Windows 8学习笔记(十一)---图片的显示与保存

lanying56123

　　图片显示
　　图片的显示应该都非常熟悉，场景很多，我先把我想的三个列举一下：
　　场景一：
　　从本地图片库选择图片进行显示：
async private void LoadPictureByPicker()
{
FileOpenPicker fileOpen = new FileOpenPicker()
{
FileTypeFilter={ ".jpg", ".jpeg", ".png", ".bmp" },
ViewMode=PickerViewMode.Thumbnail,
SuggestedStartLocation=PickerLocationId.PicturesLibrary
};
bitmapImage = new BitmapImage();
storageFile = await fileOpen.PickSingleFileAsync();
if (storageFile != null)
{
using (IRandomAccessStream stream = await storageFile.OpenAsync(FileAccessMode.Read))
{
bitmapImage.SetSource(stream);
}
}
img.Source = bitmapImage;
}　　

　　场景二：
　　直接请求网络URL
　　string url = "http://ww4.sinaimg.cn/bmiddle/8193c63ajw1ds3o5e56jaj.jpg";
　　方法一：

BitmapImage bitmapImage = new BitmapImage(new Uri(url));
img.Source = bitmapImage;
　　方法二：

async private void LoadPictrueByUrl()
{
var  rass = RandomAccessStreamReference.CreateFromUri(new Uri(url));
streamRandom = await rass.OpenReadAsync();
var bitmapImage = new BitmapImage();
bitmapImage.SetSource(streamRandom);
img.Source = bitmapImage;
}
　　若是简单的显示图片，用方法一就足够了，若需要保存图片，还是用方法二，因为方法一我目前还没有办法截取到它的流，除非再用HttpRequest请求一次;用方法二相对而言，就方便多了。
　　
　　场景三：
　　显示项目文件中的图片
　　string url = "ms-appx:///images/flower.jpg";
　　方法一：

BitmapImage bitmapImage = new BitmapImage(new Uri(url));
img.Source = bitmapImage;
　　方法二：

async private void LoadPictureByNative()
{
var  rass = RandomAccessStreamReference.CreateFromUri(new Uri(url));
streamRandom = await rass.OpenReadAsync();
var bitmapImage = new BitmapImage();
bitmapImage.SetSource(streamRandom);
img.Source = bitmapImage;
}
　　原理与场景二是类似的
　　
　　保存图片
　　保存图片也分两种情况
　　直接保存到图片库

StorageFolder folder = KnownFolders.PicturesLibrary;
storageFile = await folder.CreateFileAsync("sample.jpg", CreationCollisionOption.ReplaceExisting);
IBuffer buffer = RandomAccessStreamToBuffer(streamRandom);
await FileIO.WriteBufferAsync(storageFile, buffer);　　RandomAccessStreamToBuffer是自定的转换方法,在前面流的转换中也已写了,这里再写一下吧..


private IBuffer RandomAccessStreamToBuffer(IRandomAccessStream randomstream)
{
Stream stream = WindowsRuntimeStreamExtensions.AsStreamForRead(randomstream.GetInputStreamAt(0));
MemoryStream memoryStream = new MemoryStream();
if (stream != null)
{
byte[] bytes = ConvertStreamTobyte(stream);
if (bytes != null)
{
var binaryWriter = new BinaryWriter(memoryStream);
binaryWriter.Write(bytes);
}
}
IBuffer buffer = WindowsRuntimeBufferExtensions.GetWindowsRuntimeBuffer(memoryStream, 0, (int)memoryStream.Length);
return buffer;
}

public static byte[] ConvertStreamTobyte(Stream input)
{
byte[] buffer = new byte[16 * 1024];
using (MemoryStream ms = new MemoryStream())
{
int read;
while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
{
ms.Write(buffer, 0, read);
}
return ms.ToArray();
}
}　　

　　显示保存文件对话框，可以自行选择保存路径，这时需用到FileSavePicker

FileSavePicker fileSave = new FileSavePicker();
fileSave.SuggestedSaveFile = storageFile;
fileSave.SuggestedStartLocation = PickerLocationId.Desktop;
fileSave.SuggestedFileName = "test418";
fileSave.DefaultFileExtension = ".jpg";
fileSave.FileTypeChoices.Add("JPEG file", new List { ".jpg" });
StorageFile file = await fileSave.PickSaveFileAsync();　　
　　可能我上面的方法不是很简单方便，希望有更简捷的同胞可以共同分享下哈~