13、在 uwp应用中，给图片添加高斯模糊滤镜成效（一）

<TextBlock Text="节约用电" FontSize="30" Foreground="#8800FF00"/>

// 100像素宽，100像素高
WriteableBitmap bitmap = new WriteableBitmap(100, 100);

// 获取表示位图 2D 纹理的数组。
int[] data = bitmap.Pixels;

using (IRandomAccessStream fileStream = await file.OpenAsync(Windows.Storage.FileAccessMode.Read)) 
{
    BitmapDecoder decoder = await BitmapDecoder.CreateAsync(fileStream); 
    // Scale image to appropriate size 
    BitmapTransform transform = new BitmapTransform() {  
        ScaledWidth = Convert.ToUInt32(Scenario4WriteableBitmap.PixelWidth), 
        ScaledHeight = Convert.ToUInt32(Scenario4WriteableBitmap.PixelHeight)
    }; 
    PixelDataProvider pixelData = await decoder.GetPixelDataAsync( 
        BitmapPixelFormat.Bgra8, // WriteableBitmap 使用的是 BGRA 格式 
        BitmapAlphaMode.Straight, 
        transform, 
        ExifOrientationMode.IgnoreExifOrientation, // This sample ignores Exif orientation 
        ColorManagementMode.DoNotColorManage
    ); 
 
    // 包含图片的解码数据。在呈现之前可以被修改
    byte[] sourcePixels = pixelData.DetachPixelData(); 
 
    // 打开一个 image 的流，并且复制到 WriteableBitmap 的 pixel 缓冲区中
    using (Stream stream = writeableBitmap.PixelBuffer.AsStream()) 
    { 
        await stream.WriteAsync(sourcePixels, 0, sourcePixels.Length); 
    }                     
}

 // 把 uwp 的 WriteableBitmap 对象的 PixelBuffer属性（IBuffer）转换为  byte[] 数组
 byte[] colorBytes = BufferToBytes(image.PixelBuffer);

 // 转换为 silverlight 的 int[] 数组时，长度为 byte[] 数组的四分之一
 colorArray = new int[colorBytes.Length / 4];

 int a,r, g, b;
 int i = 0; // 通过 i 自加，来遍历 byte[] 整个数组

 // 通过图片的宽、高，分别设置 int[] 数组中每个像素的 ARGB 信息
 for (int y = 0; y < height; y++)
 {
     for (int x = 0; x < width; x++)
     {
         // int[] 数组的索引
         int index = y * width + x;
         b = colorBytes[i++]; // Blue
         g = colorBytes[i++]; // Green
         r = colorBytes[i++]; // Red
         a = colorBytes[i++]; // Alpha
         colorArray[index] = (a << 24) | (r << 16) | (g << 8) | b;  // 4个 byte值存储为一个 int 值
     }
 }

// 拷贝
WriteableBitmap new_bitmap = await Utility.BitmapClone(wb);

// 添加高斯滤镜效果
MyImage mi = new MyImage(new_bitmap);
GaussianBlurFilter filter = new GaussianBlurFilter();
filter.Sigma = level; 
filter.process(mi);

// 图片添加完滤镜的 int[] 数组
int[] array = mi.colorArray;

// byte[] 数组的长度是 int[] 数组的 4倍
byte[] result = new byte[array.Length * 4];

// 通过自加，来遍历 byte[] 数组中的值
int j = 0;
for (int i = 0; i < array.Length; i++)
{
    // 同时把 int 值中 a、r、g、b 的排列方式，转换为 byte数组中 b、g、r、a 的存储方式 
    result[j++] = (byte)(array[i]);       // Blue
    result[j++] = (byte)(array[i] >> 8);  // Green
    result[j++] = (byte)(array[i] >> 16); // Red
    result[j++] = (byte)(array[i] >> 24); // Alpha
}

// Open a stream to copy the image contents to the WriteableBitmap's pixel buffer 
using (Stream stream = new_bitmap.PixelBuffer.AsStream())
{
    await stream.WriteAsync(result, 0, result.Length);
}

img.Source = new_bitmap;// 把最终 WriteableBitmap 对象赋值给 Image 控件

namespace BlurEffect_demo
{
    class Utility
    {
        /// <summary>
        /// WriteableBitmap 的拷贝
        /// </summary>
        /// <param name="bitmap">原</param>
        /// <returns></returns>
        public static async Task<WriteableBitmap> BitmapClone(WriteableBitmap bitmap)
        {
            WriteableBitmap result = new WriteableBitmap(bitmap.PixelWidth, bitmap.PixelHeight);

            byte[] sourcePixels = Get_WriteableBitmap_bytes(bitmap);

            //byte[] resultPixels = new byte[sourcePixels.Length];

            //sourcePixels.CopyTo(resultPixels, 0);

            using (Stream resultStream = result.PixelBuffer.AsStream())
            {
                await resultStream.WriteAsync(sourcePixels, 0, sourcePixels.Length);
            }
            return result;
        }

        /// <summary>
        /// 获取 WriteableBitmap 对象中的 byte[] 数组数据
        /// </summary>
        public static byte[] Get_WriteableBitmap_bytes(WriteableBitmap bitmap)
        {
            // 获取对直接缓冲区的访问，WriteableBitmap 的每个像素都写入直接缓冲区。
            IBuffer bitmapBuffer = bitmap.PixelBuffer;

            //byte[] sourcePixels = new byte[bitmapBuffer.Length];
            //Windows.Security.Cryptography.CryptographicBuffer.CopyToByteArray(bitmapBuffer, out sourcePixels);
            //bitmapBuffer.CopyTo(sourcePixels);

            using (var dataReader = DataReader.FromBuffer(bitmapBuffer))
            {
                var bytes = new byte[bitmapBuffer.Capacity];
                dataReader.ReadBytes(bytes);
                return bytes;
            }
        }
    }
}