重新想象 Windows 8 Store Apps (29) - 图片处理

浏览数：29 / 时间：2015年06月11日

原文:重新想象 Windows 8 Store Apps (29) - 图片处理

作者：webabcd

介绍
重新想象 Windows 8 Store Apps 之图片处理

显示图片
图片的 9 切片
WriteableBitmap
获取和修改图片属性
对图片文件做“缩放/旋转/编码”操作，并保存操作后的结果

示例
1、演示最基础的图片显示
Image/Display.xaml

<Page
    x:Class="XamlDemo.Image.Display"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:XamlDemo.Image"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="Transparent">
        <StackPanel Margin="120 0 0 0" Orientation="Horizontal" VerticalAlignment="Top">

            <Border BorderBrush="Red" BorderThickness="1" Width="200" Height="100" Margin="20 0 0 0">
                <Image Source="/Assets/Logo.png" Stretch="Uniform" Width="200" Height="100" />
            </Border>

            <Border BorderBrush="Red" BorderThickness="1" Width="200" Height="100" Margin="20 0 0 0">
                <Image Source="ms-appx:///Assets/Logo.png" Stretch="Uniform" Width="200" Height="100" />
            </Border>

            <Border BorderBrush="Red" BorderThickness="1" Width="200" Height="100" Margin="20 0 0 0">
                <Image x:Name="img" Stretch="Uniform" Width="200" Height="100" />
            </Border>

            <Border BorderBrush="Red" BorderThickness="1" Width="200" Height="100" Margin="20 0 0 0">
                <Image x:Name="img2" Stretch="Uniform" Width="200" Height="100" />
            </Border>

        </StackPanel>
    </Grid>
</Page>

Image/Display.xaml.cs

/*
 * 演示最基础的图片显示
 * 
 * 注：
 * 1、引用 package 中的图片用：ms-appx:///
 * 2、引用 ApplicationData 中的图片：
 *    a) LocalFolder 对应 ms-appdata:///local/
 *    b) RoamingFolder 对应 ms-appdata:///roaming/
 *    c) TemporaryFolder 对应 ms-appdata:///temp/
 */

using System;
using Windows.Storage.Streams;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Media.Imaging;
using Windows.UI.Xaml.Navigation;

namespace XamlDemo.Image
{
    public sealed partial class Display : Page
    {
        public Display()
        {
            this.InitializeComponent();
        }

        protected async override void OnNavigatedTo(NavigationEventArgs e)
        {
            // code-behind 指定图片源
            img.Source = new BitmapImage(new Uri("ms-appx:///Assets/Logo.png", UriKind.Absolute));


            // code-behind 指定图片源
            RandomAccessStreamReference imageStreamRef = RandomAccessStreamReference.CreateFromUri(new Uri("ms-appx:///Assets/Logo.png", UriKind.Absolute));
            IRandomAccessStream imageStream = await imageStreamRef.OpenReadAsync();
            BitmapImage bitmapImage = new BitmapImage();
            bitmapImage.SetSource(imageStream);
            img2.Source = bitmapImage;
        }
    }
}

2、演示图片的 NineGrid
Image/NineGrid.xaml

<Page
    x:Class="XamlDemo.Image.NineGrid"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:XamlDemo.Image"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="Transparent">
        <StackPanel Margin="120 0 0 0" Orientation="Horizontal" VerticalAlignment="Top">

            <!--
                Image - 图片控件
                    NineGrid - 指定9网格（相当于flash中的9切片）中的4条线，Thickness 类型
                        Left - 左边的线相对于图片最左端的距离
                        Top - 上边的线相对于图片最顶端的距离
                        Right - 右边的线相对于图片最右端的距离
                        Bottom - 下边的线相对于图片最底端的距离
            
                以下示例图片的原始大小为 16 * 16
            -->

            <Image Source="/Assets/NineGrid/Demo.png" Width="200" Height="200" />

            <!--通过指定9切片，防止边框被放大或缩小-->
            <Image Source="/Assets/NineGrid/Demo.png" Width="200" Height="200" NineGrid="1 1 1 1" Margin="20 0 0 0" />

        </StackPanel>
    </Grid>
</Page>

3、演示 WriteableBitmap 的应用
Image/WriteableBitmapDemo.xaml

<Page
    x:Class="XamlDemo.Image.WriteableBitmapDemo"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:XamlDemo.Image"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="Transparent">
        <StackPanel Margin="120 0 0 0">
            
            <Image x:Name="img" Width="300" Height="300" HorizontalAlignment="Left" />

            <Button x:Name="btnLoadImage" Content="load image" Margin="0 10 0 0" Click="btnLoadImage_Click_1" />

            <Button x:Name="btnChangePixel" Content="加载一个图片并修改其中的像素的颜色值" Margin="0 10 0 0" Click="btnChangePixel_Click_1" />

            <Button x:Name="btnCreatePixel" Content="创建一个图片，设置其每个像素的颜色值" Margin="0 10 0 0" Click="btnCreatePixel_Click_1" />

        </StackPanel>
    </Grid>
</Page>

Image/WriteableBitmapDemo.xaml.cs

/*
 * 演示 WriteableBitmap 的应用
 * 
 * 注：WriteableBitmap 使用的是 BGRA 格式
 */

using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Media.Imaging;
using System;
using System.IO;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Graphics.Imaging;
using Windows.Storage;
using Windows.Storage.Streams;

namespace XamlDemo.Image
{
    public sealed partial class WriteableBitmapDemo : Page
    {
        public WriteableBitmapDemo()
        {
            this.InitializeComponent();
        }


        // 加载一个图片
        private async void btnLoadImage_Click_1(object sender, RoutedEventArgs e)
        {
            // 实例化一个 300*300 的 WriteableBitmap，并将其作为 Image 控件的图片源
            WriteableBitmap writeableBitmap = new WriteableBitmap(300, 300);
            img.Source = writeableBitmap;

            StorageFile file = await StorageFile.GetFileFromApplicationUriAsync(new Uri("ms-appx:///Assets/Logo.png"));
            using (IRandomAccessStream fileStream = await file.OpenAsync(FileAccessMode.Read))
            {
                // 设置 WriteableBitmap 对象的图片流
                await writeableBitmap.SetSourceAsync(fileStream);
            }
        }


        // 加载一个图片并修改其中的像素的颜色值
        private async void btnChangePixel_Click_1(object sender, RoutedEventArgs e)
        {
            // 实例化一个 300*300 的 WriteableBitmap，并将其作为 Image 控件的图片源
            WriteableBitmap writeableBitmap = new WriteableBitmap(300, 300);
            img.Source = writeableBitmap;

            StorageFile file = await StorageFile.GetFileFromApplicationUriAsync(new Uri("ms-appx:///Assets/Logo.png"));
            using (IRandomAccessStream fileStream = await file.OpenAsync(FileAccessMode.Read))
            {
                // 将指定的图片转换成 BitmapDecoder 对象
                BitmapDecoder decoder = await BitmapDecoder.CreateAsync(fileStream);

                // 通过 BitmapTransform 缩放图片的尺寸
                BitmapTransform transform = new BitmapTransform()
                {
                    ScaledWidth = Convert.ToUInt32(writeableBitmap.PixelWidth),
                    ScaledHeight = Convert.ToUInt32(writeableBitmap.PixelHeight)
                };

                // 获取图片的 PixelDataProvider 对象
                PixelDataProvider pixelData = await decoder.GetPixelDataAsync(
                    BitmapPixelFormat.Bgra8,
                    BitmapAlphaMode.Straight,
                    transform,
                    ExifOrientationMode.IgnoreExifOrientation, 
                    ColorManagementMode.DoNotColorManage);

                // 获取图片的像素数据，由于之前指定的格式是 BitmapPixelFormat.Bgra8，所以每一个像素由 4 个字节组成，分别是 bgra
                byte[] sourcePixels = pixelData.DetachPixelData();
                for (int i = 0; i < sourcePixels.Length; i++)
                {
                   sourcePixels[i] -= 10;
                }

                // 将修改后的像素数据写入 WriteableBitmap 对象的像素缓冲区（WriteableBitmap 使用的是 BGRA 格式）
                using (Stream stream = writeableBitmap.PixelBuffer.AsStream()) // IBuffer.AsStream() 为来自 System.Runtime.InteropServices.WindowsRuntime.WindowsRuntimeBufferExtensions 中的扩展方法
                {
                    await stream.WriteAsync(sourcePixels, 0, sourcePixels.Length);
                }
            }

            // 用像素缓冲区的数据绘制图片
            writeableBitmap.Invalidate();
        }
        

        // 创建一个图片，设置其每个像素的颜色值
        private async void btnCreatePixel_Click_1(object sender, RoutedEventArgs e)
        {
            // 实例化一个 300*300 的 WriteableBitmap，并将其作为 Image 控件的图片源
            WriteableBitmap writeableBitmap = new WriteableBitmap(300, 300);
            img.Source = writeableBitmap;

            Random random = new Random();

            // 设置需要绘制的图片的像素数据（每一个像素由 4 个字节组成，分别是 bgra）
            byte[] result = new byte[300 * 300 * 4];
            for (int i = 0; i < result.Length; )
            {
                result[i++] = (byte)random.Next(0, 256); // Green
                result[i++] = (byte)random.Next(0, 256); // Blue
                result[i++] = (byte)random.Next(0, 256); // Red
                result[i++] = 255; // Alpha
            }

            // 将像素数据写入 WriteableBitmap 对象的像素缓冲区
            using (Stream stream = writeableBitmap.PixelBuffer.AsStream())
            {
                await stream.WriteAsync(result, 0, result.Length);
            }

            // 用像素缓冲区的数据绘制图片
            writeableBitmap.Invalidate();
        }
    }
}

4、演示如何获取、修改图片属性
Image/ImageProperty.xaml.cs

/*
 * 演示如何获取、修改图片属性
 */

using System;
using System.Threading.Tasks;
using Windows.Storage;
using Windows.Storage.FileProperties;
using Windows.Storage.Pickers;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Navigation;
using XamlDemo.Common;

namespace XamlDemo.Image
{
    public sealed partial class ImageProperty : Page
    {
        public ImageProperty()
        {
            this.InitializeComponent();
        }

        protected async override void OnNavigatedTo(NavigationEventArgs e)
        {
            if (Helper.EnsureUnsnapped())
            {
                // 选择一个图片文件
                FileOpenPicker picker = new FileOpenPicker();
                picker.SuggestedStartLocation = Windows.Storage.Pickers.PickerLocationId.PicturesLibrary;
                picker.FileTypeFilter.Add(".jpg");
                picker.FileTypeFilter.Add(".png");

                StorageFile file = await picker.PickSingleFileAsync();

                if (file != null)
                {
                    ImageProperties imageProperties = await GetImageProperty(file);
                    UpdateImageProperty(imageProperties);
                }
            }
        }

        // 获取图片属性
        private async Task<ImageProperties> GetImageProperty(StorageFile file)
        {
            // 获取图片文件的图片属性信息
            ImageProperties imageProperties = await file.Properties.GetImagePropertiesAsync();

            // 显示图片文件的图片属性（以下试举几例，不全）
            lblMsg.Text = "title: " + imageProperties.Title;
            lblMsg.Text += Environment.NewLine;
            lblMsg.Text += "keywords: " + string.Join(",", imageProperties.Keywords);
            lblMsg.Text += Environment.NewLine;
            lblMsg.Text += "width: " + imageProperties.Width;
            lblMsg.Text += Environment.NewLine;
            lblMsg.Text += "height: " + imageProperties.Height;
            lblMsg.Text += Environment.NewLine;

            return imageProperties;
        }

        // 更新图片属性
        private async void UpdateImageProperty(ImageProperties imageProperties)
        {
            Random random = new Random();

            // 设置图片文件的图片属性（以下试举几例，不全）
            imageProperties.Title = random.Next(0, 1000).ToString();
            imageProperties.Keywords.Clear();
            imageProperties.Keywords.Add(random.Next(0, 1000).ToString());
            imageProperties.Keywords.Add(random.Next(0, 1000).ToString());

            try
            {
                // 保存图片文件的图片属性信息
                await imageProperties.SavePropertiesAsync();
                lblMsg.Text += "title 和 keywords 已被修改，重新进来可看效果";
            }
            catch (Exception ex)
            {
                lblMsg.Text = ex.ToString();
            }
        }
    }
}

5、演示如何对图片文件做“缩放/旋转/编码”操作，并保存操作后的结果
Image/ImageTransform.xaml

<Page
    x:Class="XamlDemo.Image.ImageTransform"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:XamlDemo.Image"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="Transparent">
        <StackPanel Margin="120 0 0 0">

            <Image x:Name="imgOriginal" Stretch="Uniform" Width="300" Height="200" HorizontalAlignment="Left" />

            <Image x:Name="imgTransformed" Stretch="Uniform" Width="300" Height="200" HorizontalAlignment="Left" Margin="0 10 0 0" />

        </StackPanel>
    </Grid>
</Page>

Image/ImageTransform.xaml.cs

/*
 * 演示如何对图片文件做“缩放/旋转/编码”操作，并保存操作后的结果
 */

using System;
using Windows.Graphics.Imaging;
using Windows.Storage;
using Windows.Storage.Pickers;
using Windows.Storage.Streams;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Media.Imaging;
using Windows.UI.Xaml.Navigation;
using XamlDemo.Common;

namespace XamlDemo.Image
{
    public sealed partial class ImageTransform : Page
    {
        public ImageTransform()
        {
            this.InitializeComponent();
        }

        protected async override void OnNavigatedTo(NavigationEventArgs e)
        {
            if (Helper.EnsureUnsnapped())
            {
                // 选择一个 .jpg 图片文件
                FileOpenPicker picker = new FileOpenPicker();
                picker.SuggestedStartLocation = Windows.Storage.Pickers.PickerLocationId.PicturesLibrary;
                picker.FileTypeFilter.Add(".jpg");

                StorageFile fileRead = await picker.PickSingleFileAsync();

                if (fileRead != null)
                {
                    // 显示用户选中的图片文件
                    BitmapImage src = new BitmapImage();
                    src.SetSource(await fileRead.OpenAsync(FileAccessMode.Read));
                    imgOriginal.Source = src;


                    // 定义一个转换后的图片文件
                    StorageFile fileWrite = await ApplicationData.Current.TemporaryFolder.CreateFileAsync(@"webabcdTest\imageTransformDemo.png", CreationCollisionOption.ReplaceExisting);


                    using (IRandomAccessStream inputStream = await fileRead.OpenAsync(FileAccessMode.Read), outputStream = await fileWrite.OpenAsync(FileAccessMode.ReadWrite))
                    {
                        // 将用户选择的图片文件转换为一个 BitmapDecoder 对象
                        BitmapDecoder decoder = await BitmapDecoder.CreateAsync(inputStream);

                        // 通过 BitmapTransform 来配置图片的宽度、高度和顺时针旋转角度
                        BitmapTransform transform = new BitmapTransform();
                        transform.ScaledWidth = 100;
                        transform.ScaledHeight = 100;
                        transform.Rotation = BitmapRotation.Clockwise180Degrees;

                        // 获取图片的 PixelDataProvider 对象
                        PixelDataProvider pixelProvider = await decoder.GetPixelDataAsync(
                            decoder.BitmapPixelFormat,
                            decoder.BitmapAlphaMode,
                            transform,
                            ExifOrientationMode.RespectExifOrientation,
                            ColorManagementMode.ColorManageToSRgb
                        );

                        // 获取经过了 BitmapTransform 转换后的图片的像素数据
                        byte[] pixels = pixelProvider.DetachPixelData();

                        // 创建一个 BitmapEncoder 对象，可以指定图片的编码格式（PngEncoderId, JpegEncoderId, JpegXREncoderId, GifEncoderId, TiffEncoderId）
                        BitmapEncoder encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, outputStream);

                        // 转码像素数据到指定的图片编码格式（本例会转吗为 png 格式），并将转码后的数据写入 stream 缓冲区
                        encoder.SetPixelData(
                            decoder.BitmapPixelFormat,
                            decoder.BitmapAlphaMode,
                            100,
                            100,
                            decoder.DpiX,
                            decoder.DpiY,
                            pixels
                        );

                        // 提交 stream 缓冲区中的所有内容
                        await encoder.FlushAsync();
                    }

                    // 显示经过“缩放/旋转/编码”操作后的图片文件
                    imgTransformed.Source = new BitmapImage(new Uri("ms-appdata:///temp/webabcdTest/imageTransformDemo.png", UriKind.Absolute));
                }
            }
        }
    }
}