Windows 8学习笔记(十一)---图片的显示与保存

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<string> { ".jpg" });
StorageFile file = await fileSave.PickSaveFileAsync();</string>