEncoder.BmpEncoderId; } else if (new[] { ".tiff", ".tif" }.Contains(ext)) { encoderId = BitmapEncoder.TiffEncoderId; } else if (new[] { ".gif" }.Contains(ext)) { encoderId = BitmapEncoder.TiffEncoderId; } else if (new[] { ".jpg", ".jpeg", ".jpe", ".jfif", ".jif" }.Contains(ext)) { encoderId = BitmapEncoder.TiffEncoderId; } else if (new[] { ".hdp", ".jxr", ".wdp" }.Contains(ext)) { encoderId = BitmapEncoder.JpegXREncoderId; } else //if (new [] {".png"}.Contains(ext)) { encoderId = BitmapEncoder.PngEncoderId; } await writeableBitmap.SaveToFile(outputFile, encoderId); } public static async Task SaveToFile(this WriteableBitmap writeableBitmap, StorageFile outputFile, Guid encoderId) { try { Stream stream = writeableBitmap.PixelBuffer.AsStream(); byte[] pixels = new byte[(uint)stream.Length]; await stream.ReadAsync(pixels, 0, pixels.Length); int offset; for (int row = 0; row < (uint)writeableBitmap.PixelHeight; row++) { for (int col = 0; col < (uint)writeableBitmap.PixelWidth; col++) { offset = (row * (int)writeableBitmap.PixelWidth * 4) + (col * 4); byte B = pixels[offset]; byte G = pixels[offset + 1]; byte R = pixels[offset + 2]; byte A = pixels[offset + 3]; // convert to RGBA format for BitmapEncoder pixels[offset] = R; // Red pixels[offset + 1] = G; // Green pixels[offset + 2] = B; // Blue pixels[offset + 3] = A; // Alpha } } IRandomAccessStream writeStream = await outputFile.OpenAsync(FileAccessMode.ReadWrite); BitmapEncoder encoder = await BitmapEncoder.CreateAsync(encoderId, writeStream); encoder.SetPixelData(BitmapPixelFormat.Rgba8, BitmapAlphaMode.Premultiplied, (uint)writeableBitmap.PixelWidth, (uint)writeableBitmap.PixelHeight, 96, 96, pixels); await encoder.FlushAsync(); await writeStream.GetOutputStreamAt(0).FlushAsync(); } catch (Exception ex) { string s = ex.ToString(); } } } }