UWP 图片分割，剪切 WriteableBitmap 操作

 //WriteableBitmap 转 颜色数组

        public static Color[,] ArraytoBitmap(WriteableBitmap writeableBitmap)

        {

            //《图转化成流》

            /////////////////////////////////////////////////////////////////////////////

            int width = writeableBitmap.PixelWidth; //获取宽度

            int height = writeableBitmap.PixelHeight;//获取高度

            Stream stream = writeableBitmap.PixelBuffer.AsStream();//Bitmap=>Stream

            byte[] buffer = new byte[stream.Length]; //创建新Buffer，长度是Stream的长度

            stream.Read(buffer, 0, buffer.Length); //Stream.Read写入，由Buffer引用（从零到其长度）

            //《流转化成组》

            /////////////////////////////////////////////////////////////////////////////

            Color[,] color = new Color[height, width]; //声明颜色二维数组，用来存储图片

            for (int y = 0; y < height; y++)

            {

                for (int x = 0; x < width; x++)

                {

                    int Num = (y * width + x) * 4;//计算第一个点的位置

                    color[y, x] = Color.FromArgb(buffer[Num + 3], buffer[Num + 2], buffer[Num + 1], buffer[Num]);//改变颜色，buffer=>color[,]

                }

            }

            return color; //返回颜色二维数组

        }

 

//颜色数组转WriteableBitmap：

        public static WriteableBitmap BitmaptoArray(Color[,] color)

        {

            //《组转化成流》

            //////////////////////////////////////////////////////////////////////////////////////////////////

            int height = color.GetLength(0); //获取二维数组的2    { 1,1,1,1,1 }

            int width = color.GetLength(1); //获取二维数组的5     { 1,1,1,1,1 }

            Byte[] buffer = new Byte[color.Length * 4]; //创建流，长度是数组长度的4倍，存储BGRA四个分量

            for (int y = 0; y < height; y++)

            {

                for (int x = 0; x < width; x++)

                {

                    Color cooo = color[y, x]; //临时颜色

                    int Num = (y * width + x) * 4;//计算第一个点的位置

                    buffer[Num] = cooo.B;//蓝色B

                    buffer[Num + 1] = cooo.G;//绿色G

                    buffer[Num + 2] = cooo.R;//红色R

                    buffer[Num + 3] = cooo.A;//透明度Alpha

                }

            }

            //《流转化成图》

            //////////////////////////////////////////////////////////////////////////////////////////////////

            WriteableBitmap writeableBitmap = new WriteableBitmap(width, height);//创建新Bitmap，宽高是图片宽高

            Stream stream = writeableBitmap.PixelBuffer.AsStream(); //Bitmap=>Stream

            stream.Seek(0, SeekOrigin.Begin);//Stream.Seek寻找（从零开始）

            stream.Write(buffer, 0, buffer.Length);//Stream.Write写入，写入Buffer（从零到其长度）

            return writeableBitmap;

        }

 

 待测试。。。。。。

 

 

 下面这最有效：

 public async void BitmapTransformAndSaveTest()
        {
            var uncroppedfile = await Windows.Storage.ApplicationData.Current.LocalFolder.GetFileAsync("uncropped.jpg");
            if (uncroppedfile == null)
            {
                return;
            }

            WriteableBitmap wb = null;

            // create a stream from the file and decode the image
            var fileStream = await uncroppedfile.OpenAsync(Windows.Storage.FileAccessMode.Read);
            var decoder = await BitmapDecoder.CreateAsync(fileStream);

            // create a new stream and encoder for the new image
            using (InMemoryRandomAccessStream ras = new InMemoryRandomAccessStream())
            {
                var enc = await BitmapEncoder.CreateForTranscodingAsync(ras, decoder);

                // convert the entire bitmap to a 100px by 100px bitmap
                enc.BitmapTransform.ScaledHeight = 100;
                enc.BitmapTransform.ScaledWidth = 100;

                var bounds = new BitmapBounds();
                bounds.Height = 50;
                bounds.Width = 50;
                bounds.X = 50;
                bounds.Y = 50;
                enc.BitmapTransform.Bounds = bounds;

                // write out to the stream
                await enc.FlushAsync();

                // create a writeable bitmap from the stream
                ras.Seek(0);
                wb = new WriteableBitmap(100, 100);
                wb.SetSource(ras);
            }

            // save the cropped file now
            var croppedfile = await Windows.Storage.ApplicationData.Current.LocalFolder.CreateFileAsync("cropped.jpg", Windows.Storage.CreationCollisionOption.ReplaceExisting);
            using (var stream = await croppedfile.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite))
            {
                var pixelStream = wb.PixelBuffer.AsStream();
                var bytes = new byte[pixelStream.Length];
                pixelStream.Seek(0, SeekOrigin.Begin);
                await pixelStream.ReadAsync(bytes, 0, (int)pixelStream.Length);
                await pixelStream.FlushAsync();

                var encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.JpegEncoderId, stream);
                encoder.SetPixelData(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Straight, (uint)wb.PixelWidth, (uint)wb.PixelHeight, 0, 0, bytes);
                await encoder.FlushAsync();
                await stream.FlushAsync();
            }
        }

 

Example of how to scale and crop taken from here:

 

async private void BitmapTransformTest() { // hard coded image location string filePath = "C:\\Users\\Public\\Pictures\\Sample Pictures\\fantasy-dragons-wallpaper.jpg"; StorageFile file = await StorageFile.GetFileFromPathAsync(filePath); if (file == null) return; // 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); // create a new stream and encoder for the new image InMemoryRandomAccessStream ras = new InMemoryRandomAccessStream(); BitmapEncoder enc = await BitmapEncoder.CreateForTranscodingAsync(ras, decoder); // convert the entire bitmap to a 100px by 100px bitmap     enc.BitmapTransform.ScaledHeight = 100;     enc.BitmapTransform.ScaledWidth = 100; BitmapBounds bounds = new BitmapBounds();     bounds.Height = 50;     bounds.Width = 50;     bounds.X = 50;     bounds.Y = 50;     enc.BitmapTransform.Bounds = bounds; // write out to the stream try {         await enc.FlushAsync(); } catch (Exception ex) { string s = ex.ToString(); } // render the stream to the screen BitmapImage bImg = new BitmapImage();     bImg.SetSource(ras);     img.Source = bImg; // image element in xaml  }

 

 

 相关文章：https://stackoverflow.com/questions/12349611/how-to-resize-image-in-c-sharp-winrt-winmd

               http://blog.csdn.net/lindexi_gd/article/details/54612553