Metro style app 图片Scale ,Crop. 图片的打开,保存

Metro style app

一.图片Scale ,Crop操作

    public class PhotoEdit
    {
        public async static Task<WriteableBitmap> ScaleAndCorpPhoto(IStorageFile file)
        {
            if (file == null) return null;
            // create a stream from the file and decode the image
            var fileStream = await file.OpenAsync(Windows.Storage.FileAccessMode.Read);
            BitmapDecoder decoder = await BitmapDecoder.CreateAsync(fileStream);
            BitmapTransform transform = new BitmapTransform();
            BitmapBounds bounds = new BitmapBounds();
            transform.ScaledWidth = 500;
            transform.ScaledHeight = 500;
            const int croppedHeight = 400;
            const int croppedWidth = 400;
            bounds.Height = croppedHeight;
            bounds.Width = croppedWidth;
            bounds.X = 0;
            bounds.Y = 0;
            transform.Bounds = bounds;

            // Get the pixels in Bgra8 to match what the WriteableBitmap will expect
            PixelDataProvider pixelData = await decoder.GetPixelDataAsync(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Straight, transform, ExifOrientationMode.RespectExifOrientation, ColorManagementMode.ColorManageToSRgb);
            byte[] pixels = pixelData.DetachPixelData();

            // And stream them into a WriteableBitmap 
            WriteableBitmap cropBmp = new WriteableBitmap(croppedHeight, croppedWidth);
            Stream pixStream = cropBmp.PixelBuffer.AsStream();
            pixStream.Write(pixels, 0, pixels.Length);
            return cropBmp; 
        }
    }

 调用方法

        private async System.Threading.Tasks.Task ScaleAndCorpPhoto()
        { 
            FileOpenPicker fileOpenPicker = new FileOpenPicker();
            fileOpenPicker.CommitButtonText = "打开";
            fileOpenPicker.FileTypeFilter.Insert(0, ".jpg");
            StorageFile file = await fileOpenPicker.PickSingleFileAsync();
            if (file == null) return;
            image.Source = await PhotoEdit.ScaleAndCorpPhoto(file);
        }

 二、图片的打开与保存

1.图片的打开. 选择要显示的图片,最后将图片显示在Image控件中.

       private static BitmapImage srcImage = new BitmapImage();
        private static WriteableBitmap wbsrcImage;
        public async static void OpenImage(Image ImageOne)
        {
            FileOpenPicker imagePicker = new FileOpenPicker
            {
                ViewMode = PickerViewMode.Thumbnail,
                SuggestedStartLocation = PickerLocationId.PicturesLibrary,
                FileTypeFilter = { ".jpg", ".jpeg", ".png", ".bmp" }
            };

            Guid decoderId;
            StorageFile imageFile = await imagePicker.PickSingleFileAsync();
            if (imageFile != null)
            {
                srcImage = new BitmapImage();
                using (IRandomAccessStream stream = await imageFile.OpenAsync(FileAccessMode.Read))
                {
                    srcImage.SetSource(stream);
                    switch (imageFile.FileType.ToLower())
                    {
                        case ".jpg":
                        case ".jpeg":
                            decoderId = Windows.Graphics.Imaging.BitmapDecoder.JpegDecoderId;
                            break;
                        case ".bmp":
                            decoderId = Windows.Graphics.Imaging.BitmapDecoder.BmpDecoderId;
                            break;
                        case ".png":
                            decoderId = Windows.Graphics.Imaging.BitmapDecoder.PngDecoderId;
                            break;
                        default:
                            return;

                    }
                    Windows.Graphics.Imaging.BitmapDecoder decoder = await Windows.Graphics.Imaging.BitmapDecoder.CreateAsync(decoderId, stream);
                    int width = (int)decoder.PixelWidth;
                    int height = (int)decoder.PixelHeight;
                    Windows.Graphics.Imaging.PixelDataProvider dataprovider = await decoder.GetPixelDataAsync();
                    byte[] pixels = dataprovider.DetachPixelData();
                    wbsrcImage = new WriteableBitmap(width, height);
                    Stream pixelStream = wbsrcImage.PixelBuffer.AsStream();

                    //rgba in original   
                    //to display ,convert tobgra    
                    for (int i = 0; i < pixels.Length; i += 4)
                    {
                        byte temp = pixels[i];
                        pixels[i] = pixels[i + 2];
                        pixels[i + 2] = temp;
                    }
                    pixelStream.Write(pixels, 0, pixels.Length);
                    pixelStream.Dispose();
                    stream.Dispose();
                }

                ImageOne.Source = wbsrcImage;
                ImageOne.Width = wbsrcImage.PixelWidth;
                ImageOne.Height = wbsrcImage.PixelHeight;
            }

        }

 2.图片的保存. 将获得的WriteableBitmap保存起来. 比如你可以将Scale和Crop的图片保存起来.

        public async static Task SaveImage(WriteableBitmap src)
        {
            FileSavePicker save = new FileSavePicker();
            save.SuggestedStartLocation = PickerLocationId.PicturesLibrary;
            save.DefaultFileExtension = ".jpg";
            save.SuggestedFileName = "newimage";
            save.FileTypeChoices.Add(".bmp", new List<string>() { ".bmp" });
            save.FileTypeChoices.Add(".png", new List<string>() { ".png" });
            save.FileTypeChoices.Add(".jpg", new List<string>() { ".jpg", ".jpeg" });
            StorageFile savedItem = await save.PickSaveFileAsync();
            try
            {
                Guid encoderId;
                switch (savedItem.FileType.ToLower())
                {
                    case ".jpg":
                        encoderId = BitmapEncoder.JpegEncoderId;
                        break;
                    case ".bmp":
                        encoderId = BitmapEncoder.BmpEncoderId;
                        break;
                    case ".png":
                    default:
                        encoderId = BitmapEncoder.PngEncoderId;
                        break;

                }

                IRandomAccessStream fileStream = await savedItem.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite);
                BitmapEncoder encoder = await BitmapEncoder.CreateAsync(encoderId, fileStream);
                Stream pixelStream = src.PixelBuffer.AsStream();
                byte[] pixels = new byte[pixelStream.Length];
                pixelStream.Read(pixels, 0, pixels.Length);

                //pixal format shouldconvert to rgba8 
                for (int i = 0; i < pixels.Length; i += 4)
                {
                    byte temp = pixels[i];
                    pixels[i] = pixels[i + 2];
                    pixels[i + 2] = temp;
                }

                encoder.SetPixelData(
                  BitmapPixelFormat.Rgba8,
                  BitmapAlphaMode.Straight,
                  (uint)src.PixelWidth,
                  (uint)src.PixelHeight,
                  96, // Horizontal DPI 
                  96, // Vertical DPI 
                  pixels
                  );
                await encoder.FlushAsync();
            }
            catch (Exception e)
            {
                throw e;
            }
        }